CARLA PLANA OLIVARES

DIEGO MOLINA SERRANO

3 ESO A2
2022-23
Unit 3: Nutrition: the digestive and respiratory systems.

1. The digestive system---------------------------------------------------- 3

2. Digestive processes------------------------------------------------------ 6
3. Principal diseases of the digestive system------------------------- 8
4. Healthy habits for the digestive system--------------------------- 10
5. The respiratory system------------------------------------------------ 12
6. How the respiratory system works-------------------------------- 15
7. Diseases of the respiratory system--------------------------------- 18
8. Practice 5: Lungs dissection----------------------------------------- 22
9. Practice 6: qüestionari del sistema respiratori------------------ 24

Unit 4: Nutrition: the circulatory and excretory systems.

1. The internal environment and the circulatory system------ 26

2. The lymphatic system-------------------------------------------------28
3. Blood----------------------------------------------------------------------- 30
4. Blood vessels------------------------------------------------------------- 32
5. The heart------------------------------------------------------------------ 34
6. The double circulatory system------------------------------------- 38
7. Cardiovascular diseases----------------------------------------------- 39
8. Diseases and disorders of the blood------------------------------- 40
9. Healthy habits for the circulatory system----------------------- 42
10.Excretion------------------------------------------------------------------ 45
11.Diseases of the excretory system. Healthy habits.------------ 48
12.Practice 7 Heart dissection----------------------------------------- 51
13.Pràctica 8: Qüestionari del sistema circulatori--------------- 53
Nutrition: the digestive and respiratory systems

The digestive system transforms food into nutrients that are the right size to reach the body and be
absorbed.
To carry out this function, the digestive system consists of a group of organs and structures: the
digestive tract and the accessory glands.

The digestive tract

 2

Mouth: The entry point of the digestive tract. It contains:

- Teeth, to bite and break food into small pieces.
- A tongue, to mix and swallow food as well as enable the sense of taste.
- The salivary glands.

Pharynx: A cavity shared by the digestive and respiratory systems. Air passes toward the larynx and
food passes toward the oesophagus.
- The epiglottis is a small, flexible cartilage, it’s a valve that closes one and another of the
tubes.

Oesophagus: A tube with a length of 25 cm.

- Is made of smooth muscle, it has a slow and involuntary contraction. The food travels
through the tube little by little and makes a peristaltic movement.
- It connects the pharynx with the stomach.

Stomach: A wide part of the digestive tract found in the abdominal cavity.
- Two valves regulate the flow of food: the cardia, at the entry point, and the pylorus, at the
exit point.
- The stomach is small and elastic.
- Walls that are not smooth, the stomach closes the valves and begins to secrete gastric juices
and secretes hydrochloric acid, a strong, corrosive acid. This is called the digestion process.
- It generates mucus and prevents the acid from attacking the walls of the stomach, without
this mucus it would burn. The valve opens and descends to the small intestine.

Small intestine: 6 meters of intestine in the abdominal cavity.

- It is divided into three segments: duodenum, jejunum and ileum.
- It has many folds with glands that secrete intestinal juice.

Large intestine: The last section of the digestive tract.

- It has a length of 1,5 m, which surrounds the small intestine.
- It is differentiated into three parts: the cecum, where we also find the appendix, if it breaks
it can be fatal, the colon and the rectum.
- The colon is divided into three segments: ascending, transverse and descending.
- The rectum terminates in the anus.
 The accessory glands

Unlike the gastric juices and intestinal glands, the accessory glands are located outside the digestive
tract. They produce digestive juices are secrete them into the tract. These juices contain digestive
enzymes, proteins that help to break down different nutrients, decomposing organic
macromolecules in their components.

The accessory glands consist of:

Salivary glands: They produce and secrete saliva into the mouth.
- The three main pairs of glands are the sublingual, located under the tongue; the
submandibular, located in the jaw; and the parotids, located close to the ears.

Pancreas: It is long, flat organ located below the stomach that secretes pancreatic juice into the
duodenum.
- It also produces substances that are involved in the metabolism of glucose. These
substances are released directly into the bloodstream.

Liver: It is the largest accessory gland. It has several functions:

- It synthesizes proteins.
- It regulates the metabolism of glucose.
- It stores vitamins and minerals.
- It processes alcohol and drugs found in the blood in order to eliminate them.
- It produces bile. This stored in the gall bladder before it is secreted into the duodenum. Bile
contains bile salts that facilitate the digestion and absorption of lipids.
As food moves through the digestive tract, several organs take part in four digestive processes:
ingestion, digestion, absorption and formation of faeces.

The first three processes transform food into nutrients using two types of actions:
Mechanical: We chop the food with our mouths (we move it)
Chemical: Chemical digestion, which with the digestive juices, breaks everything we eat into
molecules. We break down the macromolecules that make up food, we break down proteins into
amino acids, for example.

Ingestion

Mastication or chewing. We chew to make food smaller.

Insalivation: The mixing of saliva with food in the mouth. The tongue helps to give the mixture a
ball-like shape called a bolus.
Swallowing: The tongue pushes the bolus from the mouth into the pharynx. The bolus moves
through the pharynx to the esophagus. There, wall muscles produce wave-like contractions called
peristalsis. These contractions move the bolus toward the stomach.
* Peristalsis is the act of squeezing the esophagus so that food can be transported.

Digestion

Digestion takes place in the organs of the digestive tract:

Place Juice Enzym Biomolecule that

process

Mouth Saliva Amylases Glucids

Stomach Hydrochloric acid Pepsin Protein

(HCL)

Small intestine Bile Lipases Lipids

Pancreatic juice Amylases Glucids
Intestinal juice Peptidases Proteins
*Enzy (specialized biomolecule that breaks other molecules, molecule scissors.)
Absorption

In this process, the nutrients obtained during digestion pass through the walls of the digestive
system to the blood, where they are transported to the cells. This process takes place in both the
small intestine and the large intestine, which is why it is called intestinal absorption.

In the small intestine, is very long and is folded inside our body, twice and inside our bile we have
more and small folds. In this, absorption of simple glucids, fatty acids and amino acids takes place
primarily and water, salts and vitamins are also absorbed here.
The small intestine has thin walls and a large surface area increased by intestinal folds. These folds
have tiny finger-like protrusions called villi. The villi have protrusions called microvilli. All of these
protrusions increase the surface area where nutrients can be absorbed.

In the large intestine, water, mineral salts and vitamins are absorbed. The intestinal flora produces
nutrients such as vitamin K that are absorbed by the cells of the colon.

Formation of faeces

Some foods that cannot be digested are converted into waste to be eliminated by the digestive tract.
This waste is compacted in the large intestine, where it loses water and mineral salts. Bacterial flora
feed upon part of these substances.

As a result, faeces are formed and accumulate in the final section of the large intestine. They are
expelled during defecation.

- Fibre is sugar and since we can't break it down, we reject it.

- We must eat fibre to improve intestinal transit, but we cannot digest it.
- Everything we can't digest is converted with feces.
Any organ in the human body can stop functioning normally and any time. This can use problems
or even disease. Sometimes the malfunction is the result of a lack of hygiene or poor eating habits.
Understanding some of the diseases of the digestive system can help to prevent them.

Caries, or tooth decay, is an infectious disease caused by bacteria called sterptococcus mutans that
live in the mouth. They feed on the remains of food found there, especially the glucids from sugary
food. As a result, acids are produced that weaken dental enamel and cause small holes. The acids
erode the dentine and reach the pulp.

Peptic ulter, disease caused by a bacterium called helicobacker pylori that affects the stomach or
the duodenum and causes bleeding, if the infection lasts a long time we can have a perforation of
the stomach. Alcohol, smoking and drugs aggravate the disease.

Gastroenteritis, an inflammation or swelling of the stomach or the small intestine, generally

produced by an infection. There are two types of gastroenteritis: stomach and intestinal. The cause
of this infection can be food poisoning, contact with people already affected, viruses and bacteria
(cholera). The main symptoms are vomiting and diarrhoea, stomach pains, fever, headache and
chills. Dehydration is the principal problem, so the intake of liquids must be increased.
Appendicitis, when the appendix is ​opened, food gets inside, causing the appendix to rupture or
become infected. The consequences can be very serious if not treated quickly.

Constipation, difficult defecation, often caused by stress or diets lacking in fibre and water. These
conditions lead too hard, dry faeces that make defecation difficult.

Hepatitis, an inflammation of the liver caused by a virus, toxins, poisonous substances, certain
medicines or alcohol.
In order to have a healthy digestive system, follow these guidelines. Making them part of your
everyday life can help to prevent.

Eat food rich in fibre, fibre isn’t digested, but it facilitates intestinal movement, which in turn
prevents constipation.

Eat slowly and chew well, this enables the enzymes in the digestive juices to work better.
Maintain a regular eating schedule, and eat five light meals a day. In this way, the digestive
system isn’t forced to work extra.

Don’t drink alcohol, regular consumption of alcohol damages the liver and the pancreas, and can
cause serious illnesses. It does not provide vitamins and has many calories. It's very bad.

Drink water, your body needs to replace body fluids to function properly. Two litres a day is
advisable.
Wash your hands, before eating. You should also wash food, especially food that is eaten raw. This
way, food will not be contained by anything that might harm your body. So that bacteria do not
enter the food, wash your hands and cut the different types of food on different tables.

Practice sport, regularly. This helps to prevent constipation.

Prevent tooth decay, eat a healthy diet. Too much sugar is a major cause of caries. Brush your
teeth three times a day and visit your dentist at least once a year.

Be careful when you travel, in order to prevent diarrhoea. Don’t eat fresh vegetables or fruit
without first peeling them. Food that is not well cooked, cakes and sweets can be easily
contaminated. Drink only bottled water and don’t put ice cubes in your drinks.
The human body needs to obtain oxygen and transport it to the cells. This allows cells to carry out
the metabolic reactions necessary to stay alive. The respiratory system enables oxygen in the air to
enter the body and pass into the bloodstream. This system is also responsible for expelling carbon
dioxide, a waste product of cellular respiration, from the body.
The respiratory system consists of the respiratory tract and the lungs.

The respiratory tract

Nasal passages: The air enters through the nose and continues through these passages, where it is
moistened and warmed. Dust, microorganisms or harmful particles from the air are retained here.

Pharynx: It is shared with the digestive system. Air from the nasal passages reaches the pharynx.
When you eat or swallow saliva, the epiglottis closes to prevent food from entering the trachea.

Larynx: It is exclusive to the respiratory system. A short tube made of cartilage. When air passes
through the larynx, the vocal cords vibrate. This allows humans to make sounds.
Trachea: A short, flexible tube made of C-shaped rings of cartilage through which air travels from
the larynx to the bronchi. The trachea is elastic because it is not tight, it must always maintain a
certain diameter. The inside of this tube is lined with cells that have hair-like projections. These
cells have a constant flow of mucus into the pharynx. This mucus removes dust and
microorganisms.

Bronchi and bronchiles: The bronchi are two tubes that leave the trachea in each lung. Inside the
lungs, they continue to divide and become smaller tubes called bronchioles. They are very thin
passages that end in small rounded sacs with very thin walls called alevoli pulomonar. Many times
the mucus (residue) is expelled and other times it is swallowed.

The lungs

The lungs are a pair of spongy organs located in the chest cavity on either side of the heart. They are
protected by the ribs. There are small differences in their size and shape. They contain tissue, veins
and are full of air cavities.

We need the lungs to carry out gas exchange, which reaches our cells, to be able to carry out the
process of cellular respiration. We exchange gases, taking in oxygen and expelling carbon dioxide.
Oxygen allows cellular respiration. Some of the animals do not have a respiratory system that does
not allow oxygen to reach their cells, because they do not need to have complex systems.

Left lung, it is the smaller of the two and has two lobes.
Right lung, it is a little larger and is divided into three lobes.

One lung is larger than the other in order to leave the necessary space on the left side where the
heart is roughly displaced.

Both lungs are surrounded by two membranes called the pleura. The pleura protect the surface of
the lungs from damage as they move inside the thoracic cavity. Inside the pleura, pleural fluid
enables the lungs to move easily during breathing.

The bronchi and bronchioles in each lung from a bronchial tree that ends the pulmonary alveoli.
The alveoli are grouped in alveolar sacs that give the lungs their spongy appearance.
We have millions of alveoli, they are very small and close together.
They are found in the branches of the lungs. They always have a vein and an artery (they are
covered).
Unlike the other arteries and veins in the body, the pulmonary arteries carry deoxygenated blood to
the lungs. The pulmonary veins that leave the lungs carry oxygenated blood. They follow a parallel
path to the bronchi and bronchioles.

Total lung capacity (TLC) is the maximum volume of air the lungs can hold. The normal volume
is about 6L. Air volume is measured using a spirometer. Lung capacity is very important for
long-distance (endurance) athletes. It can be trained, however, genetically you already have this
ability.
Respiration consists of two separate phases: ventilation and gas exchange.

Pulmonary ventilation

This also called breathing. It is the movement of air in and out the lungs. Air is a gas that tries to
occupy the largest possible volume.

It consists of two consecutive involuntary movements:

In inhalation, oxygen-rich air enters the lungs through the respiratory tract.
In exhalation, carbon dioxide-rich air exits the lungs and reaches the outside. When you breathe,
the thoracic cavity moves rhythmically. During inhalation, the lungs, located directly next to the
thoracic cavity, expand and fill with air. During exhalation, air leaves the lungs as the thoracic cavity
contracts.

The lungs don't have muscles. They fill with air and then expel it thanks to several muscles in the
abdomen:

The diaphragm, dome-like in shape, separates the thoracic cavity from the abdominal cavity.
The intercostal muscles, located between the ribs, keep the ribs together.
Gas exchange

Gas exchange takes place in the pulmonary alveoli. The alveoli are surrounded by a network of
capillaries that bring blood, rich in carbon dioxide and low oxygen, from all the body. The blood
that comes from the lungs has carbon dioxide and that's why it has this dark colour.

Lungs have 300-400 million alveoli. The surface area that they provide for gas exchange is
approximately 150-200 m2. This about the size of a tennis court.

When the inhaled, oxygen-rich air reaches the pulmonary alveoli, a process of intense, rapid gas
exchange takes place. During this process, the blood flowing through the capillaries discharges the
carbon dioxide it has collected from the tissue cells. At the same time, the blood absorbs oxygen
obtained from breathing, which it then carries to these same cells.

The gases pass between the alveoli and blood capillaries due to the large difference in the
concentration of gases between them. A gas always passes from a region of higher concentration to
a region of lower concentration. Gases pass through the membranes of the alveolar epithelial cells
and the capillary endothelium by simple diffusion because oxygen and carbon dioxide are small
molecules.

Red blood cells, or erythrocytes, carry a large

amount of haemoglobin (Hb), a protein that
transports gases. Due to the presence of iron
atoms in this protein, it is red.

The concentration of CO2 in the blood is

higher than in the alveoli, which have a high
percentage of O2. Gas exchange occurs by
diffusion. The CO2 passes into the body
through the respiratory tract.

As the Hb absorbs O2, oxyhaemoglobin

(HbO2), it becomes are more intense rest.
The O2 is transported to every cell in the
body.
The arteries are the ones that contain the carbon dioxide and the veins are the ones that contain the
oxygen.
If the carbon dioxide increases and the oxygen is the same, our bodies are affected because the
blood will not be able to go out and there will be no gas exchange, therefore we cannot breathe.

Why does blood or plasma not come out and carbon dioxide does? Semi-permeable membranes
that let some things through and others not.
Diseases of the respiratory system. Healthy habits.

Asthma: A narrowing of the bronchial tubes due to:

- Contraccion of the bronchial wall.
- Inflammation of the mucosa.
- Excess mucus. Breathing becomes difficult.

Allergic rhinitis: An inflammation of the nasal mucosa because of an allergy to:

- Polen.
- Dust mites.
- Animal dander, etc.
Congestion, sneezing and an itchy nose or throat result.

Pharyngitis and tonsillitis: An inflammation of the pharynx and of the tonsils due to
microorganisms. The main symptoms are:
- Localized pain.
- Increased mucus.
- Fever (occasionally).
- Coughing.

Pneumonia: An inflammation of the lung tissue due to bacterial or viral infection. The main
symptoms are:
- Difficulty in breathing.
- A high fever.
It is treated with antibiotics but can cause death.
Colds and flu: Infections of the respiratory tract due to a virus:
- Colds and flu produce nasal obstruction, sneezing, coughing, abundant mucus and general
discomfort.
- The flu also produces muscular pain, chills and fever.

Bronchitis: Inflammation of the bronchial mucosa due to bacteria, microorganisms, virus or

irritants.
The main symptoms are:
- Difficulty in breathing.
- A wheezing cough with yellow-green phlegm.
- Aches and pains.

Lung cancer: Tumour or unusual cell growth in the bronchial tubes and lung tissue.
The main symptoms are:
- The lungs stop functioning correctly.
- Pain and possibly death.
Smoking is a major cause of the disease.

Pulmonary emphysema: Enlargement of the alveoli caused by wakened, torn walls.

The main symptoms are:
- Breathing becomes progressively limited,
almost permanently.
Smoking and pollution are major causes.
Healthy habits for the respiratory system

These habits help to keep the respiratory system healthy:

Create a healthy environment at home, be careful when using chemical products that can
irritate the respiratory tract. Ventilate your bedroom every day for at least ten minutes. Keep it
clean of dust and the dust mites that cause many allergies.

Exercise moderately and regularly, exercise improves your quality of life, strengthens your body
and helps it grow. For example, it increases your lung capacity. This improves how you respond to
an unexpected or accidental situation. Regular exercise also prevents or delays the appearance of
diseases. Aerobic exercise, such as walking, riding a bicycle, swimming, jogging and running,
improves lung capacity and pollutants from the air.

Avoid places that are polluted, poorly ventilated or crowded, in places like these, breathe
through your nose. This filters microorganisms and pollutants from the air.
Don’t smoke!, stay away from people when they are smoking.

Smoking - a dangerous habit

Smoking is an addiction that directly causes many respiratory diseases. It also makes the symptoms
of many other diseases worse. That is, it has a negative effect on diseases of the respiratory,
circulatory and nervous systems.

Tobacco has been consumed for over 500 years. However, it is only in recent decades that the
tremendous damage it causes the body both directly and indirectly has been demonstrated.
Smoking kills almost six million people every year. About 10% of them are non-smokers.

Analysis of cigarette smoke reveals over 4,000 different chemical substances. Nicotine, carbon
monoxide and tar are the most abundant, and the most dangerous due to their effects on the body.

Nicotine Carbon monoxide Tar

This toxic substance makes A very poisonous gas that A mixture of substances that
smoking addictive. Even enters the bloodstream easily. is deposited on the cilia of the
through smokers know that It links to haemoglobin and respiratory tract. It prevents
this habit is dangerous, their impedes the transport of them from cleaning the
feel compelled to smoke. For oxygen. This is why smokers airways. This can lead to
this reason, nowadays, become tired more quickly. chronic bronchitis,
tobacco is considerate a drug. emphysema and cancer of the
mouth, the respiratory tract
and the lungs: 90% of all lung
cancer is caused by smoking.
The younger a person begins
to smoke, the longer he or she
smokes, and the more likely
cancer will develop.
PRACTICE Nº5: Lung dissection
We will use a sheep's lungs to study the anatomy of the respiratory system. It is
interesting to study the lungs together with the heart, as we can observe the
relationship between the organs and the blood vessels.

Materials (list the material we used)

■ Sheep lungs.
■ Scalpel.
■ Pair of scissors.
■ Gloves.
■ Straws.
■ Dissecting tray.

Procedure
Place the lungs in the dissection tray and identify the trachea, the bronchi and the
pulmonary lobes. The lobes can be more easily identified by inserting a tube through
the trachea and blowing.

Touch the surface of the lungs with your finger. What does it feel like? Describe the shape
and color of the lungs.

When I touched, I noticed that the lung has a slimy texture. They have a shape similar to an
abstract cone. One of the lungs, specifically the right one, is slightly larger than the left one.
They have a light pink colour.
Compare the left and right lungs. What differences do you observe? What do you think
explains these differences?
As I said in the previous exercise, the difference observed between the two lungs is that the
right is larger than the left. Those differences explain that the heart is slightly on the left side
and needs space, so in order for it to be there, the left lung is smaller.
Observe the trachea. What is it like? What types of tissue form it? Do you think there is
any relationship between the function performed by the trachea and its morphology?
The trachea resembles a tube that separates into two branches, called bronchi. The tissue that
forms the trachea is a mucous epithelial tissue. I think it's related, as the tube-like trachea
allows air to move during breathing correctly and easily, as indicated by its function.
Using the scissors, cut the trachea open lengthwise up to its branches: the bronchi. Observe
the inside part and feel inside with your finger. Describe its appearance and texture. Why is
there mucus in the inner side? Where is this mucus formed? Do you notice any differences
between the trachea and the bronchus? Which ones? Keep opening the bronchus and
describe what you notice.
The texture and appearance that I notice when cutting the trachea to find the bronchi is
gelatinous and slimy. There is mucus because the inside is lined with cells that produce that
mucus. That mucus forms in membranes that go from the nose to the lungs. Yes, I notice
differences. The difference is that the trachea is a fairly large tube and the bronchi are a kind
of much smaller tubes that branch out, another the difference is that the trachea conducts air
to the bronchi, and they are the ones that carry air to the lungs. The bronchus is a smaller tube
with a very rough and hard texture.
There are two tubes that run parallel to the bronchus: an artery and a vein. Try to locate
them.
Cut one of the pulmonary lobes transversely. Split opens the two parts and find the pleura
and the tubes that appear after cutting: the veins, arteries and bronchi. Test the elasticity of
the lobe by pressing down on it with your hand.

Cut a piece of lung and immerse it in a beaker of water. What happens? What is the reason?
When you put a piece of the lung in the beaker of water, the lung floats. This is because the
lung is made of air, which has less density than water.
Draw a diagram identifying the different parts of the lungs.
PRÀCTICA 6: EL SISTEMA RESPIRATORI
1. Per a fer quines accions necessita el nostre cos l'oxigen?

El nostre cos necessita l'oxigen per a produir energia, créixer, reparar-se i mantenir
les seves funcions vitals.

2. Quines són les parts del sistema respiratori?

Les parts del sistema respiratori són les foses nasals, els cilis, els pits paranasals, la
faringe (on trobem també, l’epiglotis) la laringe (on trobem, les cordes vocals), la
tràquea, els bronquis i, les seves ramificacions que reben el nom de bronquíols i
finalment, els pulmons.

3. Per què hem d'eliminar el CO2?

Hem d’eliminar el CO₂ perquè és un producte de rebuig del metabolisme de les

nostres cèl·lules i ens pot provocar malalties perjudicials.

4. Quina funció tenen les foses nasals?

Les foses nasals fan la funció d'escalfar i humitejar l’aire.

5. Quina és la funció del moc?

La funció del moc és actuar com a una barrera per filtrar l’aire de la pols i els
organismes infecciosos.

6. Descriu el camí que segueix l'aire fins als pulmons.

L’aire entra pels orificis nasals fins a les fosses nasals, unes cavitats on l’aire
s’escalfa i s’humiteja, després, l’aire travessa una membrana amb minúsculs
filaments, petits pèls anomenats cilis que amb l'ajuda del moc fan de barrera per les
partícules infeccioses o pols que pot entrar junt amb l’aire. Seguidament, passa
també per altres cavitats ubicades al voltant dels ulls, que reben el nom de pits
paranasals que ajuden a agafar a l’aire, la temperatura corporal (uns 37 graus) i
col·laboren amb el filtratge. L’aire segueix el seu camí, fins a arribar a parar a la
faringe i, es divideix en dos conductes diferents, per un costat l’esòfag que és part
de l’aparell digestiu i per l’altre, la laringe, que és per on viatja l’aire fins als pulmons.
En tragar un aliment, la laringe es desplaça cap a dalt i l’epiglotis que és el cartílag
per on passa, es mou i fa la funció d’una xemeneia, ja que no deixa passar els
aliments perquè arribin als pulmons. L’aire baixa per la tràquea fins a arribar als
bronquis on es produeixen unes ramificacions que reben el nom de bronquíols que
desembocaran en els alvèols on arribarà l’aire i es produirà l'hematosi que
incorporarà l'oxigen perquè puguem respirar i eliminarà la substància de rebuig, el
diòxid de carboni. Per la seva banda, les artèries i les venes són responsables de
transportar la sang desoxigenada des del cor cap als pulmons, així com la sang
oxigenada des dels pulmons cap al cor, respectivament.
7. Com són les cordes vocals? Com funcionen?

Les cordes vocals són plecs membranosos de forma rectangular i de color blanc. Si
s’obren i es recullen cap als costats, l’aire passa lliurement sense fer pressió i així
respirem. Si s’ajunten, l’aire passa entre elles i inicia un moviment molt ràpid de
vibració amb el qual es produeix el so que anomenem veu.

8. Quin tipus de teixit cobreix l'interior de la tràquea i els bronquis?

El teixit epitelial mucós cobreix l’interior de la tràquea i els bronquis.

9. Com es diu el menjar quan arriba a l'estómac?

El menjar quan arriba a l’estómac s’anomena quim.

10. Quant pesa cada pulmó?

Cada pulmó pesa un quilogram i mig cadascú.

11. Com es diuen les membranes que cobreixen als pulmons? Què contenen?

Les membranes que cobreixen els pulmons es diuen pleura visceral i l’interior de la
caixa toràcica, per una altra membrana anomenada pleura parietal. Entre elles
contenen líquid pleural que permet que els pulmons rellisquin sense problema a la
respiració.

12. Quant aire agafem amb cada inspiració?

Agafem aproximadament mig litre d’aire a cada inspiració.

13. Quants alvèols tenim en els pulmons?

Als pulmons tenim entre 200 i 700 milions d’alvèols.

14. Quina molècula transporta l'O2 i el CO2?

L'hemoglobina transporta l’oxigen molecular i el diòxid de carboni.

15. Per què hi ha sempre un volum d'aire residual dins dels pulmons?

Perquè els alvèols tinguin major facilitat per incorporar l’oxigen.

Nutrition: the circulatory and excretory system

Internal environment refers to the fluids that surround the cells in the body.
Homeostasis: It is the conditions of the internal environment, such as temperature and fluid
composition, that are stable for cells to function properly. It is maintained by the organ systems of
the body. Every time these conditions change we will be sick or in discomfort.

The internal human environment consists of:

- Interstitial fluid (plasma). It surrounds and bathes the cells.
- Blood and lymph. They collect and distribute substances the cells need, and eliminate
waste from the cells through the circulatory system.

The circulatory system consists of two systems: the blood circulatory system and the lymphatic
system.
- The blood circulatory system. It is carries nutrients and oxygen throughout the body
and collects metabolic wastes for elimination.

It is characterized by having blood. Transport of oxygen and CO₂.

Carbohydrate (glucid)+ O2 ---- CO2+H2O
C6H12O6 -------------------Lungs, kidney
NH3
Urine

- The lymphatic system. It has three main functions:

- Return excess interstitial fluid to the blood.
- Transport absorbed fat from the small intestine to the blood.
- Defend the body in the immune system.
 The clear, whitish circulating fluid in the lymphatic system is called lymph.

The circulatory system and homeostasis

1. Nutrients and oxygen from the blood in the capillaries are released into the interstitial fluid,
changing its composition.
2. Next, the cells take oxygen and nutrients from the interstitial fluid. This results in excess fluid.
3. Excess interstitial fluid is collected by the lymphatic system. Homeostasis is restored. The
organism functions properly.
The lymphatic system is a network of vessels and structures distributed throughout the body.
Smaller vessels join to form larger ones.

It doesn't carry oxygen because it doesn't carry red blood cells that stay inside the capillaries, but the
plasma comes out, but it doesn't recover completely, it can swell and get bigger every time. It is a
drainage system so that the plasma doesn’t accumulate in certain parts of the body. Recovers excess
fluid to return it to the circulatory system. It hasn’t arteries, only closed (blind) capillaries. It is half
of the circulatory system. In this way, it doesn’t accumulate in the tissues.
For this reason, older people or people who do not exercise much have more fluid retention because
they move less. White blood cells are found in greater numbers in the lymphatic system. All lymph
is re-entered into the system. Fat collects in the lymphatic system.

Lymph capillaries
Vert thin vessels closed at one end, found in all tissues.
Function: They collect excess interstitial fluid.

Lymphatic vessels
Larger vessels with valves that prevent the lymph from flowing backwards.
Function: They return excess lymph to the circulatory system.

Lymph nodes (glands)

Small bean-shaped organs. They are located along major arteries and veins, but are most abundant
around the ears and in the neck and armpits.
Function: They contain defence cells that locate and fight microorganisms that could cause
infection, the nodes become larger.

Lymph
Consists of interstitial fluid that flows into the lymphatic vessels.
- Lymph flows through the body in only one direction.
- It moves primarily by contractions of the lymphatic vessels and skeletal muscles, by
respiratory movements of the thorax and, in some cases, by gravity.
Blood is a thick red liquid that flows inside the blood vessels.

Blood is made up of:

- Blood plasma: A yellowish liquid that makes up 55% of blood. It consists of water and
dissolved substances. These substances include proteins involved in functions like clotting,
transporting substances or defence through in immune system.

- Blood cells: Red blood cells, white blood cells and platelets make up the remaining 45% of
blood. They are formed in the red bone marrow located inside some bones.

White blood cells (leucocytes) Red blood cells (erythrocytes) Platelets (thrombocytes)

Size: largest blood cell. Most abundant. Cell fragments.

Nucleus: present. Nucleus: absent, therefore, they Nucleus: absent.
Types: neutrophils, basophils, cannot be reproduced. We have Function: help blood to
eosinophils, lymphocytes, cells that produce red blood cells, clot by forming a plug to
monocytes. but they do not reproduce by close small breaks in the
Function: protect the body themselves. blood vessels.
against infection and foreign Shape: biconcave disc. Lifespan: 8–12 days.
substances. Essential component: Count: 150 000-450 000
Count: 5000-10 000 per mm3 of haemoglobin, responsible for its platelets per mm3 of blood.
blood. red colour. They cannot be
Function: transport oxygen; pick reproduced.
up carbon dioxide for elimination.
Lifespan: about four months.
Count: 4,5-5,5 million red blood
cells per mm3 of blood.
When an infectious virus comes, the cells reproduce very quickly and attack it, because they have
seen this virus before (vaccine). The white balloons rise and indicate that we are fighting an illness.
Blood has four main functions:

Transport of solid and gaseous substances

- Blood carries nutrients from the digestive tract and oxygen from the respiratory system to
the tissues.
- It collects waste and carbon dioxide from the tissues for elimination.
Defence
Blood contains white blood cells and certain proteins responsible for the defence and protection of
the body.

Control of bleeding
Platelets and plasma proteins form a plug to close breaks in blood vessels.

Mantain body temperature

Blood mantains body temperature at about 37OC so that the metabolic functions properly.
In addition to blood, the blood circulatory system includes the blood vessels and the heart.
Blood vessels are a network of tubes. There are three types: arteries, veins and capillaries.

It is a closed system because the blood does not leave the blood vessels. The sphygmomanometer
measures your blood pressure. When a person has low blood pressure, they feel dizzy because not
enough blood is getting to them. Only large systems have a closed and developed system (dinosaurs,
birds...) Pressure is very important, because you can die from decompression. Blood must always
return to the heart.
Arteries
They carry blood away from the heart.
Size: larger near the heart; thinner and smaller arterioles farther from the heart.
Arterial walls: thick and elastic.

Arteries are the blood vessels that carry blood throughout the body, they are quite large and are at
the exit from the heart. They withstand a lot of pressure, they have elastic and flexible walls to hold
it properly, they are located inside and are not exposed (usually) in the armpit, in the leg and in the
neck (jugular), even in the arm they are exposed and have more danger. They branch out and
become smaller and will be called arterioles.

Veins
They carry blood from the organs to the heart.
Size: venules (thin veins) farther from the heart; larger and thinker veins closer to the heart.
Veins walls: valves prevent from flowing backwards.
The veins have valves that only allow blood to pass in one direction, if the valves fail the circulation
will not work well. They carry little pressure and the walls of the veins are thinner.

Capillaries
Capillaries are very thin ducts, they are semi-permeable membranes. Connects arteries and veins.
Facilitates the exchange of gases, nutrients and waste. The walls of the capillaries are a layer of flat
cells, the capillary endothelium.
The heart is a muscular organ about the size of a fist.
- It is situated between the lungs, just to the left of the sternum.
- Heart walls consists of cardiac muscle called myocardium that pumps the blood.
- The heart is made up of four chambers: two atria at the top and two ventricles below them.
- The right and the left sides of the heart are separate by a partition.
- However, the chambers on the same side are connected:
The tricuspid valve connects the right atrium and the right ventricle.
The mitral valve connects the left atrium and the left ventricle.
Both valves open to let blood and close to prevent it from flowing backwards.

Blood always flows toward the heart through the veins and away from the heart through arteries.
Although oxygenated blood and deoxygenated blood both pass through the heart, due to the
structure of the heart they never mix.
1. Deoxygenated blood enters the right atrium through the superior vena cava and the inferior
vena cava. Then it passes to the right ventricle.
2. Deoxygenated blood leaves the right ventricle and enters the lungs through the pulmonary
artery. This artery has two branches, one for each lung. The pulmonary semilunar valve
prevents blood from flowing backwards.
3. Oxygenated blood leaves the lungs through the pulmonary veins, two from each lung, and
enters the left atrium.
4. Oxygenated blood leaves the left ventricle through the aorta. The aortic semilunar valve
prevents blood from flowing backwards. From the aorta, blood flows to all the organs.
5. The coronary arteries supply blood to the muscle tissue of the heart.

The cardiac cycle

The cardiac cycle consists of one complete sequence of contraction and relaxation of the heart.
This cycle occurs during each heartbeat.
Coordinated rhythmic contraction (systole) and relaxation (diastole) involve all four chambers of
the heart.
It produces sounds. They are caused by the closing of the four heart valves.
The three phases of the cardiac cycle in sequence are:
1. Atrial systole.
2. Ventricular systole.
3. Diastole.

Atrial systole
- Both atria contract, pushing blood through the tricuspid and mitral valves into the
ventricles.
- Both ventricles fill with blood.
Ventricular systole
- Both ventricles contract.
- The pulmonary and aortic valves open, and blood is pushed through the pulmonary artery
and aorta.
- The mitral and tricuspid valves close, preventing blood from flowing backwards into the
atria.
Diastole
- The atria and ventricles relax.
- The aortic and pulmonary valve are closed.
- The atria fill with blood.
 - The atrioventricular valves open.
- The ventricles fill with blood.

Page 59 exercise 2
Imagine you are a drop of blood in the left atrium. Describe your journey through the heart, to the
lungs, back through the heart and then to the body. Underline the words in red or blue ink to
indicate if you are oxygenated or deoxygenated.
I leave the left ventricle through the aorta artery. I get smaller, because as I get further away, this
artery branches into smaller and smaller ducts until it becomes very fine blood capillaries. There I
pass through the cells of the tissues and leave nutrients and oxygen in them, I receive carbon dioxide
and other wastes. I know my way to widen the right auric of the heart. And of course, I arrived
without oxygen. You will need to go around the lungs to get it. I go to the right ventricle and leave
the heart, but this time I do it through the pulmonary arteries. When I reach the lungs, I release
the carbon dioxide and fill with oxygen to return to the left atrium of the heart through the
pulmonary veins and thus start a new journey.

Oxygenated: colour blue

Deoxygenated: colour red

Correction. Left atrium - Mitral valve - Left ventricle - Aortic semilunar valve-Aorta - Teixit - Cava
vein - Right Atrium - Tricuspid valve - - Right ventricle - Aortic semilunar valve-Pulmonary artery
- The lungs - Pulmonary veins - Left atrium.

Page 59 exercise 3
Explain the term cardiac cycle. Use the words: systole and diastole.
The cardiac cycle consists of a complete sequence of coordinated rhythmic contraction, called
systole, and relaxation, called diastole. This cycle occurs during each heartbeat.

Page 59 exercise 4
This drawing of a heart is not correct. What consequences would these malformations have in real
life? Make a new drawing and label the parts. Find information on the Internet.
The drawing is wrong because the right pulmonary veins enter the right atrium, this causes
oxygenated and deoxygenated blood to mix and you die.
The heart has a double circulation system that keeps oxygenated blood (arterial blood) and
deoxygenated blood (venous blood) separate as they both pass through the heart:

The pulmonary circuit pumps blood to the heart and the lungs.
The systemic circuit links the heart and the rest of the body.

The pulmonary circuit

It begins in the right ventricle where deoxygenated blood is pumps through the pulmonary artery
to each lung. The artery branches, finally becoming a network of capillaries. The capillaries carry
deoxygenated blood to the alveoli where gas exchange occurs.
After gas exchange, oxygenated blood travels through the venous capillaries, the venules and finally
the pulmonary veins to the left atrium.

The systemic circuit

It begins in the left ventricle. From there, oxygenated blood is pumped through the aorta to the
upper and lower body. It travels through capillaries to reach the cells.
There, during cellular metabolism, nutrients and oxygen are collected while carbon dioxide and
waste are removed.
Afterwards, oxygenated blood travels through the venous capillaries, venules and finally the vena
cava to the right atrium.

Cardiovascular diseases are those that affect the circulatory system: the blood vessels or the heart.
They are very common.

Arteriosclerosis
Cause: one plaque that deposits cholesterol, fat and other substances.
Consequence:
- The walls of the arteries become hard and thick, losing elasticity.
- As the plaque increases, the diameter of the arteries decreases, which affects the blood flow.
- Pieces of plaque can break off from the wall of a blood vessel and obstruct blood flow,
resulting in an embolism.

Hypertension (high blood pressure)

Cause: smoking, alcohol, obesity and lack of exercise. In many cases, the cause of hypertension is
unknown.
Consequence:
- It can damage the arteries and force the heart to work harder.
- It can affect the heart, eyes, brain and kidneys.
- People with hypertension have high blood pressure when they are at rest.

Blood pressure
It is the force of blood pushing against the walls of arteries.
Myocardial infarction (heart attack)
Blood supply to the heart is suddenly blocked. This prevents blood and oxygen from reaching the
heart muscle, causing a heart attack.

Anaemia
A low level of haemoglobin or low number of red cells.
Haemoglobin: A protein in red blood cells that carries oxygen.
So, if the level is below normal, tissues may not receive enough oxygen.

Iron deficiency anaemia

Causes: Inadequate diet, the inability of the digestive system to absorption from food, or blood loss
from excessive bleeding.
Leukaemia
- A cancer that affects the blood and bone marrow.
- Numerous abnormal white cells are produced that cannot fight infection.
- The best treatment is a bone marrow transplant.

Haemophilia
A hereditary disease that causes blood to clot more slowly or not at all.

Interpret a blood test

Disease 1: Risk of thrombosis. Because his platelet count is out of range, he has a lot of them.
Disease 2: Leukaemia. The amount of leukocytes (white blood cells) is very high.
Disease 3: Anaemia. Few red blood cells and low haemoglobin.
Disease 4: Lives at altitude and makes more red blood cells or doping.
The circulatory system works in close relationship with all the organs of the body. For this reason,
it plays a vital part in maintaining a healthy body.

Do moderate exercise every day

Aerobic exercise benefits the heart and circulation; it also keeps the body fit. In fact, exercise helps
prevent most cardiovascular diseases. When we exercise, we sweat to maintain regular homeostasis.

Drink at least two litres of water every day

Water helps dilute and eliminate waste from the body.
Do not smoke.
Smoking increases blood pressure and stress on the heart. It is also a risk factor for arteriosclerosis.

Avoid high-fat diets

Excessive accumulation of body fat can lead to obesity, arteriosclerosis and cardiovascular diseases.
Excess body weigh increases the risk of heart attacks.

Lead a calm but active life

Avoid continuous stressful situations. Stress can lead to heart attacks.
Eat a low salt diet
Excessive salt in the diet can lead to high blood pressure.
Human cells produce waste products as a result of cellular metabolism. If this waste products
accumulates, it can be harmful.
Waste is released into the blood so that the blood can carry it to the organs responsible for
elimination.
Excretion
It is the process by which the waste products from cells are eliminated from the blood.

Organs involved in excretion

ORGAN WASTE PRODUCTS

Kidneys They eliminate toxic substances resulting from

cell metabolism through the urine.

Lungs They expel carbon dioxide from cellular

respiration.

Liver It produces a liquid called bile that helps to

eliminate waste from the digestion through
faeces.

Sweat glands Exocrine glands of the skin are responsible for

sweat excretion. Sweat is a liquid that is very
similar to urine but more diluted.
The urinary system
Consists of:
- Kidneys: two organs located along the posterior wall of the abdominal cavity.
- A renal artery: carries blood with waste to each kidney.
- A renal vein: carries the filtered blood away from the kidney.
Waste products and water become urine.
- Urinary tract
- Ureters: two tubes that connect the kidneys and the bladder.
- The bladder: a muscular elastic bag where urine is collected.
- The urethra: carries urine from the bladder outside the body during urination.

The kidneys
Each kidney has the following parts and structures:
- Renal cortex: The outer part.
- Renal medulla: The inner part that contains tissue, called renal pyramids.
- Renal pelvis: This cavity collects urine and connects to the ureters.

Nephrons and the formation of urine

Nephrons are the basic functional units of the kidneys. Each kidney has about one million.
Urine, a liquid made up of water, salts and waste such as urea and uric acid is formed in the
nephrons. This is done using filtration and reabsorption. About 1.5 litres of urine are produced
every day.
1. Glomerulus: A mass of tiny capillaries through which blood and waste products pass.
2. Bowman’s capsule: A sac surrounding the glomerulus. Most small molecules like water
and salts are filtered into Bowman’s capsule from the capillaries.
3. Proximal convoluted tubule (PCT): Useful substances such as glucose, amino acids,
ions, vitamins and filtered water are reabsorbed here.
4. Collecting duct: This duct collects urine and channels it into the renal pelvis. From there,
urine is transported into the ureter.
5. Loop of Henle: It reabsorbs ions and some water.
6. Distral convoluted tubule (DCT): Ions are reabsorbed here.
Diseases and disorders associated with the urinary system include:

Cystitis
Inflammation of the bladder wall or urinary tract, usually caused by bacterial infection.
Consequence:
- Pain, burning sensation when urinating, frequent urination and difficulty urination.

Pyelonephritis
Acute inflammation that affects the renal cortex, medulla and renal pelvis; usually due to bacterial
infection.

Renal colic
Cause: Kidney stones - Are mineral deposits made up of waste from the blood that collects in the
renal pelvis.
It is produces when they pass through narrow tubes like the ureter.
Kidney disease (renal failure)

Acute: The kidneys suddenly stop filtering waste products from the blood; urine flow is low.
Treatment enables the kidneys to recover.

Chronic
A slow, gradual loss of kidney function. If too many waste products accumulate in the blood,
nephrons are damage and destroyed.
A healthy lifestyle is the best way to prevent diseases of the excretory system.
Some healthy habits are:

Drink a lot of liquids.

Between one and two litres of water a day. Water hydrates the body, helps the kidneys to eliminate
waste and reduces the risk of kidney stones.

Eat a balanced diet.

Diet is linked to the formation of kidney stones. Limiting the intake of foods with calcium oxalate
such as tea and chocolate may prevent the formation of calcium stones. Too much animal protein
increases the level of uric acid and can lead to kidney stones. Drinking water and eating fibre helps
to prevent kidney stones.

Limit salt in your diet.

Eating less salt may prevent hypertension.

Avoid self-medication.
Many medicines or drugs are excreted in the urine. Use medicines under professional supervision to
prevent damage to the kidney function.

Maintain good hygiene of the external genital area.

Washing is especially important for women because bacteria can reach the bladder through the
urethra, causing infection. Empty the bladder completely during urination to prevent urinary tract
infections.

LAB PRACTICE: HEART’S DISSECTION

We will use the lambs’s heart we saved from the previous practice, the lung dissection, to
study the anatomy of the heart. It is interesting to study the lungs together with the heart, as
we can observe the relationship between the organs and the blood vessels.

Materials (list the material we used)

​ Lamb heart
​ Scalpel
​ Scissors
​ Tray
​ Two gloves
​ Pliers
​
Procedure

Identify the right and left sides of the heart.

Locate the coronary arteries and veins that are on the surface of the heart.
Identify the following vessels: AORTA; PULMONARY ARTERY; PULMONARY VEIN;
SUPERIOR VENA CAVA; INFERIOR VENA CAVA.
Place a pencil in the opening vessels.
Locate the aorta, which leads away from the left ventricle.

DISSECTION
OPENING THE RIGHT SIDE:
Insert a blade of the scissors (or scalpel) into the superior vena cava and cut downward
through the atrial wall.
Open the chamber, locate the tricuspid valve and examine it.
Continue cutting downward through the tricuspid valve and the right ventricular wall until
you reach the apex of the heart.
Use the scissors to cut upwards through the wall of the right ventricle.

OPENING THE LEFT SIDE:

Insert the blade of the scissors through the wall of the left atrium and cut downward to the
apex of the heart.
Open the left atrium and locate the four openings of the pulmonary veins.
Examine the left ventricle and the mitral valve.

QUESTIONS
How many chambers are found in the mammal’s heart?
There are four chambers in the mammal's heart.
Which chambers are the pumping chambers of the heart?
The pumping chambers of the heart are the two ventricles, both the left and the right.
Which chambers are the receiving chambers of the heart?
The receiving chambers of the heart are the arteries, the left and the right.
Describe the action of the tricuspid valve when the ventricle is full.
The function of the tricuspid valve is to allow blood circulating through the body to reach the
right ventricle, it contracts to send blood to the lungs and this valve will prevent blood from
flowing back into the right atrium.
What is the purpose of heart valves?
The purpose of the heart valves is to prevent the backflow of blood. These valves are located
at either end of the two ventricles and act as one-way blood inlets on one side of one ventricle
and one-way blood outlets on the other side of the other ventricle.

Vessels that carry blood away from the heart are called veins while arteries carry blood
toward the heart.
Which artery is the largest and why?
The largest artery is the aorta and it is so because it is where all the other blood vessels
originate from and carries this oxygen-rich blood from the left ventricle to the rest of the
body.

PRÀCTICA 8: EL SISTEMA CIRCULATORI

1. Per quantes capes està format el cor?

El cor està format per tres capes.

2. Com s’anomenen?

Les capes del cor s’anomenen pericardi, miocardi i endocardi.

3. Quina funció té cada capa?

El pericardi és la membrana que envolta el cor i el protegeix. El miocardi és un teixit

muscular que gràcies a ell, el cor pot bategar i bombar sang. Per últim, l'endocardi
és una membrana que cobreix i protegeix l’interior del cor.

4. Quantes càmeres té el cor?

El cor té quatre càmeres.

5. Com s’anomenen aquestes càmeres?

Aquestes càmeres s’anomenen ventricles i aurícules, en tenim dues de cada.

6. Quin és el circuit menor? Quina funció fa?

El circuit menor és el que està compost per l’aurícula dreta i el ventricle esquerre.
Aquest té la funció de portar la sang fins als pulmons perquè la tornin oxigenada.

7. Quin és el circuit major? Quina funció fa?

El circuit major és el que parteix de l’artèria aorta, i la seva funció consisteix a fer
que a partir d’aquesta, la sang oxigenada surti del ventricle esquerre i circuli per tot
el cos, tornant a entrar al cor per l’aurícula dreta.

8. Com s’anomenen els moviments de contracció i relaxació del cor?

Els moviments de contracció i relaxació del cor s’anomenen sístole i diàstole.

9. Què és necessari perquè el cor bategui?

Perquè el cor bategui és necessari que hi hagi un impuls elèctric produït per un
sistema de cèl·lules que reben el nom de nòdul sinusal i es troben a l’aurícula dreta.
Aquest impuls es transmetrà per uns cables que es connectaran a totes les cavitats
per a generar la contracció que bomba la sang. I el recorregut tornarà a començar
quan rebi la sang que els pulmons s’encarreguen d’oxigenar.

10. Quants litres de sang es bombegen cada minut?

Cada minut es bomben cinc litres de sang.

11. Quin percentatge de la sang es plasma?

El 55% de la sang es plasma.

12. Què conté aquest plasma?

Aquest plasma conté proteïnes, nutrients i substàncies de rebuig recollides de les

cèl·lules.

13. Quin percentatge de la sang són cèl·lules?

El 45% de la sang són cèl·lules.

14. Com s’anomenen aquestes cèl·lules, I quina funció tenen?

Aquestes cèl·lules s’anomenen glòbuls vermells, glòbuls blancs i plaquetes. Els

glòbuls vermells tenen la funció de transportar l’oxigen i recollir el diòxid de carboni
que s’ha generat a les diferents cèl·lules i portar-lo de tornada als pulmons, on
s’eliminarà. Els glòbuls blancs s’encarreguen de la resposta immunitària de
l’organisme, és a dir, són els que eliminen els agents infecciosos i les cèl·lules
infectades. Per últim, les plaquetes que intervenen a la coagulació de la sang, quan
es trenca un vas sanguini, rodegen la ferida per disminuir la dimensió, i així, amb
més factors de coagulació, eviten el sagnat.

15. Com es diu l’artèria més gran del cor?

L’artèria més gran del cor és l'aorta.

16. Quina funció fan els capil·lars?

Els capil·lars al circuit major fan la funció de l’intercanvi de substàncies entre la sang
i les cèl·lules del cos, així, la sang aporta oxigen i nutrients perquè les cèl·lules
continuïn vives i recull substàncies metabòliques i diòxid de carboni.

17. Per què és dolent el colesterol?

Es diu que les venes són com un sistema de vies i carreteres en les quals a
vegades, en alguns carrers o avingudes del cos es poden produir embotellaments i
accidents a causa del colesterol que és el principal responsable d’aquests incidents.
El colesterol s’acumula i obstrueix les artèries i el trànsit de la sang es complica.
18. Què és un infart?

Un infart es produeix quan les artèries es taponen per complet i la sang no

aconsegueix arribar al destí amb l’oxigen i els nutrients. Existeixen tres tipus
diferents d’infarts: si l'artèria danyada és una de les que irriga el cor s’anomena infart
de miocardi, si irriga al ronyó rebrà el nom d’infart renal i si és una artèria de les que
va al cervell serà un accident cervell vascular o ACV.

19. Quin òrgan és l’encarregat d’alimentar als embrions quan estan al ventre de la
mare?

La placenta és l’òrgan encarregat d’alimentar als embrions quan estan al ventre de

la mare.

20. Com s’anomena el sistema de circulació que alimenta aquests embrions?

El sistema de circulació que alimenta aquests embrions rep el nom de circulació

fetal.