CVS Block..anatomy Word 2022
CVS Block..anatomy Word 2022
CVS Block..anatomy Word 2022
HEART
Mediastinum
Superior mediastinum
Boundaries:
- Anterior: Manubrium sterni.
- Posterior: upper 4 thoracic vertebrae
- Two sides: mediastinal pleurae.
- Superior: thoracic inlet.
- Inferior: imaginary line & inferior mediastinum.
Contents of the superior mediastinum
1- Retrosternal layer: contain thymus or its rudiment;
2- Venous layer:
- right and left brachiocephalic V. - superior vena cava.
3- Arterial layer:
- Arch of aorta and its 3 branches;
- RT and LT phrenic and vagus n.
4- Tubal layer
- Trachea.
- Esophagus.
- Left recurrent laryngeal nerve
- Thoracic duct.
Anterior mediastinum
Boundaries:
- Anterior: body of the sternum. - Posterior: middle mediastinum.
- Two sides: mediastinal pleurae.
- Superior: imaginary line & superior med. - Inferior: the diaphragm
Contents:
1- Sternopericardial lig.(sup. & inf.)
2- remnants of thymus gland.
3- anterior mediastinal lymph nodes 4- fat.
Middle mediastinum
Boundaries:
- Anterior: anterior mediastinum..
- Posterior: posterior mediastinum.
- Two sides: mediastinal pleurae.
- Superior: imaginary line & superior mediast.
- Inferior: the diaphragm
Contents
1- heart 2- pericardium(fibrous and serous).
3- great vessels of heart(aorta, pulmonary, SVC and IVC).
4- phrenic nerves, pericardiacophrenic vessels
5- lymph nodes. 6- fat.
Posterior mediastinum
Boundaries:
- Anterior: middle mediastinum.
- Posterior: lower 8 thoracic vertebrae
- Two sides: mediastinal pleurae. - Inferior: the diaphragm
- Superior: imaginary line & superior mediastinum.
Contents:
① principal bronchi. ② thoracic part of
esophagus.
③ descending thoracic aorta. ④ thoracic duct.
⑤ azygos and hemiazygos V. ⑥ vagus nerves.
⑦ sympathetic trunk and lymph nodes.
Pericardium
- It is a double-walled sac around the heart composed of:
- A superficial fibrous pericardium
- A deep two-layer serous pericardium formed of:
1- Parietal pericardium (outer) lines the internal surface of the fibrous
pericardium
2- Visceral pericardium (inner) or epicardium lines the surface of the
heart
3- Pericardial cavity: fluid-filled cavity between visceral and parietal layers.
Fibrous pericardium: conical in shape; its apex directed upwards and
base directed downwards.
- Its apex fused with the coats of ascending aorta, pulmonary trunk,
pulmonary veins and SVC.
- Its base fused with central tendon of diaphragm.
Relations:
- Anteriory:
= sternopericardial lig. = ant. Chest wall. = lungs and pleurae
- Posteriory: descending aorta and oesophagus.
- On each side: phrenic n., pericardiacophrenic A, lungs and pleurae.
Serous pericardium: formed of 2 layers:
- Parietal (outer layer): lines the internal surface of the fibrous pericardium.
- Visceral (inner layer): or epicardium lines the surface of the heart
- The 2 layers are separated by the fluid-filled pericardial cavity filled
with pericardial fluid
Functions of serous pericardium:
- Protects and anchors the heart
- Prevents overfilling of the heart with blood
- Allows for the heart to work in a relatively friction-free environment.
Sinuses of serous pericardium
1- Transverse sinus:
It is a transverse passage inside the pericardial cavity. Its boundaries:
- Anteriory: pulmonary trunk and ascending aorta.
- Posteriory: SVC, RT and LT atria.
- Above: RT pulmonary artery.
- Below: the 2 atria.
2- Oblique sinus:
visceral pericardium ascends on diaphragmatic surface of the heart. It is
then reflected downwards to form parietal layer of serous pericardium.
This sinus lies behind the LT atrium and has the following boundaries:
- Anteriory: back of LT atrium.
- Posteriory: fibrous pericardium
- On LT side: 2 LT pulmonary veins.
- On RT side: 2 RT pulmonary veins.
Blood supply of the pericardium
- Fibrous and parietal serous: by pericardiaco-phrenic and descending
thoracic aorta.
- Visceral: as the heart(coronary vessels).
Nerve supply of the pericardium :
- Fibrous and parietal serous: as thoracic wall(intercostal nerves)
- Visceral: autonomic NS(sympathetic and parasympathetic).
THE HEART
Site: located directly behind sternum, in the middle mediastinum, with its
⅔ LT and its ⅓ RT to midline.
Axis: downward, forward and to the LT(from base to apex).
Size: approximate size of clenched fist
The heart wall: formed of;
- Epicardium: outer layer
- Myocardium: middle layer
- Endocardium: inner layer
Shape: the heart is cone shaped, has apex,
base , 2 surfaces and 4 borders:
Apex -Formed by left ventricle.
-leftmost, lowermost, part of heart.
- Lies at LT 5th intercostal space 9 cm from midline.
Base - Formed by left atrium mainly.
- related posteriory to posterior mediastinum contents
(descending aorta, esophagus, azygos vein, thoracic duct).
2 surfaces - Anterior - Behind sternum and attached ribs.
(sterno-costal) - Formed by LT vent (⅓), RT vent (⅔)
- Inferior - Lies on the diaphragm.
(diaphragmatic) - Formed by RT vent(⅓) ,LT vent(⅔)
4 borders Right border Formed by right atrium.
Left border. Formed by left ventricle mainly.
Lower border by right ventricle + apex of heart.
Upper border Formed by both atria
Internal features of the Heart(Chambers of the
heart)
Rt atrium Lt atrium
Position: - lies anterior and Rt to Lt atrium - lies behind and to the Lt of Rt
- forms Rt border of the heart. atrium
- share in sternocostal surface of - forms the base of the heart.
the heart.
Its Overlaps the Rt anterior aspect Overlaps the Lt anterior aspect
auricle: of root of pulmonary tract. of root of pulmonary tract.
Its cavity: Divided by crista terminalis into: Its cavity is generally smooth
1- posterior smooth part. except its auricle which show
2- anterior rough part: due to few musculi pectinati.
musculi pectinati.
Interatrial Show fossa ovalis and annulus Showa faint impression
septum: ovalis. corresponding to fossa ovalis
Veins It receive deoxygenated blood It receive oxygenated blood
draining from all the body except lungs returning from lungs through the
into: through: 2 Rt and 2 Lt pulmonary veins
1- SVC. 2- IVC. and also vena cordis minimi
3- Coronary sinus
4- anterior cardiac veins.
5- vena cordis minimi
Exit of Through tricuspid valve which Through mitral valve which has
blood has 3 cusps, and leads to Rt 2 cusps, and leads to Lt
from it: ventricle. ventricle.
Heart Valves
1- Atrioventricular (AV) Valves
- Right AV valve (tricuspid): between RA and RV
- Left AV valve (bicuspid or mitral): between LA
and LV
2- Semilunar Valves
- Pulmonary valve: between RV and pulmonary trunk
- Aortic valve: between LV and aorta.
2- Ventricles of the heart:
Rt ventricle Lt ventricle
Position: - lies anterior and Rt to Lt - lies posterior and Lt to Rt
ventricle ventricle
- forms inferior border of the - forms apex and left border
heart. of heart.
- Forms Lt ⅔of sternocostal - Forms Lt ⅓of sternocostal
surface of the heart. surface of the heart.
- Forms Lt ⅓ of - Forms Lt ⅔ of
diaphragmatic surface of diaphragmatic surface of
heart. heart.
Cross Crescent Circular
section:
Its cavity: Divided into: Divided into:
1- outflow smooth part: called 1- outflow smooth part:
infundibulum lies below called aortic vestibule lies
pulmonary orifice. below the aortic orifice.
2- inflow rough part: below 2- inflow rough part: below
the opening of tricuspid opening of mitral valve.
valve. This roughness due to: This roughness due to:
A- trabeculi carini: few and A- trabeculi carini: fine and
coarse numerous
B- papillary muscles(3 , B- papillary muscles(2 ,
anterior, posterior and septal). anterior and posterior).
C- the moderator band. C- no moderator band.
Wall 9 mm 27mm
thickness
Openings: - It receive non oxygenated - It receive oxygenated blood
blood from Rt atrium through from Lt atrium through the
the tricuspid valve(has 3 mitral valve(has 2 cusps,
cusps, anterior, posterior and anterior and posterior)
septal) - It pump the blood to body
- It pump the blood to lung through aortic valve(has 3
through pulmonary valve(has semilunar cusps, 2 post and 1
3 semilunar cusps, 1 post and ant.)
2 ant.)
Sinous venousus
At early stage: It formed of body and 2 horns, each horn of the sinus
venosus receives 3 types of veins:
1- Common cardinal(CCV): from the fetal body, it is formed by union of
2 veins:
- anterior cardinal(AC): receive blood from upper ½ of the fetal body
- posterior cardinal(PC): receive blood from lower ½ of the fetal body
2.Vitelline(VV): from the yolk sac.
3.Umbilical(UV): from the placenta.
At late stage:
- an anastomotic channel is formed
between the 2anterior cardinal veins →
shift the blood from left to right side→ enlargement of right horn
Fate:
# RT horn→ smooth posterior part of RT atrium.
# LH + Body → coronary sinus.
# Lt common cardinal vein → oblique vein of Lt atrium.
Partitioning of Primordial Heart: through partitioning of:
1- Atrioventricular canal.
2- Common atrium.
3- Common ventricle.
4- Bulbus cordis
5- Truncus arteriosus
Partitioning of the atrioventricular canal(AV canal):
- Two endocardial cushions are formed on the dorsal and ventral walls of
the AV canal.
- The AV endocardial cushions
approach each other and fuse to
form the septum intermedium→
Dividing the AV canal into right
& left canals.
- These canals separate primordial
atrium from primordial ventricle.
Partition of the common atrium (interatrial septum).
1- Septum Primum
- It is sickle- shaped septum that grows
from the roof of the common atrium
towards the fusing endocardial
cushions (septum intermedium)
- The two ends of the septum primum
reach to the growing endocardial
cushions before its central part, So the septum primum bounds a foramen
called ostium primum. It serves as a shunt, enabling the oxygenated blood
to pass from right to left atrium.
- ostium primum become smaller and disappears as the septum primum fuses
completely with endocardial cushions to form the interatrial septum.
- The upper part of septum primum that is attached to the roof of the
common atrium shows gradual resorption forming an opening called ostium
secondum.
2- Septum secundum.
- Another septum descends on the right side of the septum primum.
- overlap between septum primum and secundum forms an incomplete
partition between the two atria leave an oval foramen forms (foramen ovale)
Fate of foramen Ovale
- At birth when the lung circulation begins→ the pressure in the left
atrium increases and exceeds that of the right atrium →So the two septae
oppose each other→obliterate the foramen and its site is represented by
the Fossa Ovalis.
- The septum primum forms the floor of the fossa ovalis.
- The septum secondum forms the margin of the fossa ovalis which also
called the limbus (anulus) ovalis.
Sources of the 2 atria
Rt Atrium Lt Atrium
- Smooth posterior part: derived from the - Rough part: derived
right horn of the sinus venosus from the common
- Rough anterior part: derived from the primordial atrium.
primordial common atrium. - The smooth part:
NB: These two parts are demarcated by the derived from the absorbed
crista terminalis internally and sulcus Pulmonary Veins.
terminalis externally.
RT coronary artery
Branches:
LT coronary artery
Course: larger then RT and supplies large parts of the heart. This artery
lies between the pulmonary trunk and the left atrial auricle, emerging into
the AV groove, in which it turns left. Then it divides into two main
branches.
Branches:
3. Coronary sinus.
Coronary sinus
Site: wide venous sinus, 2-3 cm long, lying in the posterior AV sulcus
between base and diaphragmatic surface of heart.
Termination: it opens into the right atrium between the opening of the
inferior vena cava and the tricuspid orifice.
Tributaries: are the great, small and middle cardiac veins and the
oblique vein of the left atrium.
3- Middle cardiac vein: begins at the cardiac apex, and runs back in the
posterior IV groove to end in the coronary sinus at its middle.
Arch of Aorta
Beginning: continuation of ascending aorta at RT end of sternal angle.
Course: curves upward, to the left and posteriorly, then downward, arching
over left principal bronchus and pulmonary trunk
End: at lower border of T4, to become descending aorta.
Relations of aortic arch
- Anteriorly and to the left: pleura, lung, phrenic n., pericardiacophrenic
vessels and vagus n.
- Posteriorly and to the right: trachea, esophagus, left recurrent n.,
thoracic duct, deep cardiac plexus
- Superiorly: its three branches, left
brachiocephalic v. and thymus
- Inferiorly: pulmonary a., ligamentum
arteriosum, left recurrent n., left principal
bronchus and superficial cardiac plexus
Veins of thorax
- Brachiocephalic veins
- Begin by union of internal jugular and subclavian veins posterior to the
sternoclavicular joint
- Rt and LT brachiocephalic unite to
form SVC.
Superior vena cava
Beginning: by union of right and left
brachiocephalic veins behind the right
1st sternocostal junction.
End: right atrium at lever of lower border of 3rd right sternocostal joint
- it collects blood from veins of upper half of body
Tributaries: azygos vein at level of sternal angle(2nd costal).
Development of Aorta
– Primitive embryonic Aortae:
• Two straight vessels on each side of the midline are present→after
folding, the two arteries are bend to form:
- Dorsal aortae: dorsal to the gut.
- Ventral aortae: ventral to the gut.
- Connecting segment: on each side of the bucco-pharyngeal membrane.
Aortic sac: dilated arterial channel formed by the union of the 2 ventral
aortae, ventral to the pharynx. It continuous with the truncus arteriosus,
caudally. It has a stem and 2 horns(RT and LT). Its branches are:
– 2 ventral aortae.
– 6 pairs of aortic arches around the pharyngeal arches
• Fate of aortic sac:
– The stem & the left horn: involved into the adult aortic arch.
– Right horn: gives off the proximal part of the brachiocephalic artery.
Aortic arches:
• 6 pairs of arteries between the aortic sac
& 2 dorsal aortae around the
pharyngeal arches.
• Derivatives(fate):
– 1st arch: degenerated, may be involved
in maxillary artery.
– 2nd arch: degenerated, may be involved
in stapedial artery.
– 3rd arch: forms the common carotid arteries.
– 4th arch: on the left side, it is involved in formation of the adult aortic
arch. On the right side, it is involved in the formation of the RT subclavian
artery.
– 5th arch: degenerated.
– 6th arch: forms the right & left pulmonary arteries and ductus
arteriosus.
Dorsal aorta:
• It develops from the fusion of 2 dorsal aortae from 4th thoracic down
to 4th lumbar somite.
• Fate:
– Cranial to the 3rd aortic arch: it
forms the distal part of internal carotid
artery (ICA).
– Between 3rd & 4th arches:
degenerated.
– Between 4th arch down to 7th
cervical inter-segmental artery:
involved in the right subclavian artery or in the adult aortic arch on the
left side.
– below 7th cervical inter-segmental artery: degenerated on the right side or
involved in descending thoracic aorta on the left side
• the adult aortic arch develops from:
• Proximal part of the arch: from the stem of the aortic sac.
• Middle part: from the left horn of the aortic sac.
• Distal part: from the left 4th arch & left dorsal aorta
down to the origin of 7th cervical inter-segmental artery (LT subclavian
artery).
– The adult descending aorta: from the left dorsal aorta, caudal to the
origin of the 7th cervical intersegmental artery, while the right dorsal aorta
degenerates.
• Aortic anomalies:
1- Coarctation of aorta: the aortic lumen is significantly narrow below
the origin of the left subclavian artery, it affects the blood supply of LL.
2- Abnormal origin of right subclavian artery: The right subclavian arise
from persistent distal part of right dorsal aorta.
3- Double aortic arch: persistent both distal part of right dorsal aorta &
right 4th aortic arch. The second component of the aortic arch passes
behind the esophagus causes difficulty in swallowing and respiration.
Development of veins
- In a 4th weeks embryo, three paired veins open into the tubular heart:
Vitelline Veins
- Pass through the septum transversum and drain into the sinus venosus
♥ Post-hepatic part: left vein disappears but right vein forms the:
Umbilical Veins
- As the liver grows, the umbilical veins loose their connection with heart
and open into the liver.
- The right vein disappears by the end of the embryonic period. The left
vein persists.
- After birth:
- The left umbilical vein obliterate to form the ligamentum teres of the liver
Cardinal veins:
• They are longitudinal veins, mesodermal in origin, symmetrical on both
side of the body& drain the body of embryo.
• They developed gradually: anterior, posterior & common cardinal veins
developed earlier than supra-cardinal & sub-cardinal veins
• Anterior cardinal veins: Present cranial to the heart level, drain head &
UL buds.
• Posterior cardinal vein: caudal to the heart level, drain trunk & LL buds.
• Common cardinal vein: two short venous channels formed by union of
anterior & posterior cardinal veins, they drain into the sinus venosus.
• Sub-cardinal vein: Present caudal to the heart level, ventro –medial to
the mesonephric ridge.
• Supra-cardinal vein: Present caudal to the heart level, dorso-lateral to
the dorsal aorta.
– Both subcardinal & supracrdinal veins gradually replace the posterior
cardinal.