ZOOLOGY LEC (FINALS)

INTEGUMENT
- The integument is this the protective outer covering of the animal body
- It includes the skin and structures associated with the skin (derivatives of the skin) such as hair, nails, scales, feathers, and
horns

FUNCTIONS OF INTEGUMENT

- Protection from mechanical & chemical injury

- Protection against invasion by microorganisms
- Regulation of body temperature
- Excretion of waste materials
- Vitamin D production
- Reception of environmental stimuli
- Locomotion/movement
- Controls movement of nutrient and gases

INVERTEBRATE INTEGUMENT

- Some singled-celled protozoa have only a plasma membrane for external covering (Amoeba)
- Other protozoa have a thick protein coat called pellicle outside the plasma membrane (Paramecium)
- Most multicellular invertebrates have a single-layered epidermis covering the body (nematodes, annelids)
- Others have added a secreted non-cellular cuticle over the epidermis (crustaceans, arachnids, insects)
- Additional protection:
Old cuticles need to be shed periodically in a process called
molting to permit growth
- Molluscs have a delicate epidermis. Protection is provided by the shell

- Cephalopods have a more complex epidermis with a cuticle, simple epidermis, layer of connective tissue, & a layer of
iridocytes – a guanine-containing cell in the skin of fish and some cephalopods, giving these animals their iridescence.

- Arthropods have a complex integument that

provides protection and skeletal support
 Single layered epidermis (hypodermis) which
secretes a complex cuticle
 Procuticle – layers of chitin and protein
 Epicuticle – moisture proofing barrier

- The arthropod cuticle may remain tough, but flexible as in

many small crustaceans and insect larvae, or it may become hardened
 Decapod crustaceans have a cuticle stiffened by calcification (deposition of calcium carbonate in the procuticle)
 In insects, hardening occurs by sclerotization where protein molecules bond together producing the insoluble
protein sclerotin

Other Examples of Invertebrate Integument:

Rotifers – cuticles are thin and elastic
Arthropods – cuticles are thick and rigid
Cnidarians – epidermis is only a few cell
 layers thick (Hydra), contains
mucous glands that secrete calcium
carbonate shells (corals)
Platyhelminthes – covering is a tegument
(functions for nutrient ingestion and for protection)
Nematodes and annelids – have an epidermis that is
one cell thick and secretes a multilayered cuticle
Echinoderms – integument consists of a thin, ciliated
epidermis & an underlying connective tissue dermis
that contains calcium carbonate

VERTEBRATE INTEGUMENT

- Vertebrate Integument includes:

 Epidermis – thin outer stratified epithelial layer, derived from ectoderm

 Dermis – thickinner layer, derived from mesoderm

- Epidermis

 The epidermis gives rise to hair, feathers, and

hooves (epidermal derivatives)
 Epidermis is stratified squamous epithelium
 Cells in the basal part undergo frequent mitosis
 As cells are displaced upward, cytoplasm is replaced
by keratin
 Keratin is a tough protein that is also light and flexible
 Reptile scales are composed of keratin
 Birds have keratin in feathers, beaks, and claws
 Mammals use keratin in hair, hooves, claws, and nails

Sweat Glands

 Different types prevent overheating of the body; secrete sweat, cerumen and milk
 Eccrine sweat glands – found in palms, soles of the feet, and forehead
 Apocrine sweat glands – found in axillary and anogenital areas
 Ceruminous glands – modified apocrine glands in external ear canal that secrete cerumen
 Mammary glands – specialized sweat glands that secrete milk

Sebaceous Glands

 Simple alveolar glands found all over the body

 Soften skin when stimulated by hormones
 Secrete an oily secretion called sebum

Skin Receptors

 Meissner’s corpuscles – touch receptors

 Pacinian corpuscles – pain receptors
 Ruffini’s corpuscle – heat receptors
 End Bulbs of Krause – cold receptors
  Merkel’s disk – texture and touch receptors

Structures associated with Skin

Hair

 Composed of keratin-filled dead cells that developed from epidermis

 The part of the hair below the surface of the skin is called the hair follicle . The hair follicle is a tube-like structure that
surrounds the root and strand of a hair. It is located in the epidermis, the top layer of the skin, and extends to the
dermis, the second layer of the skin.
 The hair shaft is the part of the hair that is visible above the skin, while the hair root is the part of the hair that is
anchored in the follicle and lies below the surface of the skin.
 The base of the hair refers to the bottom part of the hair follicle, where the hair bulb is located.

Nails

 Modification of epidermis. Flat, horny plates on dorsal surface of distal segments of the digits
 The most rapidly dividing cells within the nails can be found in the nail matrix, which is located beneath the nail plate.
The nail matrix is responsible for producing the nail plate, which is the visible part of the nail that sits on top of the
nail bed. The nail plate is made up of hard, dead cells that are produced by the matrix and consists of carbon,
hydrogen, oxygen, sulfur, and nitrogen.
 The lunula is the half-moon shaped point where the matrix and nail bed meet. It is the most visible part of the matrix
and appears white because the underlying blood vessels are not visible through the nail plate.
 The nail bed is the part of the finger underneath the nail plate, and the free edge is the part of the nail plate extending
from the finger

SKELETAL SYSTEM

- Skeleton is the hardened part of the animal body

Functions:

- Supports the body

- Framework of the body
- Protects vital organs of the body
- Blood cell formation/hematopoiesis
- Site for the attachment of muscles
- Accessory to movement
- Storage of minerals

Hydrostatic Skeletons

- In the hydrostatic skeleton of an earthworm, muscles in the body wall develop force by contracting against
incompressible coelomic fluids
- Alternate contractions of circular and longitudinal muscles of the body wall enable a worm to move forward

Rigid Skeletons

- Rigid skeletons contain some kind of rigid elements

- Provide anchor points for pairs of opposing muscles
- Provides protection & support
Exoskeleton

- found in molluscs, arthropods, some invertebrates & vertebrates

- Lobsters, crabs, molluscs

Endoskeleton

- found in echinoderms, sponges,and chordates

- echinoderms, fishes, mammals

Vertebrate Endoskeleton

- The vertebrate endoskeleton is composed of bone and cartilage (types of connective tissue)
- Bone provides support, protection, and serves as a reservoir for calcium and phosphorous

Cartilage

- Jawless fishes (eels, hagfishes) and elasmobranchs (sharks, sting rays) have cartilaginous skeletons
- Most vertebrates have bony skeletons, with some cartilaginous parts
- Cartilage is a soft, pliable tissue that resists compression and is variable in form Hyaline cartilage has a clear,
glassy appearance with chondrocytes surrounded by a matrix
- No blood vessels
- Cartilage is often found at articulating surfaces of many bone joints, larynx, trachea, vertebral column, nose,
pinnae, and Eustachian tube.

Bone

- Bone is highly vascular living tissue that contains significant deposits of inorganic calcium salts
- Endochondral (replacement) bone develops from another form of connective tissue – usually cartilage
- Intramembranous bone develops directly from sheets of embryonic cells, face, cranium, clavicle
- Bone can vary in density:
 Spongy bone consists of open, interlacing framework of bony tissue, oriented to give strength
 Compact bone is dense –the open framework of spongy bone has been filled in by additional calcium salts
- Between the rings are lacunae (cavities) filled with osteocytes (bone cells) connected by tiny passageways that
distribute nutrients (canaliculi)
- Bone is a dynamic tissue
 Osteoclasts are bone destroying/resorbing cells
 Osteoblasts are bone forming/building cells.
 Both processes occur together so that new osteons are formed as old ones are resorbed.
- Hormones (parathyroid hormone for resorption and calcitonin for deposition) are responsible for maintaining a
constant calcium level in the blood

Vertebrate Skeleton

- The vertebral column serves as the main stiffening axis

- In fishes it provides points for muscle attachment, provides stiffness, and preserves body shape during muscle
contraction
- Most vertebrates have paired appendages
- Pectoral and pelvic fins in fishes supported by the pectoral and pelvic girdles
- Tetrapods have two pairs of pentadactyl limbs(although they may be highly modified through bone loss or fusion)
- The pelvic girdle is generally firmly attached to the axial skeleton, while the pectoral girdle is more loosely attached

Axial skeleton

- includes the skull, vertebral column, ribs, and sternum

Appendicular skeleton
 - includes the limbs and pectoral and pelvic girdles

Human skeleton is composed of 206 bones

5 Types of Bones

- Long, Short, Flat, Irregular, Sesamoid

- Long bones are longer than they are wide and work as levers. The bones of the upper and lower extremities
( humerus, tibia, femur, ulna, metacarpals, etc.) are of this type.
- Short bones are short, cube-shaped, and found in the wrists and ankles.
- Flat bones have broad surfaces for protection of organs and attachment of muscles (ex. cranial bones, ribs, and bones
of hip and shoulder girdles).
- Irregular bones are all others that do not fall into the previous categories. They have varied shapes, sizes, and surface
features and include the bones of the vertebrae and a few in the skull

Animal Movement

- Most animal movement depends on contractile proteins which can change their shape to relax or contract
- These fibrils will contract when powered by ATP
- Actin and myosin form a contractile system found in most animals
- Cilia and flagella utilize different proteins called tubulin.

Amoeboid Movement

- Ameboid movement is found in ameobas, white blood cells, and embryonic cells
- Movement using pseudopods (false feet) depends on actin and myosin
- Cilia are found throughout the animal kingdom (except in nematodes, rare in arthropods)
 Uniform in diameter (0.2-0.5 μm) and structure
 Basal body similar to a centriole – 9 triplets of microtubules composed of the protein tubulin
 Cilium has 9 pairs surrounding two individual microtubules

Ciliary and Flagellar Movement

- A flagellum is a whiplike structure longer than a cilium and usually present singly
- Structure is the same
- Different beating pattern

Muscle Contraction

- One motor neuron has many terminal branches that may innervate many muscle fibers
- A motor unit includes the motor neuron and all the fibers it innervates

The Neuromuscular Junction

- The place where a motor axon terminates on a muscle fiber is called the neuromuscular junction
- The synaptic cleft is a small gap that separates the nerve fiber & muscle fiber
- Acetylcholine is stored in synaptic vesicles in the neuron
- When a nerve impulse arrives, acetylcholine is released into the cleft starting a wave of depolarization in the muscle
fiber

Excitation-Contraction Coupling

- In the resting state, muscle shortening does not occur because thin tropomyosin strands on the actin myofilaments lie
in a position that prevents the myosin heads from attaching to actin 87
- When the muscle is stimulated, calcium ions are released that bind to troponin
- This causes a change in shape that causes the tropomyosin to move out of the way exposing binding sites on the actin
molecule
Energy for Contraction

- Energy for muscle contraction comes from ATP

- ATP is synthesized during aerobic metabolism
- During prolonged exercise, blood flow can’t

supply oxygen fast enough for aerobic metabolism to continue

- Anaerobic glycolysis is not as efficient, but still produces some ATP

- An oxygen debt builds up because the accumulated lactic acid must be oxidized

Fast and Slow Fibers

- Skeletal muscles consist of different types of fibers

- Slow oxidative fibers (red muscles) specialized for slow, sustained contractions

Maintaining posture

- Fast glycolytic fibers (white muscles) lack an efficient blood supply and function anaerobically
 Running muscles in cats
- Fast oxidative fibers have an efficient blood supply and function aerobically for fast, sustained activities
 Wing muscles in migratory birds.