general zoology lecture!!

8/3/2019 General Zoology Lecture!!

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7 General Zoology LectureFunctions of the Integuments Protection (from pathogenic invasion, ionizing radiation, desiccation

or

osmotic shock, and physical insult/injury) Excretion (wastes such as urea are excreted through the

integument) Body temperature regulation (thermoregulation)

Immune function (Langerhans cells recognize and ingest foreign

substances that have found their way into the body) Synthesis of Vitamin D (modified cholesterol molecules in the

epidermisare converted to vitamin D)

Cutaneous sensation (sensory receptors provide organismsinformation

about the external environmental condition)

Integuments of Invertebrates

Plasma membrane (outermost covering in some protozoa, wherefood

uptake and exchange of respiratory gases also occur) Rigid pellicle (thick protein coat overlying the plasma membranethat

provides additional protection in Paramecium sp.) Epidermis

epidermis of sponges, jellyfish, flatworms, roundworms, and

earthworms = also functions in respiration molluscan epidermis = secretes the calcium carbonate of the shell

complex integument of cephalopod mollusks (squid and octopuses)consisting of cuticle, simple epidermis, layer of connective tissue,

layer of reflecting cells (iridocytes), and thicker layer of connectivetissue.

Integument of Vertebrates: Skin1. Epidermis (outermost layer)

o Epidermal partso Stratum corneum (variable rows of flat, keratinized, dead cells

that are effective water-repellent barrier and protects underlying


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layer; present in all vertebrates, except among fishes)o Stratum lucidum (several rows of clear, flat, dead cells that

contain eleidin that eventually becomes keratin; occurs only inthe thick skin of the palms and soles of mammals

o Stratum granulosum (consists of 3-5 rows of flat cells

containing keratohyalin which produce a lipid waterproofsealant present in reptiles, birds and mammals)

o Stratum spinosum (prickle-cell layer of 8-10 rows of polyhedralcells with tiny bridges connecting them to adjacent cells;

present in all vertebrates except in fishes)

o Stratum germinativum (single row of cuboidal to columnarcells which undergo rapid cell division;

o Cell typeso Keratinocytes (most numerous epidermal cells)

o Merkel cells (found in association with sensory neurons in the

area where epidermis meets the dermis; sensory receptors)o Langerhans cells (macrophages derived from the bone marrow

and migrate to the epidermis where foreign substances areingested)

o Melanocytes (located at the base of epidermis; for melaninproduction)

2. Dermis (inner, thicker layer beneath the epidermis)

o Epidermal derivatives found in the dermiso Hair/pili (for protection; associated with sebaceous gland and

hair follicle)o Nails (plates of very hard, keratinized and tightly packed cells)

o Horn (paired growths on the head of certain ungulate animalspage 2 of 4

o Beaks (horny outer parts of a birds mouth that stick out fromits head)

o Bills (two pointed jaws protected by a horny covering)

o Claws (curved nail on the end of each toe in birds, somereptiles, and some mammals)

o Scales (flat bony or horny overlapping plates that cover thebodies of some reptiles and birds)

o Feathers (hollow central shaft with numerous interlocking fine

strands on either side)o Hoof(horny material covering the feet of animals such as

horses, deer, and cattle)o Glands (with important secretions)

Sebaceous (secrete oil/sebum; lips, glans penis, labiaminora, eyelid glands, skin of breasts, face, neck, upper

chest)

Sudoriferous or sweat glands [types are eccrine


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(distributed almost all throughout the skin specially inthe palms and soles), apocrine (skin of the armpit, pubic

region, and areolae of breasts), and Ceruminous (ear)o Cutaneous Receptors

Pacinian corpuscles (deep pressure)

Meissners corpuscle (touch) Naked nerve endings (pain and light touch)

Ruffinis corpuscle (heat) End bulb of Krausse (cold)page 3 of 4

3. Hypodermis

also called subcutaneous layer or superficial fasci contains mostly fat cells and sensory nerves such as Pacinian

corpuscles

attaches skin to underlying bones or muscles

8 General Zoology LectureTypes of Animal Skeleton

Hydrostatic skeleton

o fluid based skeleton, similar to a water-filled balloon.

oo located internally in cnidarians (coral, jellyfish etc.) and

annelids (leeches, earthworms etc.), among others, these

animals can move by contracting the muscles surrounding thefluid-filled pouch, creating pressure within the pouch that

causes movement.o

Exoskeleton

o external skeleton that is both water and gas proof

oo may take the form of a shell in mollusks, brachiopods,

foramineferans, and other sarcodine protozoao

o among vertebrates, exoskeleton takes the following forms:

scales of reptiles, fishes andf birds; feathers of birds; hair,


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horns and nails in mammalso

Endoskeleton

o internal skeleton

oo consists of rigid or semi-rigid structures, within the body,

moved by the muscular systemo

o components:

Cartilages are found in parts of the endoskeleton requiringboth stiffness and resiliency, such as the surfaces of joints

Bones are living tissues which are formed from significant

deposits of crystals of insoluble inorganic calcium salsts

mainly hydrated calcium phosphate and protein which ismainly collagen.

Functions of Bone Tissue

SupportThe skeleton, which consists mainly of bone tissue, forms a supportive

framework, giving shape and rigidity to the body.

LocomotionThe bone tissue forms a system of levers to which the voluntary

musclesare attached.

ProtectionIt serves toprotect the soft and delicate organs of the body such asthe

skull protects the brain.

Manufacturing of Blood Cells

Red blood cells are manufacturedin the red bone marrow, which is

situated in the spongy tissue at the ends of long bones. Homeostasis

Bone plays a part in homeostasis because it helps to maintain aconstant

levelof calcium in the blood.General Classifications of Boneso Long Bones -- "longer than they are wide:" clavicle, humerus,

radius,ulna, femur, tibia, fibula, metatarsals, metacarpals. Purpose: provide

support and serve as the interconnected set of levers and linkages thatallow us to create movement. (formed from hyaline/articular cartilage)

o


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o Short Bones: carpals and tarsals: consist mainly spongy bonecovered

with a thin layer of compact bone. Purpose: allow movement, provideelasticity, flexibility, & shock absorption.

o

o Flat Bones: ribs, sternum and scapula. Purpose: protect andprovide

attachment sites for muscles.o

o Irregular Bones: skull, pelvis, and vertebrae. Purposes: support

weight,dissipate loads, protect the spinal cord, contribute to movement and

provide sites for muscle attachment.o

o Sesamoid Bones: a short bone embedded within a tendon or joint

capsule, i.e. patella. Purpose: alter the angle of insertion of themuscle.page 2 of 8

Structure of a Bone

o A long bone consists of a centre piece, the shaft (diaphysis) and a

thickened head (epiphysis) at each end.o

o The heads articulate with other bones in the joints and are coveredwith

a thin layer ofhyaline cartilage.

oo The remainder of the bone is covered with a tough, strong

membrane,the periosteum which is richly supplied with blood vessels. There is

a

small artery which penetrates the shaft near the centre to supply thebone tissue with blood.

oo Beneath the periosteum is a layer of compact bone which is

thicker in

the shaft than in the two heads. The shaft encloses a hollow, themarrow

cavity, which is lined with a thin soft membrane known as theendosteum.

oo The marrow cavity contains a soft tissue richly supplied with fat cells

and blood corpuscles, the yellow marrow.

o


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o The epiphysis of a long bone consist ofspongy (or cancellous)bone

covered with a thin layer of compact bone. This is made up ofbonybars

(or trabeculae) arranged in such a way that they are able to resist

anyforce which a applied upon the bone.

oo Between the bars are many tiny cavities filled with a red marrow

which

contains numerous red blood corpuscles in different stages ofdevelopment.

Microscopic Structure of Compact Boneo The ground substance of bone is arranged in concentrated layers

(lamellae) round the small canals which run parallel to the long axis

(shaft) of the bone.o

o These canals, called Haversian canals, are interconnected with oneanother via Volkmann's canals and contain a blood vessel, a nerve

anda lymph vessel.

o

o Each Haversian canal is surrounded by concentric layers ofbonematrix

(called lamallae) and concentric rings of bone forming cells(osteoblasts).

oo Bone cells remain alive and once they have completely surroundedby the

hard bone matrix, they are called osteocytes.page 3 of 8

o The osteocytes are embedded in fluid-filled cavities within theconcentric

lamellae. These cavities are known as lacunae and occur at regularintervals in these concentric layers of bone tissue. The lacunae are

connected to one another and to the Haversian canals by a system of

interconnecting canals known as canaliculi.o

o Each Haversian canal, its concentric lamellae, lacunae withosteocytes

and canaliculi forms a long cylinder and is called a Haversiansystem.

Separate Haversian systems are joined to each other by means of

interstitial lamellae.


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Growth of Bone Tissueo In a child, a long bone has a layer of cartilage between the head

(epiphysis) and the shaft (diaphysis). The cartilage grows activelywhich

causes an increase in the length of the bone.

oo The layer does not thicken since the edges (on both sides) are

constantly replaced by bone (become ossified). The bone grows inthe

length until the child reaches its adult size.

oo The cartilage then also ossifies and disappears. At the same time

thebone increases in thickness as a result of the formation of bone

tissue

immediately beneath the periosteum.o

o The innermost layer, nearest to the marrow cavity, are constantlyabsorbed, which enlarges the size of the marrow cavity.

Classification of Joints

o immovable (fibrous) joints, e.g. skull bones;o slightly movable (cartilagenous) joints, e.g. intervertebral discs;

o freely movable (synovial) joints, e.g. limb joints. Synovial jointspermit

the greatest degree of flexibility and have the ends of bones covered

witha connective tissue (synovial membrane) filled with joint (synovial)

fluid.A typical synovial joint has four main features:

ojoint capsule - the joint enclosure, reinforced by and strengthened

with ligamentsosynovial membrane - a continuous sheet of connective tissue lining

the capsule; its cells produce synovial fluid that lubricates the jointand prevents the two cartilage caps on the bones from rubbing

together

osynovial fluid- produced by the synovial membrane, the fluidlubricates the joint. In the normal joint, very little fluid (less than 5cc)

exists in the cavity.o hyaline (articular) cartilage - where the bones actually "meet"page 6 of 8

Human Skeleton

o Axial Skeleton (80 bones)


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skull - consiting of 1) the cranium (which encloses and protects thebrain) and 2) the facial skeleton. The upper teeth are embedded in the

maxilla; the lower teeth, in the mandible.

mandible (jaw) - the only freely movable bone of the skull

ribs, sternum (breastbone) - comprising the "thorax"/thoracic cage,

protecting the heart and lungs vertebral column - the "spine"

o Appendicular Skeleton (126 bones, 64 in the shoulders and upperlimbs and 62 in the pelvis and lower limbs)

Upper Extremity - The arms (humerus - upper arm bone) are

ultimately attached to the thorax, via synovial joints, at thecollarbone (clavicle) and shoulder bone (scapula) (shoulder joint). The

scapula is attached to the thoracic cage only by muscles. The elbowjoint unites the humerus with the two lower arm bones - the ulna and

radius. Three sets of joints connect the radius and ulna to the bones

of the palm (metacarpals), via the eight small wrist carpals. Further,the knuckles (metacarpophalangeal, or MCP, joints) connect the

metacarpals to the proximalphalanxof the fingers. Each finger has 3phalanges (proximal, middle, distal), except the thumb which has only

two.

o shoulder/ scapula

o arm and forearm, elbow

o hand

Lower Extremity - The pelvis transmits the upper body weight from

the sacrum (at the sacroiliac joint) to the legs. It begins as 3 hip bones

(ilium, ischium, andpubis) which fuse together when growth iscompleted. The hip joint unites the pelvis to the thigh bone (femur);

the knee joint, which includes the knee cap (patella), links the femurto the lower leg bones - the tibia and fibula. The ankle joint links the

lower leg bones to the talus. The body weight is then transmitted to

the heel (calcaneous) and to the balls of the feet via the tarsalandmetatarsalfoot bones. The toes have a phalangeal structure like the

fingers.

o pelvic girdle

o thigh and leg. knee,

o foot/ankle/toe

general zoology lecture!!

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