lecture 2 support and protection 2nd sem 2008-2009

Lecture 2. Support and Protection

Functions:

1. protective wrapping– mechanical protection against abrasion and

puncture– effective barrier against bacteria– moisture proofing against fluid loss or gain– protect underlying cells against UV

2. regulatory function– temperature regulation

Integumentary System

Functions:

3. information getting– sensory receptors

4. excretory function

5. respiratory function

6. survival

7. behavioral interactions between individuals

Integumentary System

1. Plasma membrane– unicellular protozoa– gas exchange and waste removal by simple diffusion– uptake of dissolved nutrients

Invertebrate Integument

Amoeba

Paramecium

Pellicle– thick protein coat found in other protozoa– offers further environmental protection– semi-rigid structure that transmits the force of cilia

or flagella to the entire body as the animal moves

2. Epidermis– in most multicellular invertebrates– single layer of columnar epithelial cells– some invertebrates have cuticle over the epidermis – delicate and soft in molluscs and contain mucous

glands, some of which secrete calcium carbonate of the shell

Invertebrate Integument

Mantle– pair of folds formed by the dorsal body wall– outer surface secretes shell

– arthropods have the most complex of invertebrate integuments

– for protection and skeletal support

(protein and chitin)

(nonchitinous complex of protein and lipids)

The arthropod cuticle may be hardened by:

1. calcification – deposition of calcium carbonate in the outer layers of procuticle

The arthropod cuticle may be hardened by:

2. sclerotization – protein molecules bond together with stabilizing cross-linkages within and between adjacent lamellae of the procuticle

– formation of a highly resistant and insoluble protein, sclerotin

Molting of arthropods– epidermal cells divide by mitosis– epidermis secretes enzyme to digest procuticle– absorption of digested materials– new epicuticle and procuticle formed– new cuticle is thickened and calcified or sclerotized

Skin and derivatives

Vertebrate Integument

Skin and derivatives

Vertebrate Integument

Epidermis– stratified squamous epithelium– devoid of blood vessels– cells of the basal part undergo frequent mitosis– as outer layer of cells are displaced upward by new

generations of cells beneath, keratinization takes place

– cornified cells, highly resistant to abrasion and water diffusion, comprise the outermost stratum corneum

Dermis– dense connective tissue layer– contains blood vessels, collagenous fibers, nerves,

pigment cells, fat cells, and fibroblasts– support, cushion, and nourish the epidermis– macrophages and lymphocytes provide the first line

of defense

Epidermal derivatives

Dermal derivatives

Similarity of structure of integumentary derivatives

- all are built of similar combinations of epidermal (keratinized) and dermal components

Hairs– epidermal growths that function in protection– shaft, root, and follicle– sebaceous glands, arrector pili muscle, and hair

root plexus (touch)

Hairs• Types

1. Underhair• Dense and soft• For insulation

2. Guard hair• Coarse and longer• For protection against wear and to

provide coloration

Nails• plates of highly packed, keratinized cells• protection, scratching, and manipulation• formed by cells in nail bed called the matrix (in

area of lunula)• 1 mm / week• eponychium - cuticle

Skin Glands• Sebaceous (oil) glands

– usually connected to hair follicles

– fats, cholesterol, proteins, salts, and cell debris

– moistens hair and waterproofs skin

• Sweat (sudoriferous) glands– Eccrine sweat glands

• water, salt, wastes

• hairless regions, scattered

over the body

• function is to cool the body

– Apocrine sweat glands• larger

• associated with hair follicles

• more viscous – fatty acids and proteins

• restricted to armpits and pubic region (humans), breasts, prepuce, scrotum, external auditory canals

• Secretion is correlated with certain activities of the reproductive cycle

• Ceruminous glands– modified sudoriferous glands – secrete cerumen (ear wax)– Cerumen protects the skin of

the ear canal, assists in cleaning and lubrication, and provides protection from bacteria, fungi and insects

Mammary glands• Secrete milk• Thickening of epidermis

Animal coloration– vivid and dramatic when serving as important

recognition marks or warning coloration– subdued or cryptic when used for camouflage

1. Structural color– produced by the physical

structure of the surface tissue; tissue reflects certain light wavelengths and eliminates others

– phase interference effects of the microscopic structure of feathers

– different response depending on the direction or directionality of illumination

A. sunlight B. camera flash

2. color due to pigments– Biochromes – pigments produced by chromatophores– reflect light rays– chromatophores or pigment cells:

• melanophores/melanocytes (melanin)• xanthophores (carotenoid)• iridophores (crystals of purine → silvery or

metallic)

Functions:– support– protection– movement– mineral depot– blood synthesis

Skeletal System

Types:1. Hydrostatic skeleton2. Rigid skeleton

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1. Hydrostatic Skeleton

• Functions– supports body form– provides resistance for the contraction of muscles

to act against• Source

– some organisms use their fluid-filled gastrovascular cavity

– others use their fluid-filled coelom (body cavity)

Hydra with gastrovascular cavity

Earthworm with fluid-filled coelom

Muscular hydrostats– like hydrostatic skeletons,

these work because they are composed of incompressible tissues that remain at constant volume

– muscles arranged in complex patterns

2. Rigid Skeletons

• consist of rigid elements• usually jointed• muscle attachment• 2 principal types

– exoskeleton– endoskeleton

• Exoskeleton - external skeleton– Molluscs - composed of calcium carbonate– Arthropods - composed of chitin– protection and locomotion

• Endoskeleton - internal skeleton– Echinoderms and vertebrates– mineralized bone and cartilage– support, protection, and reservoir of calcium and

phosphorous– grows as the animal grows

üdoes not limit space for internal organsüsupports greater weight

Lancelet, Branchiostoma

Notochord

− semirigid supportive axial rod of protochordates and all vertebrate larvae and embryos

− composed of large vacuolated cells surrounded by elastic and fibrous sheaths

− stiffening device

− except in jawless vertebrates, surrounded or replaced by the back bone during embryonic development

Cartilage− major skeletal element of

some vertebrates− soft, pliable tissue that

resists compression

− jawless vertebrates and elasmobranchs have purely cartilaginous skeletons

Lamprey

Bone− living tissue having significant deposits of calcium salts in the

extracellular matrix− endochondral or replacement bone

− cancellous or spongy bone

− compact bone

− intramembranous bone

− any bone that develops in and replaces cartilage

− any bone that develops without any associated cartilage

− bone composed of thin intersecting lamellae, usually found internal to compact bone

− bone substance that is dense

− i.e. long bone

− i.e. parietal and frontal bones of the face

Long bone

Structure of compact bone

Bone Growth and Renewal• Cartilage structures in early development act as models for

future bones– calcium salts deposited in matrix by cartilage cells and

later by osteoblasts– endochondral ossification

• Osteoclasts– break down bone– remove worn cells– deposit calcium in the blood– work with osteoblasts to heal broken bones

• Role of hormones– somatotropin, calcitonin, parathyroid hormone

Stages of Intramembranous Ossification

Stages of Intramembranous Ossification

Stages of Intramembranous Ossification

Stages of Intramembranous Ossification

Formation of bone collar around hyaline cartilage model.

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Cavitation of the hyaline cartilage within the cartilage model.

Invasion of internal cavities by the periosteal bud and spongy bone formation.

5 Ossification of the epiphyses; when completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages

Formation of the medullary cavity as ossification continues; appearance of secondary ossification centers in the epiphyses in preparation for stage 5.

Hyaline cartilage

Primary ossification center

Bone collar

Deteriorating cartilage matrix

Spongy bone formation

Blood vessel of periosteal bud

Secondary ossification center

Epiphyseal blood vessel

Medullary cavity

Epiphyseal plate cartilage

Spongy bone

Articular cartilage

Stages of Endochondral Ossification

• 2 main divisions– axial skeleton (skull, vertebral column, sternum,

and ribs)– appendicular skeleton (limbs, fins, wings, pectoral

and pelvic girdles)

Plan of the vertebrate skeleton

Human Skeletal System

• Functions– supports and protects the body– permits movement– provides resistive foundation for muscles to act

against

• Bones store calcium and phosphate ions• Certain bones produce red blood cells

55 The Human Skeleton

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The Skull

Vertebral Column

• Vertebral column– supports the head and trunk– protects the spinal cord and roots of spinal nerves

• Segments (from superior to inferior)– cervical - neck– thoracic - chest– lumbar - small of back– sacral – sacrum/pelvic– coccyx – tailbone

• Intervertebral disks of fibrocartilage act as padding

Term # of Vertebrae

Body Area

Abbreviation

Cervical 7 Neck C1 – C7

Thoracic 12 Chest T1 – T12

Lumbar 5 or 6 Low Back L1 – L5

Sacrum 5 (fused) Pelvis S1 – S5

Coccyx 3 Tailbone None

Rib Cage• Protects the heart and lungs, and assists breathing• Support by the thoracic vertebrae

– Twelve pairs of ribs• true ribs

– connect directly to sternum– seven pairs

• “false” ribs– do not connect directly to sternum– five pairs

60 The Rib Cage

The Appendicular Skeleton• Consists of

– the bones within the pectoral and pelvic girdles– the attached limbs

• Pectoral girdle – bones of the shoulder– anterior– supports the arms and hands

• Pelvic girdle - bones of the pelvis– posterior– supports the legs and feet

Bones of the Pectoral Girdle,

the Arm, and the Hand

Bones of the Pelvic Girdle,

the Leg, and the Foot

Classification of Joints• Fibrous Joints (synarthroses)– immovable– between cranial bones, tibia & fibula, radius & ulna

Classification of Joints• Cartilaginous Joints (amphiarthroses)– slightly movable– between vertebrae

Classification of Joints

• Synovial Joints (diarthroses)– freely movable– bones

separated by a cavity

– ball and socket, hinge joints