Lecture 2. Support and Protection
May 31, 2015
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