Zoology Lecture | Protection, Support & Movement
Animal Protection, Support, and Movement
1. Integument Overview
Definition: The integument is the protective outer covering of the animal body, including skin and its derivatives (hair, nails, scales, feathers, horns).
2. Functions of the Integument
Protection: Shields from mechanical and chemical injuries.
Microbial Defense: Prevents invasion by microorganisms.
Temperature Regulation: Aids in maintaining body temperature.
Excretion: Facilitates the removal of waste materials.
Vitamin D Production: Critical for various bodily functions.
Sensory Reception: Senses environmental stimuli.
Movement: Controls the movement of nutrients and gases.
3. Invertebrate Integument
3.1 Basic Structure
Protozoa: Single-celled organisms may have only a plasma membrane (e.g., Amoeba) or an external pellicle (e.g., Paramecium).
Multicellular Invertebrates: Typically possess a single-layered epidermis; some have an outer non-cellular cuticle (e.g., crustaceans).
3.2 Functionality and Growth
Molting: Invertebrates shed old cuticles periodically for growth.
4. Specific Invertebrate Examples
4.1 Molluscs
Epidermis: Delicate, often protected by a shell.
Cephalopods: Complex integument featuring a cuticle and iridocytes for iridescence.
4.2 Arthropods
Structure: Complex integument with a single-layered epidermis and a layered cuticle (procuticle of chitin, epicuticle moisture barrier).
Cuticle Properties: Can be tough or flexible; hardened in decapods due to calcium carbonate deposition.
4.3 Other Invertebrates
Rotifers: Thin and elastic cuticles.
Cnidarians: Thin epidermis with mucous glands; protective calcium carbonate shells (e.g., corals).
Platyhelminthes: Tegument for protection and nutrient ingestion.
Echinoderms: Thin ciliated epidermis over connective tissue dermis.
5. Vertebrate Integument
5.1 Structure
Epidermis: Thin, stratified layer from ectoderm; gives rise to hair, feathers, hooves.
Dermis: Thicker layer from mesoderm; serves to support and nourish epidermis.
5.2 Epidermis Details
Keratin: Tough and flexible protein found in various structures (scales, feathers).
Function: Protects against environmental factors.
6. Dermal Characteristics
Components: Dense connective tissue containing blood vessels, nerves, and cellular structures.
Bone Structures: In some species, dermal bone contributes to armor (e.g., crocodilian skin).
7. Functions of Mammalian Skin
Stratified Epidermis: Highly cornified with blood vessels, nerves, and glands.
Hair Follicles and Sweat Glands: Essential for thermoregulation and sensory function.
Sebaceous Glands: Control skin moisture by secreting sebum.
8. Skeletal Systems
8.1 Skeleton Functions
Support: Provides framework and protection for vital organs.
Blood Cell Formation: Involved in hematopoiesis.
Mineral Storage: Reservoir for calcium and phosphorus.
8.2 Types of Skeletons
Hydrostatic Skeletons: Using coelomic fluids for support (e.g., earthworms).
Rigid Skeletons: Constructs involving exoskeletons and endoskeletons.
9. Bone Structure and Function
9.1 Types of Bone
Compact vs. Spongy Bone: Compact provides strength; spongy bone contains red marrow.
Dynamic Nature: Bone is continually remodeled by osteoclasts and osteoblasts based on hormonal regulation.
10. Muscle Tissue
10.1 Muscle Types
Skeletal Muscle: Voluntary, striated, fatigues quickly.
Smooth Muscle: Involuntary, slower acting.
Cardiac Muscle: Specialized for heart function, involuntary with striations.
10.2 Muscle Contraction Mechanism
Sliding Filament Hypothesis: Actin and myosin filaments interact through cross-bridging, leading to contraction.
Nerve Stimulation: Skeletal muscle contractions are initiated by motor neurons.
11. Energy for Muscle Contraction
ATP Requirement: Muscle contraction relies on ATP, derived from aerobic and anaerobic metabolism depending on activity levels.
12. Types of Muscle Fibers
Slow vs. Fast Fibers: Vary in endurance and efficiency; slow oxidative fibers sustain contractions, fast glycolytic are designed for quick, powerful bursts.