الفصل 40: مبادئ الشكل والوظيفة الحيوانية

Chapter 40: Basic Principles of Animal Form and Function

• This chapter discusses the fundamental principles of animal structure and function.
• It details the hierarchical organization of body plans, from cells to tissues, organs, and organ systems.
• Animals possess specialized cells that form tissues, each with specific functions.
• Vertebrates have interstitial fluid filling spaces between cells, facilitating material movement.
• Tissues combine to create organs, and organ systems coordinate bodily functions.

Organ Systems (Table 40.1)

• Digestive: Processes food (ingestion, digestion, absorption, elimination).
• Circulatory: Distributes materials internally, using the heart, blood vessels, and blood.
• Respiratory: Enables gas exchange (oxygen intake and carbon dioxide release).
• Immune and Lymphatic: Defends the body against infections and cancers.
• Excretory: Disposes of metabolic wastes and regulates blood osmotic balance.
• Endocrine: Coordinates body activities via hormones.
• Reproductive: Enables reproduction.
• Nervous: Coordinates body activities by detecting stimuli and formulating responses.
• Integumentary: Protects against injury, infection, and drying, and regulates temperature.
• Skeletal: Provides support and protection.
• Muscular: Enables movement.

Tissue Structure and Function

• Tissues have distinctive structures tailored to specific functions.
• Tissues are broadly categorized into four types: epithelial, connective, muscle, and nervous.

Epithelial Tissue

• Covers the body's exterior and lines internal organs and cavities.
• Classified based on cell layers (simple or stratified).
• Cell shapes include cuboidal, columnar, and squamous.
• Specialized functions include absorption and secretion.

Connective Tissue

• Primarily binds and supports other tissues.
• Contains sparsely distributed cells embedded in an extracellular matrix.
• Matrix composition includes fibers (collagen, elastic, reticular) in a liquid, jelly-like, or solid ground substance.
• Major types include loose connective tissue, cartilage, fibrous connective tissue, bone, and adipose tissue.

Muscle Tissue

• Consists of long fibers that contract in response to nerve signals.
• Types include skeletal, smooth, and cardiac muscle, responsible for voluntary and involuntary movements.

Nervous Tissue

• Senses stimuli and transmits signals throughout the animal.
• Composed of neurons (nerve cells) for signal transmission and glial cells for support and nourishment.

Coordination and Control

• Coordination and control rely on both the nervous system and endocrine system.
• The endocrine system transmits chemical signals (hormones) via the bloodstream.
• Hormones act slowly but have long-lasting effects.
• The nervous system transmits information rapidly and precisely via nerve impulses.

Homeostasis

• Maintaining a stable internal environment, regardless of external changes.
• Variables like body temperature, blood pH, and blood glucose are maintained at constant levels in humans.
• Mechanisms like negative feedback are crucial for maintaining homeostasis.

Thermoregulation

• Maintaining a tolerable internal temperature.
• Endothermic animals generate heat internally (e.g., birds, mammals).
• Ectothermic animals gain heat from external sources (e.g., many invertebrates, fish, amphibians, and reptiles).

Balancing Heat Loss and Gain

• Heat exchange occurs through conduction, convection, radiation, and evaporation.
• Mammals frequently use the integumentary system (skin, hair, nails) for thermoregulation.

Insulation

• Skin, fur, feathers, and blubber reduce heat exchange between the animal and its environment.

Circulatory Adaptations

• Blood flow regulation near the body surface significantly influences thermoregulation.
• Vasodilation increases blood flow for facilitating heat loss.
• Vasoconstriction reduces blood flow to decrease heat loss.
• Evaporative cooling (sweat, panting) is an important heat loss mechanism.

Adjusting Metabolic Heat Production

• Some animals adjust their metabolic heat production to regulate body temperature.
• Muscle activity (shivering) increases metabolic heat production.
• The hypothalamus is the brain region controlling thermoregulation mechanisms (e.g., adjusting body temperature, triggering shivering).
• Fever is an instance of pyrogens resetting the body's thermostat, resulting in increased body temperature