chap 33 lecture Function in Animal Tissues

Evolution and Function in Animal Tissues

Introduction to Evolutionary Concepts

  • Question posed: Does evolution lead to the perfect animal?

  • Explanation of adaptations: Physical structures enhance an animal's chances for survival and reproduction.

  • Overarching theme: Correlation of structure (anatomy) and function (physiology) in biology.

  • Clarification that animal structures may not be perfect but are often just good enough for functioning.

Example: Giraffe's Laryngeal Nerve

  • Description of the anatomical journey: The laryngeal nerve in an adult giraffe travels from the brain, makes a u-turn around the aorta in the chest, and returns to the throat muscles, a distance of about fifteen feet despite being only a foot away from the brain.

  • Adaptation Analogy:

    • Analogous situation: Moving a table away from an outlet. Options include:

    • Unplugging and repositioning (temporary loss of function).

    • Extending the existing cord.

  • Explanation of early embryo similarities between fish and tetrapods:

    • In fish embryos, the laryngeal nerve connects to the developing gills, and in tetrapods, it connects to the larynx.

    • The nerve hooks under the aorta in fish but stretches out in tetrapods due to aortic position changes during development.

Basic Terminology: Anatomy and Physiology

  • Anatomy: The study of structure.

  • Physiology: The study of function.

  • Animals are organized hierarchically, starting at the cellular level and moving up to tissues, organs, and organ systems.

Levels of Organization in Animals

  • Cellular Level: Basic unit of life.

  • Tissues: Integrated groups of similar cells performing a vital function.

    • Tissues combine to form organs.

    • Four main categories of animal tissues:

    • Epithelial tissue (epithelia)

    • Connective tissue

    • Muscle tissue

    • Nervous tissue

Detailed Discussion of Tissue Types

  • Epithelial Tissue:

    • Definition: Sheets of closely packed cells covering body surfaces and lining internal organs and cavities.

    • Shapes of epithelial tissues:

    • Squamous: Flat (like a fried egg).

    • Cuboidal: Tall as wide.

    • Columnar: Taller than wide.

    • Classification based on layers:

    • Simple squamous epithelium: Unicellular layer.

    • Stratified squamous epithelium: Multilayered.

  • Connective Tissue: Six main types:

    • Loose connective tissue: Most widespread, consists of collagen and elastic fibers; connects skin to underlying tissues.

    • Fibrous connective tissue: Densely packed collagen fibers; forms tendons (attaching muscles to bones).

    • Adipose tissue: Stores fat in closely packed cells.

    • Cartilage: Strong, flexible skeletal material; surrounds bone ends.

    • Bone: Matrix of collagen fibers in hard mineral substance (calcium, magnesium, phosphate).

    • Blood: Composed of red/white blood cells and plasma; transports substances throughout the body.

  • Muscle Tissue:

    • Skeletal muscle: Voluntary movements.

    • Cardiac muscle: Involuntary, pumps blood.

    • Smooth muscle: Involuntary, moves internal organs (e.g., intestines).

  • Nervous Tissue:

    • Senses stimuli and rapidly transmits information through neurons.

    • Neurons carry signals as electrical impulses.

    • Other cells support neurons: insulate axons, nourish neurons, regulate fluid.

Organs and Organ Systems

  • Each tissue has specific functions within organs:

    • Example: Heart includes:

    • Muscle tissue generates contractions.

    • Epithelial tissue lines chambers and prevents leaks.

    • Connective tissue gives elasticity and strength.

    • Nervous tissue regulates contractions.

    • Example: Small Intestine:

    • Lined by columnar epithelium; contains connective tissue with blood vessels;

    • Two layers of smooth muscle aid in food propulsion.

    • Contains finger-like projections to increase absorption surface area.

Overview of Organ Systems

  • Organ systems consist of multiple organs and function collaboratively. Key systems:

    • Circulatory System: Heart and blood vessels; delivers oxygen/nutrients, transports wastes.

    • Respiratory System: Exchanges gases.

    • Integumentary System: Skin, hair, nails; protects body from injury and infections.

    • Skeletal System: All bones and cartilage; supports and protects organs.

    • Muscular System: Skeletal muscles; aids in movement and posture.

    • Urinary System: Kidneys and bladder; removes waste, regulates body chemistry.

    • Digestive System: Breaks down food, absorbs nutrients, eliminates waste.

    • Endocrine System: Glands secreting hormones regulating bodily functions.

    • Lymphatic and Immune Systems: Protect against infections.

    • Nervous System: Coordinates body activities by detecting stimuli.

    • Reproductive System: Produces gametes/hormones; supports embryo.

Integumentary System Details

  • Skin Structure: Composed of two layers:

    • Epidermis: Stratified squamous epithelium.

    • Dermis: Dense connective tissue, contains:

    • Hair follicles, oil, and sweat glands.

    • Muscle cells, nerves, sensory receptors, and blood vessels.

  • Functions of Skin:

    • Resists damage, reduces water loss, prevents microbial penetration.

    • Collects sensory information, synthesizes vitamin D, regulates body temperature.

    • Melanin releases in response to UV exposure, contributing to tanning but also increasing risks of skin damage.

Acne and Consumer Awareness

  • Acne results from clogged hair follicles with dead cells and oil.

  • Bacteria (Propionibacterium acnes) exacerbate inflammation leading to pimples.

  • Study involved 19 individuals with significant improvements; however, lacked strong controls, highlighting the importance of proper experimental design in biomedical research.

Structural Adaptations and Environmental Exchange

  • All organisms exchange matter and energy with their surroundings.

  • Small, flat animals can directly exchange with the environment, while larger organisms require increased surface area through folding or branching systems (e.g., respiratory or circulatory systems) for effective nutrient exchange.

Homeostasis and Feedback Mechanisms

  • Homeostasis: Maintenance of internal stability despite external fluctuations (e.g., temperatures from -30 to 10 °C).

  • Negative Feedback Mechanisms: Stabilize internal conditions within small fluctuations around a set point (e.g., body temperature around 37 °C).

    • When temperature rises:

    • Blood vessels in skin dilate.

    • Sweat glands activate.

    • When temperature drops:

    • Skeletal muscles contract (shivering generates heat).

    • Blood vessels constrict to minimize heat loss.

Urinary System: Osmoregulation and Excretion

  • Overview on the introduction of urinary system, emphasizing renal function and the role in maintaining homeostasis in the body.