Anatomy & Physiology Study Guide: Human Body Orientation, Cells, and Tissues

Chapter 1: The Human Body: An Orientation

Principle of Complementarity of Structure and Function

The principle of complementarity states that the function of a body part is dependent on its structure. This concept is fundamental in anatomy and physiology, as it explains why anatomical features are shaped the way they are to perform specific functions.

• Definition: Structure determines function; what a structure can do depends on its specific form.

• Example: The thin walls of alveoli in the lungs facilitate gas exchange.

Homeostasis

Homeostasis refers to the body's ability to maintain a stable internal environment despite changes in external conditions. It is essential for survival and proper functioning.

• Components: Stimulus, receptor, afferent pathway, control center, efferent pathway, effector, response.

• Example: Regulation of body temperature, blood glucose levels.

• Equation: $\text{Homeostasis} \rightarrow \text{Receptor} \rightarrow \text{Control Center} \rightarrow \text{Effector} \rightarrow \text{Response}$

Negative Feedback Mechanisms

Negative feedback mechanisms counteract changes in a physiological variable, helping to maintain homeostasis.

• Definition: A process that reduces or reverses the original stimulus.

• Example: Regulation of blood glucose by insulin.

Anatomical Position and Its Importance

The anatomical position is a standard reference posture used to describe locations and directions on the human body.

• Definition: Body standing upright, facing forward, arms at sides, palms facing forward.

• Importance: Provides consistency in anatomical terminology.

Common Regional and Directional Terms

Regional and directional terms are used to describe locations and relationships of body parts.

• Examples: Superior, inferior, anterior, posterior, medial, lateral, proximal, distal.

Body Planes and Sections

Body planes are imaginary lines that divide the body into sections for anatomical study.

• Sagittal Plane: Divides body into left and right parts.

• Frontal (Coronal) Plane: Divides body into anterior and posterior parts.

• Transverse Plane: Divides body into superior and inferior parts.

• Application: Used in medical imaging (CT, MRI).

Body Cavities and Serous Membranes

Body cavities house organs and are lined by serous membranes that reduce friction.

• Main Cavities: Dorsal (cranial and vertebral), ventral (thoracic and abdominopelvic).

• Serous Membranes: Double-layered membranes (parietal and visceral) that line body cavities and cover organs.

• Difference: Parietal membranes line cavity walls; visceral membranes cover organs.

Chapter 3: Cells: The Living Units

Types of Extracellular Fluid

Extracellular fluid surrounds cells and provides nutrients, removes waste, and facilitates communication.

• Examples: Interstitial fluid, blood plasma, cerebrospinal fluid.

Extracellular Matrix

The extracellular matrix is a network of proteins and carbohydrates outside cells, providing structural and biochemical support.

• Components: Collagen fibers, proteoglycans, glycoproteins.

• Function: Supports cell adhesion, communication, and tissue repair.

Plasma Membrane Proteins

Membrane proteins are essential for cell communication, transport, and structural integrity.

• Main Types: Integral (embedded in membrane), peripheral (attached to surface).

• Functions: Channels, carriers, receptors, enzymes, anchors.

Cell Junctions

Cell junctions connect cells and regulate movement of substances between them.

• Main Types: Tight junctions (prevent leakage), desmosomes (anchor cells), gap junctions (allow communication).

Membrane Transport

Membrane transport refers to the movement of substances across the cell membrane.

• Passive Transport: No energy required (diffusion, osmosis, facilitated diffusion).

• Active Transport: Requires energy (primary and secondary active transport, endocytosis, exocytosis).

• Equation (Nernst Equation for Ion Movement): $E = \frac{RT}{zF} \ln \frac{[\text{ion outside}]}{[\text{ion inside}]}$

Resting Membrane Potential

The resting membrane potential is the electrical charge difference across the cell membrane at rest.

• Cause: Unequal distribution of ions (mainly Na+ and K+).

• Role of Na+/K+ Pump: Maintains ion gradients by pumping 3 Na+ out and 2 K+ in.

• Equation: $\text{Na}^+/\text{K}^+ \text{ATPase}: 3\text{Na}^+_{\text{out}} : 2\text{K}^+_{\text{in}}$

Cytoskeleton

The cytoskeleton provides structural support and facilitates movement within cells.

• Main Types: Microfilaments, intermediate filaments, microtubules.

• Function: Cell shape, movement, division, intracellular transport.

Chapter 4: Tissues: The Living Fabric

Characteristics of Epithelial Cells

Epithelial cells form protective barriers and are involved in absorption, secretion, and sensation.

• Main Characteristics: Polarity, specialized contacts, supported by connective tissue, avascular but innervated, high regenerative capacity.

Classification of Epithelial Tissue

Epithelial tissues are classified by cell shape and number of layers.

• Shapes: Squamous (flat), cuboidal (cube-shaped), columnar (tall).

• Layers: Simple (one layer), stratified (multiple layers), pseudostratified (appears layered but is not).

• Locations and Functions: Simple squamous (lungs), stratified squamous (skin), simple cuboidal (kidney tubules), simple columnar (digestive tract).

Glandular Epithelium

Glandular epithelium forms glands that secrete substances.

• Exocrine Glands: Secrete products into ducts (e.g., sweat, salivary glands).

• Endocrine Glands: Secrete hormones directly into blood (e.g., thyroid, pituitary).

• Modes of Secretion: Merocrine (exocytosis), holocrine (cell rupture), apocrine (cell apex pinches off).

Connective Tissue

Connective tissue supports, protects, and binds other tissues.

• Main Functions: Support, protection, insulation, transportation.

• Main Categories: Dense regular, dense irregular, blood, bone, adipose, hyaline cartilage, fibrocartilage.

Muscle Tissue

Muscle tissue is responsible for movement and force generation.

• Main Types: Skeletal (voluntary movement), cardiac (heart), smooth (walls of organs).

Covering and Lining Membranes

Membranes cover and line body surfaces, providing protection and lubrication.

• Main Types: Cutaneous (skin), mucous (lines cavities open to exterior), serous (lines closed cavities).

Tissue Repair

Tissue repair restores structure and function after injury.

• Steps: Inflammation, organization (restores blood supply), regeneration (replacement of tissue).

Regenerative Capacities of Tissues

Tissues vary in their ability to regenerate after injury.

• High Regeneration: Epithelial, bone, areolar connective tissue.

• Moderate: Smooth muscle, dense regular connective tissue.

• Poor: Cardiac muscle, nervous tissue in brain and spinal cord.