Introduction to Anatomy and Physiology

Fields of Anatomy and Physiology

Anatomy and physiology are foundational sciences for understanding the human body. Anatomy is the study of structure, often referred to as the "naming of parts," while physiology is the study of function, focusing on "how does it work."

• Anatomy: Structure of body parts

• Physiology: Function of body parts

Types/Fields of Anatomy and Physiology

There are several specialized fields within anatomy and physiology:

• Systemic anatomy: Study of individual organ systems

• Regional anatomy: Study by specific body regions

• Surface anatomy: Study of surface markings

• Gross anatomy: Structures visible to the naked eye

• Microscopic anatomy: Structures seen under a microscope

• Histology: Study of tissues

• Cytology: Study of cells

• Cell physiology: Study of cell function

• Neuroanatomy: Study of nervous system structures

• Digestive physiology: Study of digestive functions

Characteristics of Life

All living things share certain characteristics:

• Made of cells

• Show metabolism (anabolic and catabolic processes)

• Can grow (increase in cell number or size)

• Perform excretion (removal of waste)

• Respond to stimuli

• Show movement

• Can reproduce

Levels of Organization

The human body is organized from least to most complex:

• Chemical level

• Cellular level

• Tissue level

• Organ level

• Organ system level

• Organism level

Organ Systems of the Human Body

There are eleven organ systems, each with specific components and functions:

• Integumentary: Protection, vitamin D production, water retention, temperature regulation

• Skeletal: Support, protection, movement, blood cell production, calcium storage

• Muscular: Movement, control of openings, heat generation

• Nervous: Regulation, sensation, movement, higher functions

• Endocrine: Regulation via hormones

• Cardiovascular: Transport of blood, nutrients, wastes

• Lymphatic: Fluid return, immunity

• Respiratory: Gas exchange, acid-base balance

• Digestive: Digestion, absorption, waste removal, balance maintenance

• Urinary: Waste removal, balance maintenance, blood cell production

• Reproductive: Gamete production, hormone secretion, fetal development

Anatomical Position and Bilateral Symmetry

The anatomical position is a standard reference: standing upright, feet shoulder-width apart, arms at sides, head and palms facing forward. Bilateral symmetry means the body can be divided into mirror-image halves along one plane.

Body Region and Directional Terms

Body region terms (e.g., mental for chin) and directional terms (e.g., anterior, posterior, superior, inferior, medial, lateral, superficial, deep) are essential for describing locations and relationships in the body.

• Anterior: Toward the front

• Posterior: Toward the back

• Superior: Toward the head

• Inferior: Toward the tail

• Medial: Closer to the midline

• Lateral: Farther from the midline

• Proximal: Closer to the point of attachment

• Distal: Farther from the point of attachment

• Superficial: Closer to the surface

• Deep: Farther below the surface

Sections and Planes

Body planes are used to describe anatomical cuts:

• Sagittal: Right and left sections

• Midsagittal: Equal right and left halves

• Parasagittal: Unequal right and left sections

• Frontal (coronal): Anterior and posterior sections

• Transverse (horizontal): Superior and inferior sections

• Oblique: Angled sections

Abdominopelvic Quadrants and Regions

The abdomen is divided into quadrants and regions for clinical and anatomical reference:

• Quadrants: Right upper (RUQ), Left upper (LUQ), Right lower (RLQ), Left lower (LLQ)

• Regions: Right/left hypochondriac, epigastric, right/left lumbar, umbilical, right/left iliac, hypogastric

Body Cavities

The body contains several cavities, each housing specific organs:

• Cranial cavity: Brain

• Vertebral (spinal) cavity: Spinal cord

• Thoracic cavity: Heart and lungs

• Pleural cavities: Lungs

• Mediastinum: Heart

• Abdominopelvic cavity: Digestive organs

Serous Membranes

Serous membranes are two-layered membranes with fluid between layers, reducing friction and holding organs in place. The visceral layer contacts the organ, while the parietal layer attaches to surrounding structures. Types include pleural (lungs), pericardium (heart), and peritoneum (abdominal organs).

Homeostasis and Regulation

Homeostasis is the tendency to maintain a stable internal environment. Each variable has a set point and a normal range. Regulation occurs via autoregulation (intrinsic) and extrinsic regulation (nervous and endocrine systems).

Feedback Loops

Feedback loops maintain homeostasis:

• Negative feedback: Opposes change, returns to set point (most common)

• Positive feedback: Magnifies change, moves away from set point (rare, e.g., blood clotting, labor)

Dynamic Equilibrium and Disease

The body is in a state of dynamic equilibrium, always changing within a normal range. Disease occurs when homeostasis cannot be maintained.

Medical Imaging Techniques

Common imaging techniques include:

• X-Ray: Uses radiation to view dense structures

• MRI: Uses magnetic fields for detailed images

• CT (CAT) Scan: Uses X-rays for cross-sectional images

• PET Scan: Shows metabolic activity

• Ultrasound: Uses sound waves for real-time imaging

Histology: The Study of Tissues

Four Basic Types of Tissue

The human body contains four basic tissue types:

• Epithelium: Covers surfaces, forms glands, has polarity, cellularity, regeneration, and secretion

• Muscle: Responsible for movement and force

• Connective: Provides support, storage, cushioning, transport

• Nervous: Generates electrical signals, controls functions

Cell Junctions

Cell junctions include:

• Desmosomes: Resist mechanical stress

• Gap junctions: Allow communication between cells

• Tight junctions: Make spaces impermeable

Glandular Epithelium

Glands are classified as:

• Endocrine: Release hormones into blood

• Exocrine: Release products via ducts

Modes of exocrine secretion:

• Merocrine: Release only product

• Apocrine: Release product plus part of cell

• Holocrine: Release product plus whole cell

Extracellular Matrix and Protein Fibers

The extracellular matrix (ECM) contains protein fibers:

• Collagen: Thick, strong

• Reticular: Thin, supportive

• Elastic: Stretchy, spiral-like

Connective Tissue Cell Types

Connective tissues contain various cell types, each with specific functions.

Muscle Tissue Types

Muscle tissue is classified as skeletal, cardiac, or smooth, each with unique functions and locations.

Nervous Tissue

Nervous tissue consists of neurons (signal transmission) and neuroglial cells (support).

Histology Terms

• Regeneration: Replacement of damaged tissue

• Fibrosis: Formation of scar tissue

• Scar: Result of fibrosis

• Cancer: Uncontrolled cell growth

Germ Layers

Three primary germ layers give rise to adult tissues:

• Ectoderm: Skin, nervous tissue

• Mesoderm: Muscle, connective tissue

• Endoderm: Digestive and respiratory linings

The Integumentary System

Functions and Layers of Skin

The integumentary system protects, regulates temperature, and produces vitamin D. Skin has multiple layers:

• Epidermis: Outer layer, contains various cell types

• Dermis: Inner layer, contains accessory structures

Epidermal Cell Types and Pigments

Cell types include keratinocytes, melanocytes, and others. Pigments include melanin, carotene, and hemoglobin.

Skin Growth and Types

Skin grows via cell division; thick and thin skin differ in structure and location.

Dermis Structure and Accessory Structures

The dermis contains connective tissue, glands, hair follicles, and nails.

Cleavage Lines and Skin Cancer

Cleavage lines are important in surgery. Types of skin cancer vary in severity.

Hair, Nails, and Glands

Hair follicles and nails grow from specialized structures. Glands include sweat and sebaceous glands.

Body Temperature Regulation

The skin regulates temperature via sweat and blood flow.

Burns and Complications

Burns are classified by depth; major complications include fluid loss and infection. The "rule of nines" estimates burn area.

Common Skin Disorders

• Psoriasis, Acne, Jaundice, Cyanosis, Albinism, Erythema, Pallor, Decubitus ulcers, Stretch marks, Callus

The Skeletal System

Functions and Bone Shapes

The skeletal system supports, protects, enables movement, produces blood cells, and stores minerals. Bones are classified by shape: long, short, flat, irregular, sesamoid.

Bone Anatomy and Matrix

Long bones have distinct gross and microscopic anatomy. The bony matrix is composed of collagen and minerals.

Compact vs. Spongy Bone

Compact bone is dense; spongy bone is porous and found at bone ends.

Bone Marrow

Red marrow: Blood cell production; Yellow marrow: Fat storage.

Bone Cells

Types include osteoblasts (build), osteoclasts (break down), osteocytes (maintain).

Bone Formation and Growth

Intramembranous and endochondral ossification are processes of bone formation. Bone growth occurs at growth plates.

Bone Remodeling and Repair

Remodeling is ongoing; repair follows fracture with specific steps.

Calcium Regulation

Calcitonin and PTH regulate calcium levels.

Fracture Types and Skeletal Divisions

Fractures are classified by pattern; bones are part of axial or appendicular skeleton.

Vertebral Column Curvatures

Normal and abnormal curvatures include scoliosis, kyphosis, lordosis.

Pelvic Structure

Male and female pelvis differ in structure.

Bone Disorders

• Osteoporosis, Marfan’s syndrome, scurvy, cleft lip/palate, osteomalacia, rickets, osteomyelitis, herniated disc, spina bifida

Estrogen plays a role in bone health and osteoporosis development.