Comprehensive Study Guide: Introduction to Anatomy & Physiology

Levels of Organization in the Human Body

Directional Terms

Directional terms are used to describe the locations of structures in relation to other structures or locations in the body.

• Superior (Cranial): Toward the head or upper part of a structure.

• Inferior (Caudal): Away from the head or toward the lower part of a structure.

• Anterior (Ventral): Toward the front of the body.

• Posterior (Dorsal): Toward the back of the body.

• Medial: Toward the midline of the body.

• Lateral: Away from the midline of the body.

• Proximal: Closer to the point of attachment or origin.

• Distal: Farther from the point of attachment or origin.

Planes of the Body

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

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

• Midsagittal (Median) Plane: Divides the body into equal right and left halves.

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

• Transverse (Horizontal) Plane: Divides the body into superior and inferior parts.

Body Cavities

Body cavities are spaces within the body that contain internal organs.

• Dorsal Cavity: Includes the cranial cavity (brain) and vertebral cavity (spinal cord).

• Ventral Cavity: Includes the thoracic cavity (heart, lungs) and abdominopelvic cavity (digestive, urinary, reproductive organs).

Feedback Mechanisms

Feedback mechanisms maintain homeostasis by regulating internal conditions.

• Negative Feedback: Reverses a change to keep a variable within a normal range (e.g., body temperature regulation).

• Positive Feedback: Enhances or amplifies a change (e.g., blood clotting, labor contractions).

Chemistry of the Body

Chemical Terminology

Understanding basic chemical terms is essential for studying physiology.

• Atom: The smallest unit of matter.

• Molecule: Two or more atoms bonded together.

• Ion: An atom or molecule with a net electric charge.

• Compound: A substance formed from two or more elements chemically combined.

Chemical Reactions

Chemical reactions involve the making or breaking of chemical bonds.

• Synthesis Reaction: Two or more substances combine to form a new compound. $A + B \rightarrow AB$

• Decomposition Reaction: A compound breaks down into two or more simpler substances. $AB \rightarrow A + B$

• Exchange Reaction: Parts of two molecules are exchanged. $AB + CD \rightarrow AD + CB$

pH

pH measures the concentration of hydrogen ions in a solution, indicating its acidity or alkalinity.

• Acidic: pH < 7

• Neutral: pH = 7

• Basic (Alkaline): pH > 7

Example: Blood has a normal pH of about 7.4.

The Cell

Parts of the Cell

Cells are the basic structural and functional units of life.

• Plasma Membrane: Outer boundary of the cell, regulates entry and exit of substances.

• Cytoplasm: Jelly-like fluid inside the cell containing organelles.

• Nucleus: Contains genetic material (DNA).

Membrane Transport

Substances move across the cell membrane by various mechanisms.

• Passive Transport: Does not require energy (e.g., diffusion, osmosis, facilitated diffusion).

• Active Transport: Requires energy (ATP) to move substances against their concentration gradient.

Organelles

Organelles are specialized structures within cells that perform specific functions.

• Mitochondria: Produce ATP through cellular respiration.

• Ribosomes: Synthesize proteins.

• Endoplasmic Reticulum (ER): Rough ER synthesizes proteins; smooth ER synthesizes lipids.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

• Lysosomes: Contain digestive enzymes.

DNA

DNA (deoxyribonucleic acid) stores genetic information and directs protein synthesis.

• Structure: Double helix composed of nucleotides (adenine, thymine, cytosine, guanine).

• Function: Codes for proteins, which determine cell structure and function.

Histology: Tissues and Membranes

Tissue Types

Tissues are groups of similar cells performing a common function.

• Epithelial Tissue: Covers body surfaces and lines cavities.

• Connective Tissue: Supports, protects, and binds other tissues.

• Muscle Tissue: Produces movement.

• Nervous Tissue: Transmits electrical impulses.

Tissue Classification

Tissues are classified based on structure and function.

• Simple vs. Stratified Epithelium: Single layer vs. multiple layers of cells.

• Loose vs. Dense Connective Tissue: Amount and arrangement of fibers.

Membranes

Membranes are sheets of tissue that cover or line body surfaces.

• Mucous Membranes: Line body cavities open to the exterior.

• Serous Membranes: Line closed body cavities and secrete serous fluid.

• Cutaneous Membrane: The skin.

The Integumentary System

Components of Skin

The skin is composed of multiple layers and associated structures.

• Epidermis: Outer layer, composed of stratified squamous epithelium.

• Dermis: Middle layer, contains connective tissue, blood vessels, nerves.

• Hypodermis (Subcutaneous Layer): Deepest layer, contains fat and connective tissue.

Functions of Skin

• Protection from pathogens and injury

• Regulation of body temperature

• Sensation (touch, pain, temperature)

• Vitamin D synthesis

• Excretion of wastes

Molecules of Skin

• Keratin: Protein that provides strength and waterproofing.

• Melanin: Pigment that protects against UV radiation.

Burns

• First-degree: Affects only the epidermis; redness and pain.

• Second-degree: Affects epidermis and part of dermis; blisters.

• Third-degree: Destroys entire skin layer; may require grafting.

The Skeletal System

Function of Skeletal System

• Support and protection of organs

• Movement (with muscles)

• Mineral storage (calcium, phosphorus)

• Blood cell production (hematopoiesis)

Components of Bone

• Compact Bone: Dense outer layer.

• Spongy Bone: Porous inner layer.

• Bone Marrow: Site of blood cell production.

Bone Growth

• Ossification: Process of bone formation.

• Epiphyseal Plate: Growth plate in long bones.

Types of Bones

• Long Bones: e.g., femur, humerus

• Short Bones: e.g., carpals, tarsals

• Flat Bones: e.g., skull, ribs

• Irregular Bones: e.g., vertebrae

Major Bone Names

• Skull: Frontal, parietal, occipital, temporal bones

• Vertebral Column: Cervical, thoracic, lumbar vertebrae

• Thorax: Sternum, ribs

• Upper Limb: Humerus, radius, ulna

• Lower Limb: Femur, tibia, fibula

Articulations (Joints)

Classification of Joints

• Fibrous Joints: Immovable (e.g., sutures of the skull)

• Cartilaginous Joints: Slightly movable (e.g., intervertebral discs)

• Synovial Joints: Freely movable (e.g., knee, shoulder)

Structure of Joints

• Articular Cartilage: Covers bone surfaces

• Joint Cavity: Contains synovial fluid

• Synovial Membrane: Secretes synovial fluid

• Ligaments: Connect bone to bone

Types of Joints

• Hinge: Elbow, knee

• Ball-and-Socket: Shoulder, hip

• Pivot: Atlas and axis (neck)

• Gliding: Carpals

Levers

Bones and muscles act as levers to produce movement.

• First-class: Fulcrum between effort and load (e.g., neck)

• Second-class: Load between fulcrum and effort (e.g., standing on tiptoe)

• Third-class: Effort between fulcrum and load (e.g., biceps curl)

The Muscular System

Muscle Functions

• Movement

• Posture maintenance

• Heat production

Types of Muscles

• Skeletal Muscle: Voluntary, striated

• Cardiac Muscle: Involuntary, striated, found in heart

• Smooth Muscle: Involuntary, non-striated, found in walls of organs

Muscle Groups

• Agonist: Prime mover

• Antagonist: Opposes the prime mover

• Synergist: Assists the prime mover

• Fixator: Stabilizes the origin

Muscle Structure

• Muscle Fiber: Single muscle cell

• Myofibrils: Contain contractile proteins (actin, myosin)

• Sarcomere: Functional unit of muscle contraction

Electrical Potentials

Muscle and nerve cells use electrical signals for communication.

• Resting Membrane Potential: Difference in charge across the cell membrane at rest.

• Action Potential: Rapid change in membrane potential that propagates along the cell.

The Nervous System

Functions of Nervous System

• Sensory input

• Integration of information

• Motor output

Divisions of Nervous System

• Central Nervous System (CNS): Brain and spinal cord

• Peripheral Nervous System (PNS): Nerves outside the CNS

Synapses

Synapses are junctions where neurons communicate with other cells.

• Chemical Synapse: Uses neurotransmitters

• Electrical Synapse: Direct electrical connection

Brain Anatomy and Functions

• Cerebrum: Higher brain functions (thought, memory)

• Cerebellum: Coordination and balance

• Brainstem: Basic life functions (breathing, heart rate)

Nerves

• Cranial Nerves: 12 pairs, serve head and neck

• Spinal Nerves: 31 pairs, serve rest of body

Sensory Receptors

• Mechanoreceptors: Detect touch, pressure

• Thermoreceptors: Detect temperature

• Photoreceptors: Detect light (in eye)

• Chemoceptors: Detect chemicals (taste, smell)

• Nociceptors: Detect pain

Neurons

• Cell Body: Contains nucleus

• Dendrites: Receive signals

• Axon: Sends signals

The Autonomic Nervous System (ANS)

Divisions

• Sympathetic: "Fight or flight" response

• Parasympathetic: "Rest and digest" response

Receptors

• Adrenergic Receptors: Respond to adrenaline/noradrenaline

• Cholinergic Receptors: Respond to acetylcholine

Functions

• Regulation of involuntary functions (heart rate, digestion, respiratory rate)

The Eye: Anatomy and Function

Anatomy and Function of Parts of the Eye

• Cornea: Transparent front part, refracts light

• Iris: Colored part, controls pupil size

• Pupil: Opening for light entry

• Lens: Focuses light on retina

• Retina: Contains photoreceptors (rods and cones)

• Optic Nerve: Transmits visual information to brain