THE HUMAN BODY

Definitions of Anatomy and Physiology

• Anatomy is the study of the structure of body parts and their relationships to one another.

• Physiology is the study of the function of the body’s structural machinery—how the body parts work and carry out their life-sustaining activities.

• Example: Studying the heart’s chambers (anatomy) versus understanding how the heart pumps blood (physiology).

Levels of Organization in the Human Body

• The human body is organized in a hierarchical structure:

• Chemical level (atoms, molecules) → Cellular level (cells) → Tissue level (groups of similar cells) → Organ level (organs) → Organ system level (organ systems) → Organismal level (the whole body).

• Example: Muscle cell → muscle tissue → biceps brachii (organ) → muscular system → human body.

Homeostasis and Homeostatic Controls

• Homeostasis is the maintenance of a stable internal environment despite external changes.

• Negative feedback mechanisms reduce the effect of the original stimulus (e.g., body temperature regulation).

• Positive feedback mechanisms enhance the original stimulus (e.g., blood clotting, labor contractions).

• Example: When blood glucose rises, insulin is released to lower it (negative feedback).

Directional Terms, Body Cavities, Body Planes, and Regions

• Directional terms describe the location of body structures (e.g., anterior/posterior, superior/inferior, medial/lateral).

• Body cavities include the dorsal (cranial and vertebral) and ventral (thoracic, abdominal, pelvic) cavities.

• Body planes are imaginary lines: sagittal (left/right), frontal (anterior/posterior), transverse (superior/inferior).

• Body regions refer to specific areas (e.g., abdominal regions: epigastric, umbilical, hypogastric).

Metabolism, Catabolism, and Anabolism

• Metabolism is the sum of all chemical reactions in the body.

• Catabolism breaks down molecules to release energy.

• Anabolism builds complex molecules from simpler ones, requiring energy.

• Example: Digestion (catabolism) vs. protein synthesis (anabolism).

Central Dogma of Biology

• The central dogma describes the flow of genetic information:

• DNA replication → transcription (DNA to RNA) → translation (RNA to protein).

• Example: The gene for insulin is transcribed to mRNA, which is then translated into the insulin protein.

Tissue Types in the Body

• Four primary tissue types: epithelial, connective, muscle, and nervous tissue.

• Epithelial tissue covers surfaces and lines cavities.

• Connective tissue supports and binds other tissues.

• Muscle tissue enables movement.

• Nervous tissue transmits electrical impulses.

Types and Locations of Epithelial Tissues

• Simple epithelium: single cell layer (e.g., simple squamous in alveoli).

• Stratified epithelium: multiple layers (e.g., stratified squamous in skin).

• Columnar: tall, column-shaped cells (e.g., digestive tract lining).

• Cuboidal: cube-shaped cells (e.g., kidney tubules).

• Transitional: changes shape (e.g., urinary bladder).

Body Membranes

• Membranes cover body surfaces and line cavities:

• Mucous membranes (line cavities open to exterior), serous membranes (line closed cavities), cutaneous membrane (skin), synovial membranes (line joint cavities).

BIOCHEMISTRY

Organic vs. Inorganic Compounds

• Organic compounds contain carbon and hydrogen (e.g., carbohydrates, proteins, lipids, nucleic acids).

• Inorganic compounds do not contain both carbon and hydrogen (e.g., water, salts, acids, bases).

• Example: Glucose (C6H12O6) is organic; NaCl is inorganic.

Chemical Bonds and Their Strengths

• Ionic bonds: transfer of electrons (strong in solid, weak in water).

• Covalent bonds: sharing of electrons (strongest in biological systems).

• Hydrogen bonds: weak attractions between polar molecules (important in DNA structure).

Types of Chemical Equations

• Synthesis reactions: two or more substances combine ().

• Decomposition reactions: a substance breaks down ().

• Exchange reactions: parts of molecules are exchanged ().

CELL MEMBRANE STRUCTURE AND TRANSPORT

Cell Structure and Organelles

• Cells contain organelles such as the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and ribosomes.

• Each organelle has a specific function (e.g., mitochondria produce ATP, ribosomes synthesize proteins).

Cell Membrane: Phospholipid Bilayer and Fluid Mosaic Model

• The cell membrane is composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

• The fluid mosaic model describes the dynamic and flexible nature of the membrane.

Cell Cycle and Phases

• The cell cycle consists of interphase (G1, S, G2) and mitotic phase (mitosis and cytokinesis).

• Proper order: G1 (growth), S (DNA synthesis), G2 (preparation), M (mitosis), C (cytokinesis).

Transport Mechanisms: Active vs. Passive

• Passive transport does not require energy (e.g., diffusion, osmosis, facilitated diffusion).

• Active transport requires energy (ATP) to move substances against their concentration gradient (e.g., sodium-potassium pump).

INTEGUMENTARY SYSTEM

Structures of the Integumentary System

• Includes skin, hair, nails, sweat glands, and sebaceous glands.

Skin Structure and Layers of the Epidermis

• The epidermis has several layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (only in thick skin), and stratum corneum.

• Thick skin (palms, soles) contains all five layers; thin skin lacks the stratum lucidum.

Accessory Structures and Functions

• Sweat glands (eccrine and apocrine) help regulate temperature and excrete waste.

• Sebaceous glands secrete sebum for lubrication.

• Hair provides protection and sensation.

• Nails protect fingertips and enhance sensation.

Cells of the Skin and Their Functions

• Melanocytes produce melanin (pigment).

• Merkel cells are involved in touch sensation.

• Langerhans cells (not listed but important) are immune cells in the skin.

SKELETAL SYSTEM

Functions of the Skeletal System

• Provides support, protection, movement, mineral storage (especially calcium), and blood cell formation (hematopoiesis).

Parts of a Long Bone

• Diaphysis (shaft), epiphyses (ends), metaphysis (between shaft and ends), medullary cavity (contains marrow), periosteum (outer covering).

Cartilage, Ligament, and Tendon

• Cartilage: flexible connective tissue at joints.

• Ligament: connects bone to bone.

• Tendon: connects muscle to bone.

Spongy Bone vs. Compact Bone

• Spongy bone (cancellous): porous, contains trabeculae, found at ends of long bones.

• Compact bone: dense, forms outer layer of bones, provides strength.

Cells of the Skeletal System

• Osteogenic cells: stem cells that differentiate into osteoblasts.

• Osteoblasts: build bone matrix.

• Osteoclasts: break down bone matrix.

Calcium Homeostasis and the Skeletal System

• The skeletal system regulates blood calcium levels through bone remodeling.

• Parathyroid hormone (PTH) increases blood calcium by stimulating osteoclasts.

• Calcitonin lowers blood calcium by stimulating osteoblasts.