Chapter 1: The Human Body – An Orientation

1.1 Anatomy and Physiology: Definitions and Relationship

Anatomy is the study of the structure of body parts and their relationships, while physiology is the study of the function of those parts. The two are closely related, as structure determines function (the principle of complementarity).

• Gross (macroscopic) anatomy: Study of large structures visible to the naked eye (regional, systemic, surface anatomy).

• Microscopic anatomy: Study of structures too small to be seen unaided (cytology, histology).

• Developmental anatomy: Study of structural changes throughout the lifespan (embryology focuses on development before birth).

• Specialized branches: Pathological, radiographic anatomy, etc.

• Physiology: Subdivided by organ systems; focuses on cellular/molecular events and applies principles of physics and chemistry.

Example: The structure of the heart (thick muscular walls) enables its function (pumping blood).

1.2 Levels of Structural Organization and Organ Systems

The human body is organized hierarchically:

• Chemical level: Atoms → molecules → organelles

• Cellular level: Cells (basic unit of life)

• Tissue level: Groups of similar cells with a common function

• Organ level: Discrete structures with specific functions

• Organ system level: Groups of organs working together

• Organismal level: The complete living being

There are 11 major organ systems (e.g., integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic/immune, respiratory, digestive, urinary, reproductive), each with distinct functions.

1.3 Requirements for Life and Survival Needs

To maintain life, humans must perform certain functions and meet survival needs:

• Necessary life functions: Maintaining boundaries, movement, responsiveness, digestion, metabolism, excretion, reproduction, growth

• Survival needs: Nutrients, oxygen, water, normal body temperature, appropriate atmospheric pressure

1.4 Homeostasis and Feedback Mechanisms

Homeostasis is the maintenance of a stable internal environment. It is regulated by feedback systems:

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

• Positive feedback: Enhances the original stimulus (e.g., blood clotting)

• Feedforward responses: Anticipate changes and adjust before they occur

Imbalances in homeostasis can lead to disease.

1.5 Anatomical Terms, Directions, and Planes

Standardized anatomical terms describe body positions, directions, regions, and planes:

• Anatomical position: Body erect, palms forward, thumbs outward

• Directional terms: Superior/inferior, anterior/posterior, medial/lateral, proximal/distal, superficial/deep

• Body planes: Sagittal (left/right), frontal (anterior/posterior), transverse (superior/inferior), oblique

1.6 Body Cavities and Membranes

The body contains internal cavities (dorsal and ventral) lined by membranes, housing organs and providing protection:

• Dorsal cavity: Cranial and vertebral cavities

• Ventral cavity: Thoracic (pleural, pericardial, mediastinum) and abdominopelvic (abdominal, pelvic) cavities

• Serous membranes: Parietal (lines cavity walls) and visceral (covers organs), separated by serous fluid

• Abdominopelvic regions/quadrants: Used for clinical reference

Chapter 2: Chemistry Comes Alive

2.1 Matter and Energy

Matter is anything with mass and volume; energy is the capacity to do work (kinetic = movement, potential = stored). Major forms: chemical, electrical, mechanical, radiant.

2.2 Elements and Atomic Structure

• Elements: Unique substances (C, H, O, N = 96% of body mass)

• Atoms: Protons (+), neutrons (0), electrons (–)

• Atomic number: Number of protons

• Isotopes: Same protons, different neutrons; radioisotopes are unstable

2.3 Molecules, Compounds, and Mixtures

• Molecule: Two or more atoms bonded

• Compound: Two or more different atoms bonded

• Mixtures: Physical combinations (solutions, colloids, suspensions)

2.4 Chemical Bonds

• Ionic bonds: Transfer of electrons (cations/anions)

• Covalent bonds: Sharing of electrons (polar/nonpolar)

• Hydrogen bonds: Weak attractions, important in water/protein structure

2.5 Chemical Reactions

• Synthesis (anabolic): A + B → AB

• Decomposition (catabolic): AB → A + B

• Exchange: AB + C → AC + B

• Oxidation-reduction: Electron transfer (basis for ATP production)

• Factors affecting rate: Temperature, concentration, particle size, catalysts

2.6 Inorganic Compounds: Water, Salts, Acids, and Bases

• Water: High heat capacity, solvent, reactivity, cushioning

• Salts: Ionic compounds, electrolytes

• Acids/bases: Release H+ (acids) or OH– (bases); pH scale (0–14)

• Buffers: Resist pH changes

2.7 Organic Compounds: Synthesis and Breakdown

• Dehydration synthesis: Joins monomers, releases water

• Hydrolysis: Breaks polymers, uses water

2.8 Carbohydrates

• Monosaccharides: Simple sugars (glucose)

• Disaccharides: Two monosaccharides (sucrose)

• Polysaccharides: Long chains (starch, glycogen)

• Function: Energy source

2.9 Lipids

• Triglycerides: Energy storage, insulation

• Phospholipids: Membrane structure

• Steroids: Hormones, membrane components

2.10 Proteins

• Structure: Amino acids, peptide bonds, four levels (primary, secondary, tertiary, quaternary)

• Fibrous vs. globular: Structural vs. functional roles

• Enzymes: Biological catalysts, lower activation energy

2.11 Nucleic Acids: DNA and RNA

• DNA: Double helix, genetic material, A-T, G-C base pairing

• RNA: Single strand, protein synthesis, A-U, G-C base pairing

2.12 ATP: The Energy Currency

• ATP: Adenosine triphosphate, stores and transfers energy via phosphorylation

• Cellular work: Transport, mechanical, chemical

Chapter 3: Cells – The Living Units

3.1 Cell Theory and Generalized Cell Structure

Cells are the basic unit of life. All organisms are made of cells, and all cells arise from pre-existing cells. A typical cell has:

• Plasma membrane: Selective barrier

• Cytoplasm: Fluid with organelles

• Nucleus: Control center

Extracellular materials include fluids, secretions, and the extracellular matrix.

3.2 Plasma Membrane Structure

The plasma membrane is a phospholipid bilayer with embedded proteins (fluid mosaic model). Key components:

• Phospholipids: Hydrophilic heads, hydrophobic tails

• Cholesterol: Stabilizes membrane

• Proteins: Integral (transport, channels), peripheral (enzymes, support)

• Glycocalyx: Carbohydrate-rich area for cell recognition

3.3 Intercellular Junctions

• Tight junctions: Impermeable, prevent leakage

• Desmosomes: Anchoring, resist tearing

• Gap junctions: Communication, allow ions/molecules to pass

3.4 Passive Membrane Transport

• Simple diffusion: Nonpolar molecules move through bilayer

• Facilitated diffusion: Uses carrier/channel proteins for polar molecules

• Osmosis: Water movement across membrane

• Tonicity: Isotonic, hypertonic, hypotonic solutions affect cell volume

3.5 Active Membrane Transport

• Primary active transport: Direct use of ATP (e.g., Na+/K+ pump)

• Secondary active transport: Indirect use of ATP via ion gradients

• Vesicular transport: Endocytosis (phagocytosis, pinocytosis, receptor-mediated), exocytosis

3.6 Membrane Potential

Selective ion diffusion creates a voltage (resting membrane potential) across the membrane, mainly due to K+ gradients. Active transport maintains this potential.

3.7 Cell Adhesion Molecules and Membrane Receptors

• CAMs: Attach cells, guide movement, signal immune cells

• Membrane receptors: Contact and chemical signaling (e.g., G protein-coupled receptors)

3.8 Cytoplasmic Organelles

• Mitochondria: ATP production

• Ribosomes: Protein synthesis

• Endoplasmic reticulum: Rough (protein synthesis), smooth (lipid metabolism, detox)

• Golgi apparatus: Modifies, packages proteins/lipids

• Lysosomes: Digestive enzymes

• Peroxisomes: Detoxification

• Cytoskeleton: Structural support, movement (microfilaments, intermediate filaments, microtubules)

• Centrosome/centrioles: Organize microtubules, cell division

3.9 Cellular Extensions

• Cilia: Motile, move substances

• Flagella: Motility (e.g., sperm)

• Microvilli: Increase surface area

3.10 The Nucleus

• Nuclear envelope: Double membrane with pores

• Nucleoli: Ribosome assembly

• Chromatin: DNA + proteins; condenses to chromosomes during division

3.11 The Cell Cycle

• Interphase: G1 (growth), S (DNA synthesis), G2 (prep for division)

• Mitosis: Prophase, metaphase, anaphase, telophase

• Cytokinesis: Division of cytoplasm

3.12 Protein Synthesis

• Gene: DNA segment coding for a polypeptide

• Transcription: DNA → mRNA

• Translation: mRNA → protein (involves tRNA, rRNA)

• Codons: mRNA triplets; anticodons: tRNA triplets

3.13 Cell Destruction and Aging

• Autophagy: Digestion of cell parts

• Ubiquitin-proteasome pathway: Protein degradation

• Apoptosis: Programmed cell death

• Cell aging: Theories include wear-and-tear, mitochondrial, immune, and genetic (telomere shortening)

Developmental Aspects of Cells

• Cell differentiation: Specialization during development

• Hyperplasia: Increased cell number

• Atrophy: Decreased cell/tissue size