Chapter 1: The Human Body – An Orientation

Form Determines Function

The study of anatomy and physiology explores the structure and function of the human body. Understanding how form relates to function is foundational in medical science.

• Anatomy: Study of body structures and their relationships.

• Physiology: Study of body functions; how structures work.

• Principle of Complementarity: Structure determines function; function depends on structure.

Levels of Structural Organization

The human body is organized into hierarchical levels, each increasing in complexity.

• Chemical: Atoms, molecules

• Cellular: Cells

• Tissue: Groups of similar cells with a common function

• Organ: Structure made of two or more tissues performing a function

• Organ System: Group of organs working together

• Organism: The complete living being

Key Terms:

• Tissue: Group of similar cells with a common function.

• Organ: Structure made of two or more tissues performing a function.

• Organ System: Group of organs working together.

Requirements for Life

To sustain life, organisms must perform several essential functions.

• Maintaining boundaries

• Movement

• Responsiveness (excitability)

• Digestion

• Metabolism

• Excretion

• Reproduction

• Growth

Key Terms:

• Excitability: Ability to sense and respond to stimuli.

• Metabolism: All chemical reactions in the body.

  • Anabolism: Building up (synthesis).

  • Catabolism: Breaking down.

Survival Needs

Basic requirements for human survival include:

• Nutrients

• Oxygen

• Water

• Normal body temperature

• Appropriate atmospheric pressure

Organ System Functions

Each organ system has specialized functions essential for homeostasis and survival.

• Respiratory: O2 in, CO2 out

• Integumentary: External covering, protection

• Digestive: Breaks down food, absorbs nutrients, eliminates waste

• Muscular: Movement, posture, heat production

• Urinary: Filtration & excretion of wastes

• Lymphatic/Immune: Defense, returns leaked fluids to blood

• Skeletal: Support, protection, framework

• Nervous: Responds to changes via electrical impulses

• Endocrine: Regulates using hormones

• Cardiovascular: Transports blood, nutrients, gases, wastes

• Reproductive: Produces offspring

Homeostasis

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

• 2 key systems: Nervous (impulses) & Endocrine (hormones)

• Variable: Factor/condition being regulated

Control Mechanism (3 parts):

1. Receptor: Detects stimulus

2. Control center: Processes info, decides response

3. Effector: Carries out response

Feedback:

• Negative feedback: Reduces stimulus (e.g., body temp, blood glucose)

• Positive feedback: Enhances stimulus (e.g., labor contractions, blood clotting)

The Language of Anatomy

Standardized anatomical terms describe body positions, directions, and planes for clarity in medical communication.

• Anatomical Position: Body upright, facing forward, feet apart, palms forward, thumbs out.

Directional Terms:

• Superior = above

• Inferior = below

• Anterior = front

• Posterior = back

• Medial = toward midline

• Lateral = away from midline

• Intermediate = between medial & lateral

• Distal = farther from trunk

• Proximal = toward trunk

• Superficial = toward surface

• Deep = away from surface

Divisions of the Body:

• Axial: Head, neck, trunk

• Appendicular: Limbs

Planes:

• Sagittal: Left/right

• Median (midsagittal): Equal halves

• Parasagittal: Unequal halves

• Frontal (coronal): Front/back

• Transverse: Top/bottom

• Oblique: Diagonal

Body Cavities

Body cavities protect organs and allow changes in size and shape.

• Dorsal: Cranial (brain), vertebral (spinal cord)

• Ventral: Thoracic & abdominopelvic

Thoracic cavity subdivisions:

• Mediastinum: Contains pericardial cavity, heart, esophagus, trachea

• Diaphragm: Separates thoracic & abdominopelvic

Abdominopelvic cavity subdivisions:

• Abdominal: Stomach, intestines, spleen, liver

• Pelvic: Bladder, reproductive organs, rectum

Viscera: Internal organs

Serous Membranes

Serous membranes are thin, double-layered membranes lining cavities and covering organs, reducing friction.

• Layers:

  • Parietal: Lines cavity wall

  • Visceral: Covers organ

  • Serous fluid: Reduces friction

• Major membranes:

  • Pleura: Lungs

  • Pericardium: Heart

  • Peritoneum: Abdominopelvic organs

• 4 Abdominopelvic Quadrants:

  • Right Upper (RUQ)

  • Left Upper (LUQ)

  • Right Lower (RLQ)

  • Left Lower (LLQ)

Chapter 2: Chemistry Comes Alive

Basic Chemistry

Chemistry underpins all physiological processes. Understanding energy and matter is essential for studying the human body.

• Kinetic energy: Energy of motion; does work.

• Potential energy: Stored energy; has potential to do work.

• Chemical energy: Stored in chemical bonds (e.g., ATP, glucose).

Elements of the Body

Elements are pure substances composed of one type of atom. The human body is primarily made of a few key elements.

• Atomic symbols for 13 most common elements: O, C, H, N, Ca, P, K, S, Cl, Na, Fe, Mg, I

• 4 elements making up 96% body mass: Oxygen, Carbon, Hydrogen, Nitrogen

Subatomic Particles

• Overall atom charge: Neutral (protons = electrons).

• Electron orbital: 3D region around nucleus where electrons are found.

Key Terms:

• Atomic number: Number of protons.

• Mass number: Protons + neutrons.

• Isotope: Same element, different number of neutrons.

• Radioisotope: Unstable isotope, decays & emits radiation.

Molecules & Compounds

Molecules and compounds are formed by atoms bonding together.

• Molecule: Two or more atoms bonded (O2).

• Compound: Two or more different atoms bonded (H2O, NaCl).

Mixtures

• Solution: Homogeneous mixture (salt water).

  • Solvent: Dissolving medium (water).

  • Solute: Dissolved substance (salt).

• Colloid (emulsion): Heterogeneous, particles don’t settle, scatter light (cytosol, milk).

• Suspension: Large particles that settle (blood, sand in water).

Chemical Bonds

Chemical bonds are energy relationships between atoms, crucial for molecular structure and function.

• Electron shell: Region of orbitals.

• Valence shell: Outermost shell.

• Octet rule: Atoms stable with 8 valence electrons.

3 bond types:

1. Ionic

2. Covalent

3. Hydrogen

Ions:

• Ion: Charged atom (gain/loss of electrons).

• Cation: + charged (lost electrons).

• Anion: – charged (gained electrons).

Bond explanations:

• Ionic bond: Transfer of electrons (NaCl).

• Covalent bond: Sharing of electrons.

  • Single bond = 1 pair shared.

  • Double bond = 2 pairs shared.

• Nonpolar covalent: Equal sharing.

• Polar covalent (dipole): Unequal sharing → partial charges.

• Electronegativity: Tendency to attract electrons.

• Hydrogen bond: Weak attraction between H (partially +) and O/N (partially –).

Surface tension: Due to many H bonds in water.

Biological molecules with H bonds: DNA, proteins

Chemical Reactions

Chemical reactions involve making or breaking bonds, transforming reactants into products.

• Reactants: Starting substances.

• Products: End result.

Reaction types:

• Synthesis (combination): (anabolic).

• Decomposition: (catabolic).

Energy terms:

• Exergonic: Releases energy.

• Endergonic: Absorbs energy.

• Double arrow (): Reversible reaction.

Factors influencing reaction rate:

1. Temperature: ↑ temp = ↑ speed.

2. Concentration: ↑ reactants = ↑ rate.

3. Particle size: Smaller particles = faster reactions.

4. Catalysts: Enzymes lower activation energy.

Biochemistry

Organic Compounds

Organic compounds contain carbon and are unique to living things.

• Large, covalently bonded molecules

• Include carbohydrates, lipids, proteins, nucleic acids

Inorganic Compounds

Inorganic compounds include water, salts, acids, and bases.

• Properties of water:

  • High heat capacity: Resists temp change.

  • High heat of vaporization: Lots of heat needed for evaporation.

  • Excellent solvent: Dissolves ionic & polar molecules.

  • Other properties: Reactivity (hydrolysis, dehydration), cushioning (CSF protects brain).

• Salts: Ionic compounds, dissociate in water, conduct electricity.

• Electrolytes: Ions in solution, conduct electricity.

• Acids vs Bases:

  • Acid: Releases H+ (proton donor).

  • Base: Accepts H+ (proton acceptor, often OH–).

  • Important base in body: Bicarbonate ion (HCO3–).

• pH scale:

  • Range: 0–14

  • Acid: 0–6.9; Neutral: 7; Base: 7.1–14

• Buffers: Resist large pH changes.

Strong vs Weak Acids/Bases

• Strong acids: Completely dissociate (HCl).

• Weak acids: Partially dissociate (H2CO3).

• Strong bases: Completely dissociate (NaOH).

• Weak bases: Partially dissociate (NH3).

Organic Compounds

Organic molecules are built around carbon and contain functional groups that determine their properties.

• Backbone element: Carbon (C)

• Functional groups:

  • –OH: Hydroxyl

  • –COOH: Carboxyl

  • –NH2: Amino

• Polymers/Monomers:

  • Polymer: Chain of monomers

  • Monomer: Building block

  • Dehydration synthesis: Joins monomers, removes water

  • Hydrolysis: Breaks polymers, adds water

Carbohydrates

Carbohydrates are the body's main source of quick energy and are classified by the number of sugar units.

• Groups: Monosaccharides, disaccharides, polysaccharides

• Monosaccharides (1 sugar):

  • Hexoses: Glucose (blood sugar), fructose, galactose

  • Pentoses: Deoxyribose (DNA), ribose (RNA)

• Disaccharides (2 sugars):

  • Maltose: Glucose + glucose

  • Sucrose: Glucose + fructose

  • Lactose: Glucose + galactose

• Polysaccharides (many sugars):

  • Glycogen: Animal starch

  • Starch: Plants

  • Cellulose: Plants, fiber

• Functions: Quick energy source, short-term storage

Lipids

Lipids are hydrophobic molecules important for energy storage, cell membranes, and hormones.

• Elements: C, H, O (less O than carbs)

• Groups: Triglycerides, phospholipids, steroids

Triglycerides:

• Building blocks: Glycerol + 3 fatty acids

• Fatty acid types:

  • Saturated: Single bonds, solid at room temp

  • Unsaturated: Double bonds, liquid at room temp

Phospholipids:

• Like triglycerides, but 1 fatty acid replaced by phosphate group

• Regions: Hydrophilic head + hydrophobic tails

• Found in cell membranes

Steroids:

• 4-ring structure

• Most important: Cholesterol

• Uses: Membrane stability, precursor to hormones/vitamin D

Proteins

Proteins are complex molecules essential for structure, function, and regulation of the body's tissues and organs.

• Elements: C, H, O, N (sometimes S)

• Building blocks: Amino acids

• Functional groups: Amino (–NH2) and carboxyl (–COOH)

• Unique part: R group

• Bond: Peptide bond (via dehydration synthesis)

Structures:

• Primary: Amino acid sequence

• Secondary: Alpha helix, beta sheet (H bonds)

• Tertiary: 3D folding

• Quaternary: 2+ polypeptides

Protein shapes:

• Fibrous (structural, e.g., collagen)

• Globular (functional, e.g., enzymes, antibodies, hormones)

Denaturation: Protein loses shape/function (heat, pH)

Enzymes: Biological catalysts

• Lower activation energy

• Active site binds substrate (specificity)

• Holoenzyme = apoenzyme + cofactor/coenzyme

Reaction steps:

1. Substrate binds active site

2. Enzyme-substrate complex forms

3. Products released, enzyme unchanged

Nucleic Acids

Nucleic acids store and transmit genetic information and direct protein synthesis.

• Elements: C, H, O, N, P

• Classes: DNA & RNA

• Nucleotide parts: Sugar, phosphate group, nitrogen base

Complementary base pairing: A–T, G–C (DNA); A–U, G–C (RNA)

ATP (Adenosine Triphosphate)

ATP is the primary energy molecule of cells, providing energy for cellular processes.

• Function: Primary energy molecule of cells

• Structure: Adenine + ribose + 3 phosphate groups

Equations:

• Hydrolysis (catabolism):

• Dehydration synthesis (anabolism):

Energy source for ATP synthesis: Energy from glucose oxidation