Introduction to Anatomy & Physiology: Organization, Chemistry, and the Cell

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Introduction to Anatomy & Physiology

Characteristics of Life

Living organisms share several fundamental characteristics that distinguish them from non-living matter. These characteristics are essential for the maintenance and perpetuation of life.

Growth and Development: An increase in the size of cells, number of cells, or amount of material surrounding the cells.
Motion: Movement of the entire body, individual muscles, organs, single cells, or even substances moving in and out of cells.
Metabolism: All chemical processes that occur in the body, including the making and breaking of chemicals. Metabolism includes anabolism (building up) and catabolism (breaking down).
Responsiveness: The ability to detect stimuli and respond to them.
Reproduction: The formation of new cells for growth, repair, or replacement. Involves producing new individuals or new cells.
Organization: The presence of boundaries that separate the inside from the outside. Life becomes more complex as it becomes more organized.

Organization of Life

Levels of Organization

Biological organization is hierarchical, with each level building upon the previous one to create increasing complexity.

Chemical Level: Atoms combine to form molecules with two or more atoms.
Cellular Level: Cells are the basic unit of life, formed from molecules.
Tissue Level: Similar cells work together for a common function.
Organ Level: Two or more tissues combine for a specific function.
Organ System Level: Groups of organs work together for a common function.
Organism Level: All organ systems working together to maintain life.

Factors Needed to Maintain Life

Several factors are essential for the survival and proper functioning of living organisms.

Food and Nutrients: Needed for energy, building cells, and providing materials for cell processes.
Oxygen: Required for chemical reactions, especially in the mitochondria, where it is used to produce ATP (energy).
Water: The main medium for chemical reactions and transport of substances.
Normal Body Temperature: The ideal body temperature is about 98.6°F (37°C). Enzyme activity and metabolic reactions are temperature-dependent.
Pressure: Needed for processes such as breathing (atmospheric pressure) and blood flow (hydrostatic pressure).

Body Cavities

Major Body Cavities

The body is divided into several cavities that house and protect organs.

Dorsal Cavity: Contains the brain and spinal cord.
Ventral Cavity: Contains the visceral organs.
Thoracic Cavity: Contains the heart and lungs, divided by the diaphragm.
Pleural Cavities: Surround the lungs.
Mediastinum: Area between the pleural cavities, containing the heart, esophagus, and trachea.
Pericardial Cavity: Surrounds the heart.
Abdominal Cavity: Contains most digestive organs and kidneys.
Pelvic Cavity: Contains the bladder and internal reproductive organs.

Abdominal Regions and Quadrants

The abdomen is divided into regions and quadrants for anatomical reference.

Region	Main Organs
Right Hypochondriac	Liver, gallbladder, right kidney, small intestine
Epigastric	Stomach, liver, pancreas, duodenum, aorta, esophagus
Left Hypochondriac	Stomach, spleen, left kidney, pancreas, colon
Right Lumbar	Ascending colon, right kidney, small intestine
Umbilical	Transverse colon, small intestine, pancreas, major blood vessels
Left Lumbar	Descending colon, left kidney, small intestine
Right Inguinal	Cecum, appendix, small intestine, right ovary, fallopian tube
Hypogastric	Urinary bladder, sigmoid colon, small intestine, uterus
Left Inguinal	Sigmoid colon, small intestine, left ovary, fallopian tube

Quadrants: ULQ (Upper Left), URQ (Upper Right), LLQ (Lower Left), LRQ (Lower Right)

Homeostasis

Homeostasis is the maintenance of a stable internal environment, essential for survival.

A stimulus produces a change, causing an imbalance.
Receptors detect the change.
Information is sent along the afferent pathway to the control center.
The control center processes the information and signals a response.
Information is sent along the efferent pathway to the effector.
The effector responds to reduce the effect of the stimulus and return the variable to homeostasis.

Features of Life Related to Chemistry

All characteristics of life are directly related to chemistry, including growth, metabolism, reproduction, homeostasis, movement, and organization.

Growth vs. Reproduction

Growth: Increase in size or number of cells.
Reproduction: Process of splitting, where growth is the result.

Matter vs. Mass

Matter: Anything that has mass and occupies space.
Mass: A measure of how much matter is in an object.

Basic Chemistry for Anatomy & Physiology

Structure of an Atom

An atom is made of protons, neutrons, and electrons.
Protons and neutrons are in the nucleus; electrons are in the outer shells.
Valence electrons determine chemical reactivity.

Ions

Ions are atoms with a charge (positive or negative).
Important ions in the body: sodium, potassium, calcium.

Molecules vs. Compounds

Molecules: Two or more atoms bonded together.
Compounds: Molecules made of two or more different elements.

Inorganic Compounds

Not primarily made of carbon; usually small and simple.
Water: Most chemical reactions occur in water.
Salts/Electrolytes: Create ions when put in water; important for muscle contraction, nerve impulses, blood clotting.
Acids and Bases: Create H+ or OH- in water; affect pH balance.
Oxygen: Needed for chemical reactions, especially making ATP.

Organic Compounds

Contain carbon; four main types: carbohydrates, lipids, proteins, nucleic acids.
Carbohydrates: Simple sugars (monosaccharides) or chains (polysaccharides); used for energy and structure.
Lipids: Hydrophobic; used for energy storage, insulation, and cell membranes.
Proteins: Chains of amino acids; serve as enzymes, structural components, and for movement and transport.
Nucleic Acids: DNA and RNA; store and transmit genetic information. ATP is a nucleotide used for energy.

ATP (Adenosine Triphosphate)

ATP is the main energy currency of the cell. It is produced in the mitochondria and used for biological processes such as muscle contraction and active transport.

ATP production requires oxygen and glucose.
ATP is hydrolyzed to release energy:

Cells: Prokaryotic vs. Eukaryotic

Prokaryotic Cells: No nucleus or membrane-bound organelles; smaller (e.g., bacteria).
Eukaryotic Cells: Have a nucleus and membrane-bound organelles; larger (e.g., plants, animals).

Plasma Membrane

The plasma membrane is a double layer of phospholipids with embedded proteins, cholesterol, and carbohydrates. It controls what enters and leaves the cell.

Hydrophilic heads: Face outward toward water.
Hydrophobic tails: Face inward, away from water.
Proteins act as channels, carriers, or receptors.

Transport Across Membranes

Passive Transport

Diffusion: Movement of molecules from high to low concentration.
Facilitated Diffusion: Movement through a protein channel.
Osmosis: Movement of water through a selectively permeable membrane.

Active Transport

Requires energy (ATP) to move substances from low to high concentration.
Often involves protein pumps.

Osmotic Conditions

Hypotonic: Water enters the cell; cell may burst.
Hypertonic: Water leaves the cell; cell shrivels.
Isotonic: Equal water movement; cell remains stable.

Cell Organelles

Organelle	Main Function
Nucleus	Stores DNA; controls cell activities
Nucleolus	Makes ribosomes
Cytoplasm	Contains organelles; site of many reactions
Ribosomes	Protein synthesis
Rough ER	Protein synthesis and modification
Smooth ER	Lipid synthesis
Golgi Apparatus	Modifies, sorts, and packages proteins and lipids
Lysosomes	Digests waste and foreign material
Vacuole	Stores water and other substances
Vesicles	Transports materials within the cell
Mitochondria	Produces ATP (energy)

Summary

Anatomy and physiology study the structure and function of the human body.
Life is organized in hierarchical levels, from atoms to organisms.
Chemistry is fundamental to understanding biological processes.
Cells are the basic unit of life, with specialized organelles for different functions.
Homeostasis and membrane transport are essential for maintaining life.