Anatomy & Physiology: Foundational Concepts and Tissue Types

Directional Terms and Body Organization

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 origin of the body part or the point of attachment.

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

• Superficial: Toward or at the body surface.

• Deep: Away from the body surface; more internal.

Body Planes

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. The midsagittal (median) plane divides it into equal halves.

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

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

• Oblique Plane: Passes through the body at an angle between the horizontal and vertical planes.

Body Cavities

The body contains several cavities that house and protect internal organs.

• Cranial cavity (contains the brain)

• Vertebral (spinal) cavity (contains the spinal cord)

• Thoracic cavity (contains heart and lungs)

• Abdominopelvic cavity (contains digestive, urinary, and reproductive organs)

• Pleural cavities (each surrounds a lung)

• Pericardial cavity (surrounds the heart)

• Abdominal cavity (contains stomach, intestines, spleen, liver, etc.)

• Pelvic cavity (contains bladder, reproductive organs, rectum)

• Oral cavity (mouth)

• Nasal cavity (nose)

• Orbital cavities (eyes)

Abdominopelvic Quadrants

The abdominopelvic cavity is divided into four quadrants for clinical reference:

• Right Upper Quadrant (RUQ): Contains liver, gallbladder

• Left Upper Quadrant (LUQ): Contains stomach, spleen

• Right Lower Quadrant (RLQ): Contains appendix, right ovary

• Left Lower Quadrant (LLQ): Contains left ovary, sigmoid colon

Chemical Foundations

Major Elements in the Human Body

The human body is primarily composed of four elements:

• Oxygen (O)

• Carbon (C)

• Hydrogen (H)

• Nitrogen (N)

These elements are essential for building organic molecules and supporting life processes.

pH Scale

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

• Range: 0 (most acidic) to 14 (most alkaline)

• Neutral: pH 7

• Acidic: pH less than 7

• Basic (Alkaline): pH greater than 7

Organic Macromolecules

Four main types of organic macromolecules are found in living organisms:

• Carbohydrates: Provide energy and structural support

• Lipids: Store energy, form cell membranes

• Proteins: Serve as enzymes, structural components, and signaling molecules

• Nucleic acids: Store and transmit genetic information (DNA, RNA)

Cell Structure and Function

Main Structures of a Cell

• Plasma membrane: Regulates entry and exit of substances

• Cytoplasm: Contains organelles and cytosol

• Nucleus: Contains genetic material (DNA)

• Organelles: Specialized structures (e.g., mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes)

Membrane Junctions

Cells connect to each other via specialized junctions:

• Tight junctions: Prevent leakage between cells

• Desmosomes: Provide mechanical strength

• Gap junctions: Allow communication and passage of ions/molecules

Membrane Transport

• Osmosis: Diffusion of water across a selectively permeable membrane

• Diffusion: Movement of molecules from high to low concentration

• Facilitated diffusion: Transport via membrane proteins

• Active transport: Movement against concentration gradient using energy (ATP)

Purpose: Maintain homeostasis by regulating internal environment.

Osmosis vs. Diffusion

• Osmosis: Movement of water only

• Diffusion: Movement of solutes (molecules or ions)

Cell Division

Mitosis and Cytokinesis

• Mitosis: Division of the nucleus into two genetically identical daughter nuclei

• Cytokinesis: Division of the cytoplasm, resulting in two separate cells

Phases of Mitosis:

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

Tissues

Major Types of Tissues

The human body contains four major tissue types:

• Epithelial tissue: Covers surfaces, lines cavities, forms glands

• Connective tissue: Supports, protects, binds other tissues

• Muscle tissue: Produces movement

• Nervous tissue: Transmits electrical impulses

Epithelial Tissue

• Functions: Protection, absorption, filtration, secretion

• Cell shapes: Squamous (flat), cuboidal (cube-shaped), columnar (tall)

• Arrangements: Simple (single layer), stratified (multiple layers)

Glandular Epithelium

• Endocrine glands: Secrete hormones into the bloodstream (e.g., thyroid gland)

• Exocrine glands: Secrete products into ducts (e.g., sweat glands)

Types of Secretion: Merocrine, apocrine, holocrine

Connective Tissue

• Major types: Connective tissue proper, cartilage, bone, blood

Cartilage

• Hyaline cartilage: Found in nose, trachea, ends of long bones

• Elastic cartilage: Found in ear, epiglottis

• Fibrocartilage: Found in intervertebral discs, pubic symphysis

Membranes

Types of Membranes

• Mucous membranes: Line body cavities open to the exterior

• Serous membranes: Line closed body cavities

• Cutaneous membrane: The skin

Integumentary System

Functions

• Protection

• Regulation of body temperature

• Sensation

• Excretion

• Vitamin D synthesis

• Blood reservoir

Regions and Layers

• Three major regions: Epidermis, dermis, hypodermis

• Epidermis layers: (from deep to superficial) Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (only in thick skin), stratum corneum

• Dermis layers: Papillary layer (superficial), reticular layer (deep)

Pigments and Accessory Structures

• Pigments: Melanin, carotene, hemoglobin

• Accessory structures: Hair, nails, glands (sebaceous, sweat)

Bone and Skeletal System

Functions of Bone

• Support

• Protection

• Movement

• Mineral storage

• Blood cell formation (hematopoiesis)

Types of Bone

• Long bones (e.g., femur)

• Short bones (e.g., carpals)

• Flat bones (e.g., sternum)

• Irregular bones (e.g., vertebrae)

Summary Table: Major Tissue Types

Tissue Type	Main Function	Example
Epithelial	Protection, secretion, absorption	Skin, lining of GI tract
Connective	Support, binding, protection	Bone, blood, cartilage
Muscle	Movement	Skeletal muscle, heart
Nervous	Transmit impulses	Brain, nerves

Additional info: Some details, such as the full list of body cavities and the specific features of cartilage types, were expanded for academic completeness.