Anatomy & Physiology: Body Cavities, Cells, and Tissues Study Guide

Body Cavities and Anatomical Terminology

Major Body Cavities

The human body contains several major cavities that house and protect vital organs. Understanding their locations and subdivisions is essential for anatomical orientation.

• Thoracic Cavity: The upper portion of the ventral cavity, enclosed by the rib cage. Contains the heart and lungs.

• Abdominal Cavity: The lower, larger portion of the ventral cavity. Contains digestive organs (stomach, intestines, liver, pancreas), and kidneys.

• Pelvic Cavity: Contains reproductive organs and the rectum.

• Superior: Towards the top of the body surface.

• Inferior: Below or lower than another part.

• Anterior (Ventral): Towards the front of the body.

• Posterior (Dorsal): Towards the back of the body.

• Medial: Towards the midline of the body.

• Lateral: Away from the midline of the body.

Planes and Sections

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

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

• Sagittal Plane: Divides the body into right and left sections.

• Midsagittal: Divides the body into equal right and left halves.

• Parasagittal: Divides the body into unequal right and left sections.

Directional Terms

• Bilateral: On both sides of the body (both eyes).

• Unilateral: On one side of the body only.

• Ipsilateral: On the same side of the body as another structure.

• Contralateral: On the opposite side of the body as another structure.

Body Cavity Subdivisions

• Ventral Cavity: Subdivided into thoracic (upper) and abdominopelvic (lower) cavities.

• Abdominopelvic Cavity: Divided into the abdominal cavity and the pelvic cavity.

• Dorsal Body Cavity: Found along the posterior (back) surface of the body, includes the cranial and vertebral cavities.

• Cranial Cavity: Located within the skull, contains the brain.

• Vertebral (Spinal) Cavity: Narrow cavity that runs within the vertebral column (spine) and houses the spinal cord.

Cell Structure and Function

Cell Membrane and Organelles

Cells are the basic structural and functional units of life. Each cell contains specialized structures called organelles that perform specific functions.

• Plasma Membrane: Phospholipid bilayer that separates the cell's interior from the external environment.

• Secretory Vesicles: Store and transport molecules.

• Golgi Apparatus: Proteins are absorbed, modified, packaged, and distributed to their destination in this organelle.

• Cilia: Wave-like sweeping of mucus and debris in the respiratory tract.

• Mitochondria: Powerhouse of the cell, converts food into ATP (energy) via cellular respiration.

• Ribosomes: Produce proteins inside the cell.

• Rough Endoplasmic Reticulum: Produces proteins for cell membrane or secretion.

• Smooth Endoplasmic Reticulum: Synthesizes lipids, helps make lipids and carbs, no ribosomes on it.

• Centrioles: Organize cell division.

• Lysosomes: Contain digestive enzymes to break down waste.

Cell Membrane Components

• Phospholipid Bilayer: Main structural component, with hydrophilic heads and hydrophobic tails.

• Cholesterol: Stabilizes the cell membrane and regulates its fluidity.

• Integral Proteins: Embedded within the membrane, involved in transport and signaling.

• Peripheral Proteins: Attached to the exterior or interior surfaces of the membrane.

Central Dogma of Molecular Biology

• Transcription: Process of creating an mRNA copy from a DNA template.

• Translation: Process of using the mRNA copy to assemble a protein.

Central Dogma: Flow of genetic information from DNA to RNA to protein through transcription and translation.

Embryonic Tissue Layers and Cell Types

Germ Layers

During embryonic development, three primary germ layers form, giving rise to all tissues and organs.

• Ectoderm: Forms the nervous system, epidermis (outer skin), hair, nails, and tooth enamel.

• Mesoderm: Forms muscle, bone, cartilage, blood, heart, circulatory system, kidneys, and gonads.

• Endoderm: Forms the lining of digestive and respiratory tracts, liver, pancreas, and thyroid.

Stem Cells and Blastocyst

• Zygote: A single, diploid cell containing the complete genetic blueprint from both egg and sperm.

• Morula: Solid, multicellular ball of cells, or blastomeres, formed by rapid cell division after fertilization.

• Blastocyst: Hollow ball of cells consisting of an inner cell mass (embryoblast) and an outer layer (trophoblast).

Tissues: Types, Structure, and Function

Major Tissue Types

The body is composed of four main tissue types, each with specialized functions.

• Epithelial Tissue: Covers and lines organs and body surfaces. Functions in protection, absorption, secretion, filtration, and sensation.

• Connective Tissue: Supports and binds other tissues. Includes bone, blood, and adipose tissue.

• Muscle Tissue: Contracts to produce movement. Includes skeletal, smooth, and cardiac muscle.

• Nervous Tissue: Transmits and receives electrical impulses. Includes neurons and glial cells.

Epithelial Tissue: Structure and Classification

• Cellularity: Composed almost entirely of tightly packed cells with minimal intercellular matrix.

• Polarity: Cells have top (apical) and bottom (basal) surfaces.

• Attachment: Basal surface attached to a thin, supportive basement membrane.

• High Regenerative Capacity: Epithelial cells can rapidly repair and regenerate due to high mitotic rate.

Classification by Layers

• Simple Epithelium: Single layer of cells, specialized for absorption and secretion.

• Stratified Epithelium: Two or more layers, providing strong protection (e.g., skin).

• Pseudostratified Epithelium: Appears layered but all cells touch the basement membrane.

• Transitional Epithelium: Specialized for stretching and recoiling (e.g., urinary organs).

Classification by Cell Shape

• Squamous: Flat, thin cells (e.g., lining blood vessels).

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

• Columnar: Tall, rectangular cells (e.g., lining intestines).

Functions of Epithelial Tissue

• Protection: Shields underlying tissues from mechanical and chemical stress.

• Absorption: Uptake of nutrients and fluids (e.g., intestines).

• Secretion: Release of substances (e.g., glands).

• Filtration: Selective movement of substances (e.g., kidney glomeruli).

• Sensation: Contains sensory nerve endings.

Glandular Epithelium

• Exocrine Glands: Secrete products onto epithelial surfaces or into ducts (e.g., sweat, salivary glands).

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

Cell Junctions and Surface Specializations

Types of Cell Junctions

• Tight Junctions: Seal adjacent cells, prevent molecules and water from passing between cells.

• Desmosomes: Provide strong mechanical strength and resistance to shearing forces.

• Gap Junctions: Allow direct communication and passage of ions, water, and small molecules between cells.

Surface Specializations

• Microvilli: Increase surface area for absorption (e.g., small intestine, kidneys).

• Cilia: Move substances across epithelial surfaces (e.g., respiratory tract, fallopian tubes).

Connective Tissue

General Features

• Matrix: Composed of protein fibers and ground substance, provides support and strength.

• Fibroblasts: Most common cell type, responsible for producing fibers.

• Types of Fibers: Collagen (strength), elastic (flexibility), reticular (support).

Types of Connective Tissue

• Loose Connective Tissue: Fewer fibers, more ground substance (e.g., areolar, adipose tissue).

• Dense Connective Tissue: More fibers, less ground substance (e.g., tendons, ligaments).

• Specialized Connective Tissue: Includes bone, cartilage, blood.

Muscle and Nervous Tissue

Muscle Tissue

• Skeletal Muscle: Voluntary movement, striated, attached to bones.

• Cardiac Muscle: Involuntary, striated, found only in the heart.

• Smooth Muscle: Involuntary, non-striated, found in walls of hollow organs (e.g., intestines, blood vessels).

Nervous Tissue

• Neurons: Transmit electrical impulses.

• Glial Cells: Support, protect, and nourish neurons.

Summary Table: Major Tissue Types and Functions

Tissue Type	Main Function	Location Example
Epithelial	Protection, absorption, secretion, filtration, sensation	Skin, lining of GI tract, glands
Connective	Support, binding, storage, transport	Bone, blood, adipose tissue
Muscle	Movement, posture, heat production	Skeletal muscles, heart, digestive tract
Nervous	Communication, control, sensation	Brain, spinal cord, nerves

Additional info: Some content was inferred and expanded for clarity and completeness, especially regarding cell structure, tissue types, and embryonic development.