Introduction to Anatomy & Physiology, Histology, and the Integumentary System: Study Notes

Introduction to Anatomy & Physiology

Anatomical Planes

Understanding anatomical planes is essential for describing locations and movements of body parts in a standardized way.

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

• Sagittal Plane: Divides the body into right and left portions. The midsagittal plane divides the body into equal right and left halves, while a parasagittal plane divides it unequally.

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

Directional Terms

Directional terms are used to describe the positions of structures relative to other structures or locations in the body.

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

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

• Superior: Toward the head or upper part of a structure.

• Inferior: Away from the head or toward the lower part of a structure.

• Proximal: Closer to the point of attachment or origin.

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

• Medial: Toward the midline of the body.

• Lateral: Away from the midline of the body.

• Superficial: Toward or at the body surface.

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

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 the heart and lungs (mediastinum, pleural cavities, pericardial cavity).

• Abdominal Cavity: Contains digestive organs such as the stomach, liver, and intestines.

• Pelvic Cavity: Contains the urinary bladder, reproductive organs, and rectum.

Example: The lungs are located in the pleural cavities within the thoracic cavity.

Histology

Overview of Tissue Types

Histology is the study of tissues. The human body is composed of four basic tissue types, each with unique structures and functions.

Epithelial Tissue

• Simple Squamous Epithelium: Single layer of flat cells; allows for diffusion and filtration. Location: Air sacs of lungs, lining of blood vessels.

• Simple Cuboidal Epithelium: Single layer of cube-shaped cells; functions in secretion and absorption. Location: Kidney tubules, glands.

• Simple Columnar Epithelium: Single layer of tall, column-like cells; absorption and secretion. Location: Lining of digestive tract.

• Stratified Squamous Epithelium: Multiple layers; protects underlying tissues. Keratinized: Found in skin (epidermis). Non-keratinized: Found in mouth, esophagus.

• Transitional Epithelium: Multiple layers; can stretch. Location: Urinary bladder.

• Pseudostratified Columnar Ciliated Epithelium: Appears layered but is a single layer with cilia; moves mucus. Location: Respiratory tract.

Connective Tissue

• Loose Connective Tissue: Loosely arranged fibers; supports and binds other tissues. Location: Under epithelia.

• Dense Connective Tissue: Densely packed fibers; provides strength. Location: Tendons, ligaments.

• Bone (Osseous) Tissue: Hard, calcified matrix; supports and protects. Location: Bones.

• Blood: Fluid matrix (plasma) with cells; transports substances. Location: Blood vessels.

• Cartilage: Firm, flexible matrix; supports and cushions. Location: Joints, ear, nose.

Muscle Tissue

• Skeletal Muscle: Long, striated, multinucleated cells; voluntary movement. Location: Attached to bones.

• Cardiac Muscle: Striated, branched cells with intercalated discs; involuntary, pumps blood. Location: Heart.

• Smooth Muscle: Spindle-shaped, non-striated cells; involuntary movement. Location: Walls of hollow organs (e.g., intestines, blood vessels).

Nervous Tissue

• Neurons: Specialized cells that transmit electrical impulses.

• Neuroglia (Glial Cells): Support, protect, and nourish neurons.

Example: Stratified squamous epithelium (keratinized) forms the outer layer of skin, providing protection against abrasion and dehydration.

Integumentary System

Structure and Function

The integumentary system consists of the skin and its accessory structures. It protects the body, regulates temperature, and provides sensory information.

Epidermis

• Five Layers of the Epidermis (from deep to superficial):

  1. Stratum basale (germinativum): Deepest layer; site of cell division.

  2. Stratum spinosum: Provides strength and flexibility.

  3. Stratum granulosum: Contains granules; cells begin to die.

  4. Stratum lucidum: Present only in thick skin (palms, soles).

  5. Stratum corneum: Outermost layer; dead, keratinized cells.

Dermis

• Two Layers of the Dermis:

  • Papillary Layer: Superficial, contains dermal papillae (finger-like projections that increase surface area and contain capillaries and sensory receptors).

  • Reticular Layer: Deeper, dense irregular connective tissue; provides strength and elasticity.

• Dermal Papillae: Projections that form fingerprints and enhance grip.

• Sebaceous Gland: Secretes sebum (oil) to lubricate skin and hair.

• Sweat Gland: Produces sweat for thermoregulation.

• Hair: Provides protection and sensory input.

• Free Nerve Ending: Detects pain, temperature, and touch.

• Lamellated (Pacinian) Corpuscle: Detects deep pressure and vibration.

• Tactile (Meissner’s) Corpuscle: Detects light touch.

• Arrector Pili Muscle: Smooth muscle that causes hair to stand (goosebumps).

Hypodermis (Subcutaneous Layer)

• Hypodermis: Not technically part of the skin; consists mainly of adipose tissue for insulation and energy storage.

Example: The arrector pili muscle contracts in response to cold or emotional stimuli, causing hair to stand upright (goosebumps).