Anatomy & Physiology Study Guide: Body Organization, Tissues, and Integumentary System

Body Organization and Anatomical Terminology

Anatomical Position and Planes

The anatomical position is a standardized stance used as a reference in describing the locations and relationships of body parts.

• Anatomical Position: The body stands upright, facing forward, arms at the sides with palms facing forward, and feet parallel.

• Body Planes:

  • 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 it into equal halves.

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

• Axial vs. Appendicular Skeleton: The axial skeleton includes the skull, vertebral column, and thoracic cage; the appendicular skeleton includes the limbs and girdles.

Directional Terms: Used to describe the location of one body part relative to another.

• Proximal: Closer to the point of attachment to the trunk (e.g., the elbow is proximal to the wrist).

• Distal: Farther from the point of attachment.

• Superficial: Toward or at the body surface (e.g., muscle is deep to the skin).

• Deep: Away from the body surface.

Body Systems: There are 11 major body systems, each with specific functions (e.g., circulatory, respiratory, nervous, etc.).

Homeostasis

Definition and Feedback Mechanisms

Homeostasis is the maintenance of a stable internal environment within the body.

• Negative Feedback: The most common mechanism; reverses a change to keep a variable within a normal range (e.g., body temperature regulation).

• Positive Feedback: Enhances or amplifies a change (e.g., blood clotting, labor contractions).

Glands

Development, Secretion, and Function

Glands are specialized epithelial cells that produce and secrete substances.

• Development: Glands develop from epithelial tissue during embryogenesis.

• Types of Secretion:

  • Holocrine: Entire cell disintegrates to release its product (e.g., sebaceous glands).

  • Merocrine (Eccrine): Secrete products via exocytosis without losing cellular material (e.g., sweat glands).

  • Apocrine: Part of the cell membrane buds off with the secretion (e.g., mammary glands).

• Function: Glands secrete hormones, enzymes, sweat, oil, and other substances essential for body function.

Embryology

Germ Layers and Tissue Derivation

During embryonic development, three primary germ layers form all tissues and organs:

• Ectoderm: Forms the epidermis and nervous system.

• Mesoderm: Forms muscle, bone, connective tissue, and the cardiovascular system.

• Endoderm: Forms the lining of the digestive and respiratory tracts.

Tissues

Types, Structure, and Function

Tissues are groups of similar cells performing a common function. There are four basic types:

• Epithelial Tissue: Covers body surfaces, lines cavities, and forms glands. Classified by cell shape (squamous, cuboidal, columnar) and layers (simple, stratified).

• Connective Tissue: Supports, binds, and protects organs. Includes loose (areolar, adipose), dense (tendons, ligaments), cartilage, bone, and blood.

• Muscle Tissue: Responsible for movement. Types include skeletal (voluntary), cardiac (heart), and smooth (walls of organs).

• Nervous Tissue: Conducts electrical impulses. Composed of neurons and supporting glial cells.

Loose vs. Dense Connective Tissue:

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

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

Non-traditional Types: Blood and lymph are considered specialized connective tissues.

Integumentary System

Structure, Function, and Histology

The integumentary system includes the skin and its derivatives (hair, nails, glands). It protects the body, regulates temperature, and provides sensory information.

• Histology: Recognize tissue slides of epidermis, dermis, and hypodermis.

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

  1. Stratum corneum

  2. Stratum lucidum (only in thick skin)

  3. Stratum granulosum

  4. Stratum spinosum

  5. Stratum basale

• Cell Types: Keratinocytes (produce keratin), melanocytes (produce melanin), Langerhans cells (immune), Merkel cells (sensory).

• Vitamin D Synthesis: Skin synthesizes vitamin D when exposed to UV light.

• Skin Pigmentation: Determined by melanocytes and types of pigment particles (eumelanin, pheomelanin).

• Keratination: Process by which keratinocytes mature and move to the surface, becoming filled with keratin and eventually sloughing off.

Membranes

Types and Functions

Body membranes line cavities and cover surfaces.

• Cutaneous Membrane: The skin; protects the body surface.

• Serous Membrane: Lines closed cavities; secretes serous fluid to reduce friction (e.g., pleura, pericardium, peritoneum).

• Mucous Membrane: Lines body cavities open to the exterior (e.g., digestive, respiratory tracts); secretes mucus.

Hair & Nails

Structure and Types

Hair and nails are keratinized structures derived from the epidermis.

• Hair Follicle/Sheath Layers: Multiple layers including the inner and outer root sheaths.

• Types of Hair: Lanugo (fetal), vellus (fine, unpigmented), terminal (thick, pigmented).

• Arrector Pili: Small muscles attached to hair follicles; cause "goosebumps" when contracted.

• Nail Structure: Includes nail plate, nail bed, matrix, and lunula.

Cancer & Burns

Types and Characteristics

• Skin Cancer Types: Basal cell carcinoma, squamous cell carcinoma, melanoma.

• Appearance and Development: Each type varies in appearance, frequency, and severity.

• Burns: Classified by depth:

  • Partial Thickness: Involves epidermis and part of dermis.

  • Full Thickness: Involves entire dermis and sometimes underlying tissues.

Receptors

Types and Functions in the Integumentary System

Cutaneous receptors detect various stimuli in the skin.

• Meissner's Corpuscle: Sensitive to light touch.

• Merkel Receptor: Detects steady pressure and texture.

• Pacini (Pacinian) Corpuscle: Detects deep pressure and vibration; located deep in the dermis.

• Ruffini Cylinder: Responds to skin stretch.

• Free Nerve Ending: Primarily senses pain and temperature.

Table: Types of Cutaneous Receptors and Their Functions

Receptor Type	Stimulus Detected	Location
Meissner's Corpuscle	Light touch	Dermal papillae
Merkel Receptor	Pressure, texture	Basal epidermis
Pacinian Corpuscle	Deep pressure, vibration	Deep dermis/hypodermis
Ruffini Cylinder	Skin stretch	Dermis
Free Nerve Ending	Pain, temperature	Epidermis/dermis

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard Anatomy & Physiology curricula.