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

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

1. Introduction to Anatomy and Physiology

Anatomy and physiology are foundational sciences in understanding the structure and function of the human body. Anatomy focuses on the body's structures, while physiology examines how these structures function.

• Anatomy: The study of body structure and the relationships among body parts.

• Physiology: The study of how the body and its parts work or function.

• Levels of Organization: Chemical, cellular, tissue, organ, organ system, organism.

• Body Planes: Sagittal (left/right), frontal (anterior/posterior), transverse (superior/inferior).

• Directional Terms: Anterior/posterior, superior/inferior, medial/lateral, proximal/distal, superficial/deep.

2. Body Cavities and Membranes

The body is divided into several cavities that house organs and are lined by membranes for protection and compartmentalization.

• Major Body Cavities: Dorsal (cranial and vertebral), ventral (thoracic and abdominopelvic).

• Thoracic Cavity: Contains heart and lungs; divided into pleural cavities (lungs) and pericardial cavity (heart).

• Abdominopelvic Cavity: Contains digestive, urinary, and reproductive organs.

• Serous Membranes: Thin, double-layered membranes that cover organs and line cavities (e.g., pleura, pericardium, peritoneum).

• Visceral vs. Parietal Membranes: Visceral covers organs; parietal lines cavity walls.

3. Homeostasis and Feedback Mechanisms

Homeostasis is the maintenance of a stable internal environment. The body uses feedback mechanisms to regulate physiological processes.

• Homeostasis: The body's ability to maintain stable internal conditions.

• Negative Feedback: Reverses a change to keep a variable within a normal range (e.g., body temperature regulation).

• Positive Feedback: Enhances a change (e.g., blood clotting, childbirth).

4. The Mediastinum and Thoracic Structures

The mediastinum is a central compartment in the thoracic cavity containing vital structures.

• Mediastinum: Area between the lungs; contains the heart, trachea, esophagus, and major blood vessels.

• Thoracic Cavity: Divided into pleural cavities (lungs) and mediastinum.

5. Tissue Types and Characteristics

Tissues are groups of similar cells performing specific functions. There are four primary tissue types in the body.

• Epithelial Tissue: Covers surfaces, lines cavities, forms glands. Functions include protection, absorption, secretion.

• Connective Tissue: Supports, binds, and protects organs. Includes bone, cartilage, blood, adipose tissue.

• Muscle Tissue: Responsible for movement. Types: skeletal, cardiac, smooth.

• Nervous Tissue: Initiates and transmits electrical impulses. Composed of neurons and neuroglia.

5.1 Epithelial Tissue

• Characteristics: Closely packed cells, avascular, high regeneration, polarity (apical/basal surfaces).

• Classification: By layers (simple, stratified) and cell shape (squamous, cuboidal, columnar).

• Functions: Protection (skin), absorption (intestines), secretion (glands).

5.2 Connective Tissue

• General Features: Fewer cells, abundant extracellular matrix, vascular (except cartilage).

• Types: Loose (areolar, adipose), dense (regular, irregular), cartilage, bone, blood.

• Specialized Cells: Fibroblasts, adipocytes, chondrocytes, osteocytes.

• Matrix Components: Fibers (collagen, elastic, reticular), ground substance.

5.3 Muscle Tissue

• Types:

  • Skeletal: Voluntary, striated, attached to bones.

  • Cardiac: Involuntary, striated, found in heart, intercalated discs.

  • Smooth: Involuntary, non-striated, found in walls of hollow organs.

5.4 Nervous Tissue

• Neurons: Conduct electrical impulses.

• Neuroglia: Support and protect neurons.

6. The Integumentary System

The integumentary system includes the skin and its derivatives (hair, nails, glands). It serves as a barrier and plays roles in protection, sensation, and thermoregulation.

• Skin Layers: Epidermis (outer), dermis (middle), hypodermis (subcutaneous, not always considered part of skin).

• Functions: Protection, temperature regulation, sensation, vitamin D synthesis, excretion.

6.1 Epidermis

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

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

• Thick vs. Thin Skin: Thick skin (palms, soles) has five layers; thin skin (rest of body) has four.

6.2 Dermis

• Layers: Papillary (areolar connective tissue), reticular (dense irregular connective tissue).

• Structures: Blood vessels, nerves, hair follicles, sweat and sebaceous glands.

6.3 Hypodermis

• Composition: Adipose and areolar tissue.

• Function: Insulation, energy storage, shock absorption.

6.4 Accessory Structures

• Hair: Types include lanugo (fetal), vellus (fine, unpigmented), terminal (thick, pigmented).

• Nails: Protect distal phalanges, aid in grasping.

• Glands:

  • Sebaceous (oil) glands: Secrete sebum, lubricate skin/hair.

  • Sudoriferous (sweat) glands: Eccrine (thermoregulation, all over body), apocrine (axillary/genital, odor).

7. Skin Conditions and Clinical Considerations

• Stretch Marks: Tearing of dermal collagen, often due to rapid growth or weight gain.

• Burns: Classified by depth:

  • First-degree: Epidermis only (redness, pain).

  • Second-degree: Epidermis and part of dermis (blisters).

  • Third-degree: Full thickness (epidermis, dermis, possibly deeper tissues; may be painless due to nerve damage).

• Vitamin D Synthesis: UV light converts 7-dehydrocholesterol in skin to vitamin D3, important for calcium absorption.

• Common Skin Conditions: Acne, eczema, psoriasis, skin cancer (basal cell carcinoma, squamous cell carcinoma, melanoma).

8. Comparison Table: Epithelial vs. Connective Tissue

Feature	Epithelial Tissue	Connective Tissue
Cellularity	High	Low
Matrix	Minimal	Abundant
Vascularity	Avascular	Usually vascular
Location	Surfaces, linings, glands	Supports, connects, protects

9. Key Formulas and Concepts

• Body Surface Area (BSA) for Burns: Rule of Nines (estimates % of body surface affected by burns).

• Homeostasis Equation (Generalized):

$\text{Homeostasis} = \text{Receptor} \rightarrow \text{Control Center} \rightarrow \text{Effector}$

10. Summary Table: Types of Muscle Tissue

Type	Location	Control	Striations
Skeletal	Attached to bones	Voluntary	Yes
Cardiac	Heart	Involuntary	Yes
Smooth	Walls of hollow organs	Involuntary	No

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