Anatomy & Physiology: Introduction, Tissues, Integumentary System, and Skeletal System Study Notes

Anatomy & Physiology Overview

Definitions and Interrelation

Anatomy is the study of the structure of body parts and their relationships to one another. Physiology is the study of the function of body parts and how they work to carry out life-sustaining activities. These disciplines are closely interrelated because the structure of a body part often determines its function.

• Anatomy: Focuses on body structures, such as organs and tissues.

• Physiology: Explores how those structures function and interact.

• Example: The anatomy of the heart (chambers, valves) enables its physiological role in pumping blood.

Levels of Structural Organization

The human body is organized into several levels, each building on the previous one:

• Atoms & Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organism

• Example: Muscle cells form muscle tissue, which makes up organs like the heart.

Homeostasis

Homeostasis is the maintenance of stable internal conditions despite changes in the external environment. It is essential for survival and proper function.

• Example: Regulation of body temperature, blood glucose levels.

• Importance: Disruption can lead to disease or dysfunction.

Tissues

Overview of Tissue Types

The body contains four primary tissue types, each with distinct functions:

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

• Connective tissue: Supports, protects, binds other tissues.

• Muscle tissue: Responsible for movement.

• Nervous tissue: Transmits electrical impulses, controls responses.

Epithelial Tissue Subtypes

Epithelial tissue is classified by cell shape and layering:

• Shapes: Squamous (flat), Cuboidal (cube-shaped), Columnar (tall).

• Layers: Simple (one layer), Stratified (multiple layers).

• Examples:

  • Simple squamous: air sacs of lungs, blood vessels.

  • Stratified squamous: skin, mouth lining.

  • Simple cuboidal: kidney tubules, glands.

  • Simple columnar: digestive tract lining.

Connective Tissue Subtypes

Connective tissue has many subtypes, each with specialized functions:

• Loose connective tissue: Areolar, adipose, reticular.

• Dense connective tissue: Dense regular, dense irregular, elastic.

• Specialized connective tissue: Hyaline cartilage, fibrocartilage, elastic cartilage, bone, blood.

• Functions: Support, protection, transport, insulation.

• Examples:

  • Adipose: stores fat, insulates.

  • Bone: supports, protects, stores minerals.

  • Blood: transports nutrients, gases.

Intercellular Junctions

Cells in tissues are connected by specialized junctions that facilitate communication and maintain tissue integrity.

Junction Type	Anchors to...	Function	Example
Tight	Membranes fuse	Seal, prevent leakage, maintain polarity	Intestine, BBB
Adherens	Actin filaments	Adhesion, resist separation	Epithelia
Desmosomes	Intermediate filaments (keratin)	Strong adhesion, resist stress	Skin, heart
Hemidesmosomes	Basement membrane	Anchor to ECM	Epidermis
Gap	Connexons (channels)	Communication, ion/nutrient flow	Heart, smooth muscle

Exocrine vs. Endocrine Glands

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

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

• Membranes:

  • Cutaneous: Skin (epidermis, dermis, subcutaneous).

  • Mucous: Lines cavities open to exterior (digestive, respiratory tracts).

  • Serous: Covers organs, lines body cavities (pleura, pericardium).

Integumentary System

Functions and Homeostasis

The integumentary system (skin, hair, nails, glands) protects the body, regulates temperature, and maintains homeostasis.

• Protection from trauma, infection, dehydration.

• Sensation (touch, pain, temperature).

• Vitamin D synthesis.

• Thermoregulation.

• Nonverbal communication.

Structure and Function of Epidermis

The epidermis is the outermost layer of skin, made of epithelial tissue. It consists of several layers:

• Stratum basale: Deepest layer, stem cells, mitosis.

• Stratum spinosum: Keratinocytes joined by desmosomes, some mitosis.

• Stratum granulosum: Keratinocytes produce keratin, water barrier.

• Stratum lucidum: Only in thick skin (palms, soles).

• Stratum corneum: Outermost, dead keratinized cells.

Hair and Nails

• Hair: Structure includes shaft, root, follicle. Functions in protection, sensation, and thermoregulation.

• Nails: Hard plates of keratin, protect fingertips.

Skin Glands

Gland Type	Secretion	Function
Sebaceous	Oily (sebum)	Lubricates skin, prevents drying
Eccrine sweat	Watery	Thermoregulation
Apocrine sweat	Thick, protein/lipid-rich	Odor, stress response
Mammary	Milk	Nutrition for infants

Skin Cancer Types

• Basal Cell Carcinoma

• Squamous Cell Carcinoma

• Melanoma

Skeletal System

Functions of the Skeletal System

• Support

• Protection

• Movement

• Electrolyte balance

• Acid-base balance

• Blood formation (hematopoiesis)

Bone Types

• Long bones: Movement, support (e.g., femur).

• Short bones: Stability, support (e.g., carpals).

• Flat bones: Protection (e.g., skull, ribs).

• Irregular bones: Complex shapes (e.g., vertebrae).

• Sesamoid bones: Embedded in tendons (e.g., patella).

Bone Cells and Tissue Structure

• Osteogenic cells: Stem cells, differentiate into osteoblasts.

• Osteoblasts: Build bone matrix, initiate ossification.

• Osteocytes: Mature bone cells, maintain bone tissue.

• Osteoclasts: Break down bone (resorption), large, multinucleated.

Compact vs. Spongy Bone

Feature	Compact Bone	Spongy Bone
Structure	Dense, organized in osteons (Haversian systems)	Porous, lattice-like (trabeculae)
Location	Outer layer of bones	Interior, ends of long bones, flat bones
Function	Strength, protection, weight-bearing	Reduces weight, contains red marrow, absorbs stress
Blood Supply	Central canals, perforating canals	Diffuses through trabeculae; well vascularized

Bone Formation and Growth

• Intramembranous ossification: Bone develops directly from mesenchyme (e.g., flat bones).

• Endochondral ossification: Bone replaces hyaline cartilage model (e.g., long bones).

• Bone growth in length: Occurs at epiphyseal plates (cartilage growth, then ossifies).

• Bone growth in width: Appositional growth (osteoblasts add layers under periosteum).

Bone Remodeling and Mineral Homeostasis

• Bone remodeling is a continuous process of bone resorption and formation, regulated by hormones and mechanical stress.

• Key hormones: Parathyroid hormone (PTH), calcitonin, vitamin D.

• Calcium homeostasis: Maintained by bone resorption (osteoclasts) and deposition (osteoblasts).

• Equation:

$\text{Ca}^{2+} \text{ homeostasis:} \quad \text{Bone resorption} \rightleftharpoons \text{Bone deposition}$

Common Bone Disorders and Fractures

• Osteoporosis: Decreased bone density, increased fracture risk.

• Osteomalacia/Rickets: Defective mineralization, often due to vitamin D deficiency.

• Osteogenesis imperfecta: Genetic disorder, brittle bones.

• Fractures: Classified by pattern (simple, compound, comminuted, etc.).

Bone Repair and Remodeling

• Hematoma formation: Blood clot forms at fracture site.

• Fibrocartilaginous callus: Soft callus forms, stabilizes bone.

• Bony callus: Osteoblasts replace cartilage with spongy bone.

• Bone remodeling: Compact bone replaces spongy bone, reshapes cortex.

Additional info: Some details and examples were expanded for clarity and completeness.