Anatomy & Physiology: Foundational Concepts, Cells, Tissues, and Skeletal System Study Guide

Anatomical Language and Basics

Levels of Organization and Anatomical Terminology

The human body is organized into hierarchical levels, each with specific structural and functional roles. Understanding anatomical language and body regions is essential for describing locations and functions in the body.

• Levels of Organization: The main levels are cells, tissues, organs, organ systems, and the organism itself.

• Body Cavities: Major body cavities include the cranial, thoracic, abdominal, and pelvic cavities. The ventral body cavity is anterior and includes the thoracic and abdominopelvic cavities.

• Membranes: The body contains serous membranes (visceral and parietal) and mucous membranes. Serous membranes line body cavities not open to the exterior; mucous membranes line cavities open to the exterior.

• Anatomical Position and Directional Terms: The anatomical position is standing upright, facing forward, arms at sides, palms forward. Directional terms include anterior/posterior, superior/inferior, medial/lateral, proximal/distal, and superficial/deep.

• Body Planes: The sagittal plane divides the body into right and left, the frontal (coronal) plane divides into anterior and posterior, and the transverse plane divides into superior and inferior parts.

• Abdominal Regions and Quadrants: The abdomen is divided into four quadrants (RUQ, LUQ, RLQ, LLQ) and nine regions (e.g., epigastric, umbilical, hypogastric).

Cells

Cell Structure and Function

Cells are the basic units of life, performing essential activities and forming tissues and organs. Understanding their structure and function is foundational to anatomy and physiology.

• Basic Activities: Cells carry out metabolism, respond to stimuli, grow, reproduce, and maintain homeostasis.

• Chromosome Number: Human diploid cells have 46 chromosomes; haploid cells (gametes) have 23.

• Plasma Membrane: The plasma membrane is a selectively permeable barrier composed of a phospholipid bilayer with embedded proteins. It regulates the movement of substances in and out of the cell.

• Hydrophilic vs. Hydrophobic: Hydrophilic means water-loving (polar), hydrophobic means water-fearing (nonpolar). The plasma membrane has hydrophilic heads and hydrophobic tails.

• Membrane Proteins: Proteins in the membrane serve as channels, carriers, receptors, enzymes, and anchors.

• Endocytosis and Exocytosis: Endocytosis brings substances into the cell; exocytosis expels substances.

• Organelles: Key organelles include the nucleus (genetic control), mitochondria (ATP production), endoplasmic reticulum (protein/lipid synthesis), Golgi apparatus (modification and packaging), and lysosomes (digestion).

• Cytoskeleton: Includes microfilaments, intermediate filaments, and microtubules for structure and movement.

• DNA and RNA: DNA stores genetic information; RNA is involved in protein synthesis. Transcription is the process of making RNA from DNA; translation is the synthesis of proteins from RNA.

• Cell Cycle: Includes G1, S, G2 (interphase), and mitosis (cell division). Mitosis steps: prophase, metaphase, anaphase, telophase.

Tissues

Types and Characteristics of Tissues

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

• Epithelial Tissue: Covers surfaces, lines cavities, forms glands. Characteristics: tightly packed cells, avascular, high regeneration. Functions: protection, absorption, secretion, filtration.

• Connective Tissue: Supports, binds, and protects organs. Contains cells, fibers (collagen, elastic, reticular), and ground substance. Types include loose, dense, cartilage, bone, blood.

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

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

Epithelial Tissue Details

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

• Special Features: Cilia (movement), microvilli (absorption), goblet cells (mucus secretion).

• Functions: Protection, secretion, absorption, excretion.

Connective Tissue Details

• Extracellular Matrix: Composed of fibers and ground substance; provides strength and support.

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

• Functions: Support, protection, insulation, transport.

The Skeleton: Bones and Cartilage

Bone and Cartilage Structure and Function

The skeletal system provides support, protection, movement, mineral storage, and blood cell formation. Bones and cartilage are specialized connective tissues with distinct properties.

• Bone Cells: Osteoblasts (form bone), osteocytes (maintain bone), osteoclasts (break down bone).

• Cartilage Types: Hyaline (most common, flexible), elastic (flexible, ear), fibrocartilage (strong, intervertebral discs).

• Bone Structure: Compact (dense) and spongy (cancellous) bone. Periosteum covers bone; endosteum lines internal cavities.

• Bone Marrow: Red marrow (hematopoiesis), yellow marrow (fat storage).

• Bone Growth: Occurs at epiphyseal plates (growth plates) via endochondral ossification.

• Fracture Repair: Involves hematoma formation, fibrocartilaginous callus, bony callus, and bone remodeling.

• Bone Diseases: Osteoporosis (bone loss), osteomalacia/rickets (soft bones), Paget's disease (abnormal remodeling), osteosarcoma (bone cancer).

Fontanelles and Vertebral Curvatures

• Fontanelles: Soft spots on infant skulls that allow for growth. Anterior, posterior, sphenoidal, and mastoid fontanelles close at different times after birth.

• Vertebral Curvatures: Normal curves: cervical, thoracic, lumbar, sacral. Exaggerated curves: kyphosis (thoracic), lordosis (lumbar), scoliosis (lateral).

Paranasal Sinuses

• Sinuses: Air-filled spaces in skull bones (frontal, ethmoid, maxillary, sphenoid) that lighten the skull and enhance voice resonance.

Table: Comparison of Bone and Cartilage

Feature	Bone	Cartilage
Cells	Osteocytes, osteoblasts, osteoclasts	Chondrocytes, chondroblasts
Matrix	Hard, calcified (calcium phosphate)	Firm, flexible (chondroitin sulfate)
Blood Supply	Rich	Avascular
Growth	Appositional and interstitial	Mainly interstitial (in young), appositional (in mature)
Repair	Good	Poor

Key Equations and Concepts

• Osteon Structure: The functional unit of compact bone is the osteon (Haversian system).

• Bone Remodeling: Involves the balance between osteoblast and osteoclast activity.

• Calcium Homeostasis: Regulated by parathyroid hormone (PTH) and calcitonin.

• Example Equation:

$\text{Ca}^{2+} \text{ (bone)} \rightleftharpoons \text{Ca}^{2+} \text{ (blood)}$

Additional info: Some details, such as the specific names of all nine abdominal regions, the full list of organelles, and the precise steps of fracture repair, have been expanded for academic completeness.