Anatomy & Physiology: Foundational Concepts, Cell Structure, Tissues, and Integumentary System

Anatomical Position and Directional Terminology

Introduction

Understanding anatomical position and directional terminology is essential for accurately describing locations and relationships of body parts in Anatomy & Physiology.

• Anatomical Position: The standard reference position for the body in the study of anatomy. The body stands upright, facing forward, arms at the sides with palms facing forward, and feet parallel.

• Directional Terminology: Terms used to describe the locations of structures relative to other structures or locations in the body.

  • Inferior/Superior: Below/Above

  • Anterior (Ventral)/Posterior (Dorsal): Front/Back

  • Proximal/Distal: Closer to/Farther from the point of attachment

  • Medial/Lateral: Toward the midline/Away from the midline

  • Superficial/Deep: Toward the surface/Away from the surface

Planes of Section

Introduction

Body planes are imaginary lines used to divide the body into sections for anatomical study and medical imaging.

• Sagittal and Parasagittal Plane: Divides the body into right and left portions. The midsagittal plane divides the body into equal right and left halves.

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

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

• Oblique Plane: Passes through the body at an angle between the horizontal and vertical planes.

Abdominal and Serous Membranes

Abdominal Regions

The abdomen is divided into nine regions to help locate organs and describe pain or injury.

• Serous Membranes: Thin membranes lining the thoracic and abdominopelvic cavities, reducing friction between organs.

  • Visceral Membrane: Covers the organs.

  • Parietal Membrane: Lines the cavity walls.

Cell Structure and Organelles

Introduction

Cells are the basic structural and functional units of life. Their structure is organized to support various physiological functions.

• Phospholipid Bilayer and Fluid Mosaic Model: The cell membrane is composed of a double layer of phospholipids with embedded proteins, allowing selective permeability and fluidity.

• Membrane Transport Mechanisms:

  • Simple Diffusion: Movement of molecules from high to low concentration without energy input.

  • Osmosis: Diffusion of water across a selectively permeable membrane.

  • Facilitated Diffusion: Movement of molecules via membrane proteins, still down the concentration gradient.

  • Active Transport: Movement of substances against their concentration gradient using energy (ATP).

  • Endocytosis/Exocytosis: Bulk transport of materials into (endocytosis) or out of (exocytosis) the cell via vesicles.

• Organelles:

  • Ribosomes: Sites of protein synthesis.

  • Rough and Smooth Endoplasmic Reticulum (ER): Rough ER synthesizes proteins; smooth ER synthesizes lipids and detoxifies chemicals.

  • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.

  • Lysosomes: Contain digestive enzymes to break down waste.

  • Mitochondria: Powerhouse of the cell; site of ATP production.

  • Peroxisomes: Break down fatty acids and detoxify harmful substances.

  • Cytoskeleton: Microfilaments, intermediate filaments, and microtubules provide structural support and facilitate movement.

  • Centrioles: Involved in cell division.

  • Nucleus and Nucleolus: Nucleus contains genetic material; nucleolus synthesizes ribosomal RNA.

Mitosis and Meiosis

Cell Cycle and Division

Cell division is essential for growth, repair, and reproduction. Mitosis and meiosis are two types of cell division with distinct outcomes.

• Cell Cycle Phases: Interphase (G1, S, G2), Prophase, Metaphase, Anaphase, Telophase, Cytokinesis.

• Mitosis: Produces two genetically identical diploid cells for growth and repair.

• Meiosis: Produces four genetically unique haploid cells (gametes) for sexual reproduction.

• Haploid vs Diploid Cells: Haploid cells (n) have one set of chromosomes; diploid cells (2n) have two sets.

Tissues

Introduction

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

• Epithelial Tissues: Cover body surfaces and line cavities.

  • Simple Epithelium: Single cell layer (squamous, cuboidal, columnar, pseudostratified ciliated).

  • Stratified Epithelium: Multiple cell layers (squamous, cuboidal, columnar, transitional).

• Connective Tissues: Support, bind, and protect other tissues.

  • Loose: Areolar, reticular, adipose.

  • Dense: Regular, irregular, elastic.

  • Cartilage: Hyaline, elastic, fibrocartilage.

  • Bone: Osseous tissue.

  • Blood: Fluid connective tissue.

• Muscle Tissue: Responsible for movement.

  • Skeletal: Voluntary, striated.

  • Cardiac: Involuntary, striated, found in heart.

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

• Nervous Tissue: Conducts electrical impulses.

  • Neuron: Main signaling cell.

  • Neuroglial: Support and protect neurons.

Integumentary System

Functions and Structure

The integumentary system includes the skin and its accessory structures, providing protection, sensation, and regulation.

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

• Layers of Skin:

  • Epidermis: Outermost layer; contains various cell types with specific functions.

  • Dermis: Middle layer; contains connective tissue, blood vessels, nerves, and appendages.

  • Subcutaneous (Hypodermis): Deepest layer; stores fat and anchors skin.

• Accessory Structures:

  • Oil (Sebaceous) Glands: Secrete sebum; associated with blackheads, whiteheads, pimples.

  • Sweat Glands: Eccrine (widespread, thermoregulation) vs Apocrine (axillary, groin, emotional sweating).

  • Hair: Provides protection, sensation; differences between vellus (fine) and terminal (thick) hair; balding.

  • Nails: Structure and function; protect fingertips and enhance sensation.

Additional info:

• Table: Comparison of Epithelial Tissue Types

Type	Layers	Shape	Location	Function
Simple Squamous	1	Flat	Alveoli, blood vessels	Diffusion, filtration
Simple Cuboidal	1	Cube	Kidney tubules, glands	Secretion, absorption
Stratified Squamous	Multiple	Flat	Skin, mouth, esophagus	Protection
Transitional	Multiple	Variable	Urinary bladder	Stretching

• Example: The stratified squamous epithelium of the skin provides a barrier to pathogens and prevents water loss.