Introduction to Anatomical Terms and Organ Systems

Anatomical Position and Planes/Sections

The anatomical position is a standardized posture used to describe the locations and relationships of body parts. Understanding anatomical planes and sections is essential for describing cuts or views of the body.

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

• Planes/Sections:

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

  • Sagittal Plane: Divides the body into right and left parts. The midsagittal (median) plane divides it into equal halves.

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

  • Oblique Section: Cuts made diagonally between horizontal and vertical planes.

Directional Terms

Directional terms describe the positions of structures relative to other structures or locations in the body.

• Superior/Inferior: Toward the head/away from the head (used for torso).

• Anterior (Ventral)/Posterior (Dorsal): Toward the front/back of the body.

• Medial/Lateral: Toward the midline/away from the midline.

• Proximal/Distal: Closer to/farther from the point of attachment (used for limbs).

• Superficial/Deep: Toward/away from the body surface.

Regional Terms

Regional terms specify particular areas within major body divisions.

• Axial Region: Head, neck, and trunk.

• Appendicular Region: Limbs (arms and legs).

• Examples: Brachial (arm), Femoral (thigh), Thoracic (chest), Abdominal (abdomen).

Body Cavities

The body contains several cavities that house and protect organs. Each cavity may have subdivisions.

• Dorsal Body Cavity:

  • Cranial Cavity: Contains the brain.

  • Vertebral (Spinal) Cavity: Contains the spinal cord.

• Ventral Body Cavity:

  • Thoracic Cavity: Contains heart and lungs.

    • Pleural Cavities: Each surrounds a lung.

    • Mediastinum: Contains the pericardial cavity (heart) and other thoracic organs.

  • Abdominopelvic Cavity:

    • Abdominal Cavity: Contains digestive organs, spleen, kidneys.

    • Pelvic Cavity: Contains bladder, reproductive organs, rectum.

Most specific body cavity refers to the smallest subdivision that contains a particular organ (e.g., the pericardial cavity for the heart).

Serous Membranes

Serous membranes line body cavities and cover organs, reducing friction.

• Visceral Serosa: Covers organs.

• Parietal Serosa: Lines cavity walls.

• Pleurae: Lungs.

• Pericardium: Heart.

• Peritoneum: Abdominopelvic organs.

Organ Systems Overview

The human body is organized into organ systems, each with specific functions and major organs.

• Example: Digestive System

  • Functions: Breaks down food, absorbs nutrients.

  • Major Organs: Stomach, intestines.

• Be able to identify organs on torso models and assign them to their respective organ systems.

Histology: Tissues of the Human Body

Epithelial Tissue

Epithelial tissues cover body surfaces, line cavities, and form glands. They are classified by cell shape and number of layers.

• Characteristics: Avascular (no blood vessels), innervated (has nerves), high regenerative capacity.

• Surfaces:

  • Apical Surface: Exposed to exterior or cavity.

  • Basal Surface: Attached to underlying connective tissue.

• Basement Membrane: Supports epithelium, separates it from connective tissue.

Types of Epithelial Tissue

• Simple Squamous Epithelium

  • Structure: Single layer of flat cells.

  • Locations: Air sacs of lungs, lining of blood vessels.

  • Functions: Diffusion, filtration.

• Simple Cuboidal Epithelium

  • Structure: Single layer of cube-shaped cells.

  • Locations: Kidney tubules, glands.

  • Functions: Secretion, absorption.

• Simple Columnar Epithelium

  • Structure: Single layer of tall, column-like cells.

  • Locations: Lining of digestive tract, uterine tubes.

  • Functions: Absorption, secretion of mucus and enzymes.

• Pseudostratified Ciliated Columnar Epithelium

  • Structure: Appears multilayered but all cells touch the basement membrane; often ciliated.

  • Locations: Trachea, upper respiratory tract.

  • Functions: Secretion, movement of mucus by cilia.

• Stratified Squamous Epithelium

  • Structure: Multiple layers; surface cells are flat.

  • Locations: Skin (keratinized), mouth, esophagus (non-keratinized).

  • Functions: Protection against abrasion.

Additional Terms: Nucleus, lumen (space inside a tube), cilia (hair-like projections), microvilli (increase surface area), goblet cells (mucus-producing), basement membrane.

Connective Tissue

Connective tissues support, bind, and protect other tissues and organs. They have varying degrees of vascularity and contain specialized cells and extracellular matrix (fibers and ground substance).

• Are all connective tissues vascular? Most are, but cartilage is avascular.

• Are all connective tissues innervated? Most are, but cartilage is not.

Types of Connective Tissue

• Connective Tissue Proper

  • Loose Areolar Connective Tissue: Wraps and cushions organs; found under epithelia.

  • Adipose Connective Tissue: Stores fat; found under skin, around kidneys.

  • Reticular Connective Tissue: Forms stroma of lymphoid organs; found in lymph nodes, spleen.

  • Dense Regular Connective Tissue: Parallel collagen fibers; found in tendons, ligaments.

  • Dense Irregular Connective Tissue: Irregularly arranged fibers; found in dermis of skin.

  • Elastic Connective Tissue: High proportion of elastic fibers; found in walls of large arteries.

• Specialized Connective Tissue

  • Hyaline Cartilage: Supports, reinforces; found in nose, trachea, ends of long bones.

  • Elastic Cartilage: Maintains shape, flexibility; found in external ear.

  • Fibrocartilage: Absorbs shock; found in intervertebral discs.

  • Bone (Osseous Tissue): Supports, protects, stores minerals; found in bones.

  • Blood: Transports gases, nutrients, wastes; found in blood vessels.

Cell Types in Connective Tissue

• Fibroblasts: Produce fibers in connective tissue proper.

• Adipocytes: Store fat in adipose tissue.

• Lymphocytes: Found in reticular tissue.

• Chondrocytes: Found in cartilage, located in lacunae.

• Osteocytes: Found in bone, located in lacunae.

• Erythrocytes (RBCs), Leukocytes (WBCs), Thrombocytes (Platelets): Found in blood.

Fiber Types in Connective Tissue

• Collagen Fibers: Thick, strong, provide tensile strength.

• Elastic Fibers: Thin, stretchable, provide elasticity.

• Reticular Fibers: Short, branched, form supportive networks.

Additional Features

• Ground Substance: Amorphous material filling space between cells and fibers.

• Lacuna: Small cavity housing chondrocytes or osteocytes.

• Bone Tissue Features:

  • Osteon: Structural unit of compact bone.

  • Central Canal: Contains blood vessels and nerves.

  • Lamella: Concentric rings of bone matrix.

  • Canaliculi: Tiny canals connecting osteocytes.

• Blood: Plasma is the ground substance; specialized cells include erythrocytes, leukocytes, and platelets.

Muscle Tissue

Muscle tissue is specialized for contraction and movement. There are three types, each with unique features.

• Skeletal Muscle Tissue:

  • Structure: Long, cylindrical, multinucleate, striated.

  • Control: Voluntary.

  • Location: Attached to bones.

• Cardiac Muscle Tissue:

  • Structure: Branched, striated, usually one nucleus per cell, intercalated discs present.

  • Control: Involuntary.

  • Location: Heart wall.

• Smooth Muscle Tissue:

  • Structure: Spindle-shaped, non-striated, single nucleus.

  • Control: Involuntary.

  • Location: Walls of hollow organs (e.g., intestines, blood vessels).

  • Longitudinal vs. Circular: Refers to orientation of fibers in organ walls.

Additional Features: Nuclei, striations (skeletal and cardiac), intercalated discs (cardiac only).

Nervous Tissue

Nervous tissue is specialized for communication via electrical and chemical signals. It consists of neurons and supporting cells (neuroglia).

• Neuron Structure:

  • Cell Body (Soma): Contains nucleus and organelles.

  • Dendrites: Receive signals.

  • Axon Hillock: Region where axon originates.

  • Axon: Transmits signals away from cell body.

  • Neuroglia: Support, protect, and nourish neurons.

Cell Cycle & Mitosis

Overview of Mitosis and Cytokinesis

The cell cycle is the series of events that cells go through as they grow and divide. Mitosis is the process of nuclear division, while cytokinesis is the division of the cytoplasm.

• Mitosis: Division of the nucleus to produce two genetically identical daughter cells.

• Cytokinesis: Division of the cytoplasm, usually follows mitosis.

Phases of the Cell Cycle

• Interphase: Period of cell growth and DNA replication.

  • G1 Phase: Cell growth.

  • S Phase: DNA replication occurs.

  • G2 Phase: Preparation for mitosis.

• Mitosis: Divided into sub-phases:

  • Prophase: Chromatin condenses into chromosomes; nuclear envelope breaks down; spindle forms.

  • Metaphase: Chromosomes align at the cell's equator (metaphase plate).

  • Anaphase: Sister chromatids separate and move toward opposite poles.

  • Telophase: Chromosomes decondense; nuclear envelopes reform.

  • Cytokinesis: Cytoplasm divides, forming two daughter cells.

Identification of Cell Cycle Stages

Onion root tip slides are commonly used to observe cells in various stages of the cell cycle.

• Interphase: Nucleus visible, DNA not condensed.

• Prophase: Chromosomes become visible, nuclear envelope disappears.

• Metaphase: Chromosomes line up at the center.

• Anaphase: Chromatids pulled apart to opposite poles.

• Telophase: Chromosomes at poles, nuclear envelope reforms.

• Cytokinesis: Cytoplasm divides, two cells form.

Summary Table: Major Tissue Types and Features

Additional info: For all tissue types, be able to identify key features and cell types on microscope slides, as well as understand their functional significance in the human body.