Introduction to Anatomical Terms and Organ Systems

Anatomical Position and Planes/Sections

The anatomical position is a standardized stance used to describe locations and directions on the human body. Understanding anatomical planes and sections is essential for interpreting medical images and anatomical diagrams.

• 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) portions.

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

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

  • Oblique Plane: Passes through the body at an angle.

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 the 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 and specific organs.

• Dorsal Body Cavity:

  • Cranial Cavity: Contains the brain.

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

• Ventral Body Cavity:

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

  • Abdominopelvic Cavity: Contains digestive, urinary, and reproductive organs; subdivided into abdominal and pelvic cavities.

Most specific body cavity: For example, the heart is in the pericardial cavity, which is within the mediastinum, within the thoracic cavity, within the ventral body cavity.

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

  • Major Functions: Breaks down food, absorbs nutrients.

  • Major Locations: Stomach, intestines.

• Example: Respiratory System

  • Major Functions: Gas exchange, supplies oxygen to blood.

  • Major Locations: Lungs, trachea.

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.

• Simple Squamous Epithelium:

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

  • Functions: Diffusion, filtration.

• Simple Cuboidal Epithelium:

  • Locations: Kidney tubules, glands.

  • Functions: Secretion, absorption.

• Simple Columnar Epithelium:

  • Locations: Digestive tract lining, uterine tubes.

  • Functions: Absorption, secretion of mucus and enzymes.

• Pseudostratified Ciliated Columnar Epithelium:

  • Locations: Trachea, upper respiratory tract.

  • Functions: Secretion, movement of mucus by cilia.

• Stratified Squamous Epithelium:

  • Locations: Skin (epidermis), lining of mouth and esophagus.

  • Functions: Protection against abrasion.

• Key Features:

  • Avascular: Epithelial tissues lack blood vessels.

  • Innervated: They have nerve supply.

  • Apical Surface: Exposed to exterior or cavity.

  • Basal Surface: Attached to underlying connective tissue.

  • Basement Membrane: Supports epithelium.

  • Cell Shape: Squamous (flat), cuboidal (cube-shaped), columnar (tall).

  • Number of Layers: Simple (one layer), stratified (multiple layers).

  • Special Structures: Cilia (movement), microvilli (absorption), goblet cells (mucus production), lumen (cavity), nucleus location.

Connective Tissue

Connective tissues support, bind, and protect other tissues and organs. They vary in structure and function.

• Connective Tissue Proper:

  • Loose Areolar: Under epithelia; cushions organs, inflammation.

  • Adipose: Under skin, around organs; stores fat, insulates, protects.

  • Reticular: Lymphoid organs; supports other cells.

  • Dense Regular: Tendons, ligaments; attaches muscles to bones, withstands tension.

  • Dense Irregular: Dermis of skin; structural strength.

  • Elastic: Walls of large arteries; allows recoil after stretching.

• Specialized Connective Tissue:

  • Hyaline Cartilage: Ends of long bones, nose; supports, cushions.

  • Elastic Cartilage: Ear, epiglottis; maintains shape, flexibility.

  • Fibrocartilage: Intervertebral discs; absorbs shock.

  • Bone: Bones; supports, protects, stores minerals.

  • Blood: Within blood vessels; transports gases, nutrients, wastes.

• Vascularity: Most connective tissues are vascular (except cartilage).

• Innervation: Most are innervated (except cartilage).

• Cell Types:

  • Fibroblasts: Connective tissue proper.

  • Adipocytes: Adipose tissue.

  • Lymphocytes: Reticular tissue.

  • Chondrocytes: Cartilage (in lacunae).

  • Osteocytes: Bone.

  • Erythrocytes, Leukocytes, Thrombocytes: Blood cells.

• Fiber Types:

  • Collagen: Thick, strong, pink bands.

  • Elastic: Thin, dark, hair-like strands.

  • Reticular: Thick, branched, dark fibers.

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

• Cartilage Features: Lacunae (spaces housing chondrocytes).

• Bone Features:

  • Osteon: Structural unit.

  • Central Canal: Contains blood vessels/nerves.

  • Lamella: Concentric rings of matrix.

  • Osteocytes: Mature bone cells.

  • Lacuna: Small cavities for osteocytes.

  • Canaliculi: Tiny canals connecting osteocytes.

• Blood Features: Plasma (liquid matrix), erythrocytes (RBCs), leukocytes (WBCs), thrombocytes (platelets).

Muscle Tissue

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

• Skeletal Muscle:

  • Striated, voluntary.

  • Multiple nuclei per cell.

  • Location: Attached to bones.

• Cardiac Muscle:

  • Striated, involuntary.

  • Intercalated discs present.

  • Location: Heart wall.

• Smooth Muscle:

  • Non-striated, involuntary.

  • Single, central nucleus.

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

  • Longitudinal and circular layers: Allow peristalsis in organs.

• Key Features: Nuclei, striations (skeletal/cardiac), intercalated discs (cardiac).

Nervous Tissue

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

• Neuron: Main cell type; transmits impulses.

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

• Dendrites: Receive signals.

• Axon Hillock: Region where axon originates.

• Axon: Conducts impulses away from cell body.

• Neuroglia: Support, protect, and nourish neurons.

• Nucleus: Found in both neurons and neuroglia.

Cell Cycle and 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 grows, organelles duplicate.

  • S Phase: DNA replication occurs.

  • G2 Phase: Final preparations for division.

• Mitosis Sub-phases:

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

  • Metaphase: Chromosomes align at the cell's equator.

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

  • Telophase: Chromosomes decondense; nuclear envelopes reform.

  • Cytokinesis: Cytoplasm divides, forming two 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 metaphase plate.

• Anaphase: Chromatids pulled apart to opposite poles.

• Telophase: Chromosomes at poles, nuclear envelope reforms.

• Cytokinesis: Cell membrane pinches, two daughter cells form.

Major Events in Each Phase

• Interphase: DNA replicates during S phase.

• Prophase: Chromosomes condense, spindle forms.

• Metaphase: Chromosomes align at the center.

• Anaphase: Sister chromatids separate.

• Telophase: Nuclear envelopes reform, chromosomes decondense.

• Cytokinesis: Cytoplasm divides, resulting in two cells.

Summary Table: Tissue Types and Key Features

Additional info: This guide expands on the study guide outline by providing definitions, examples, and context for each tissue and organ system, as well as a summary table for quick review. For lab practicals, be able to visually identify tissues and structures on slides and models.