Introduction to Anatomical Terms and Organ Systems

Anatomical Position and Planes/Sections

The anatomical position is a standardized posture used to describe locations and relationships of body parts. Anatomical planes are imaginary lines used to divide the body for study.

• Anatomical Position: Standing upright, facing forward, arms at sides, palms facing forward, feet together.

• Planes/Sections:

  • Sagittal Plane: Divides body into left and right parts.

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

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

• Example: A CT scan often uses the transverse plane to view cross-sections of the body.

Directional Terms

Directional terms describe the location of one body part relative to another.

• Superior/Inferior: Superior means above; inferior means below. Used for torso regions.

• Proximal/Distal: Proximal means closer to the point of attachment; distal means farther away. Used for limbs.

• Other Terms: Anterior (ventral), posterior (dorsal), medial, lateral, superficial, deep.

• Example: The knee is distal to the thigh but proximal to the ankle.

Regional Terms

Regional terms specify areas of the body, often used in medical and anatomical contexts.

• Examples: Brachial (arm), femoral (thigh), thoracic (chest), abdominal (abdomen).

• Application: Used to describe pain or injury location, e.g., "pain in the lumbar region" (lower back).

Body Cavities

Body cavities house internal organs and are divided into major and specific subdivisions.

• Dorsal Cavity: Contains cranial (brain) and vertebral (spinal cord) cavities.

• Ventral Cavity: Contains thoracic (heart, lungs) and abdominopelvic (digestive organs, bladder, reproductive organs) cavities.

• Most Specific Body Cavity: E.g., pericardial cavity (heart), pleural cavity (lungs).

• Example: The stomach is located in the abdominal cavity, a subdivision of the ventral cavity.

Serous Membranes

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

• Visceral Serosa: Covers organs.

• Parietal Serosa: Lines cavity walls.

• Specific Regions: Pleurae (lungs), pericardium (heart), peritoneum (abdominal organs).

• Example: The pericardium surrounds the heart, providing lubrication.

Organ Systems Overview

Organ systems are groups of organs working together for specific functions.

• Example: The digestive system includes the stomach and intestines; functions include nutrient breakdown and absorption.

• Key Point: Know two major functions and two major organs for each system.

Major Organs on Torso Models

Identification of organs and their associated systems is essential for lab exams.

• Example: The liver belongs to the digestive system; the heart to the cardiovascular system.

Histology: Epithelial, Connective, Muscle, and Nervous Tissues

Epithelial Tissues

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

• Types:

  1. Simple squamous epithelium: Single layer, flat cells. Locations: alveoli, blood vessels. Functions: diffusion, filtration.

  2. Simple cuboidal epithelium: Single layer, cube-shaped cells. Locations: kidney tubules, glands. Functions: secretion, absorption.

  3. Simple columnar epithelium: Single layer, tall cells. Locations: digestive tract, uterus. Functions: absorption, secretion.

  4. Pseudostratified ciliated columnar epithelium: Appears layered, but all cells touch basement membrane. Locations: trachea, upper respiratory tract. Functions: secretion, movement of mucus.

  5. Stratified squamous epithelium: Multiple layers, flat cells. Locations: skin, esophagus. Functions: protection against abrasion.

• Vascularity: Epithelial tissue is avascular (no blood vessels).

• Innervation: Epithelial tissue is innervated (has nerve supply).

• Key Terms: Apical surface (top), basal surface (bottom), cell shape, number of layers, nucleus, lumen, cilia, microvilli, basement membrane, goblet cells.

• Example: Microvilli in intestinal simple columnar epithelium increase surface area for absorption.

Connective Tissues

Connective tissues support, protect, and bind other tissues. They are classified as proper or specialized.

• Connective Tissue Proper:

  1. Loose areolar connective tissue

  2. Adipose connective tissue

  3. Reticular connective tissue

  4. Dense regular connective tissue

  5. Dense irregular connective tissue

  6. Elastic connective tissue

• Specialized Connective Tissue:

  1. Hyaline cartilage

  2. Elastic cartilage

  3. Fibrocartilage

  4. Bone

  5. Blood

• Locations & Functions: Know two major locations and functions for each type.

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

• Innervation: Most are innervated; cartilage is not.

• Cell Types:

  • Fibroblasts (proper), adipocytes (adipose), lymphocytes (reticular), chondrocytes (cartilage), osteocytes (bone), erythrocytes/leukocytes/thrombocytes (blood).

• Fiber Types:

  • Collagen: thick, strong, pink bands.

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

  • Reticular: thick, highly branched, dark strands.

• Ground Substance: Fills space between cells and fibers; in blood, called plasma.

• Cartilage Features: Lacunae (spaces housing chondrocytes).

• Bone Features: Osteon, central canal, lamella, osteocytes, lacuna, canaliculi.

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

• Example: Dense regular connective tissue forms tendons, providing strong attachment between muscle and bone.

Muscle Tissues

Muscle tissues are specialized for contraction and movement. There are three types.

• Skeletal Muscle: Voluntary, striated, multinucleated. Location: attached to bones.

• Cardiac Muscle: Involuntary, striated, single nucleus, intercalated discs. Location: heart.

• Smooth Muscle: Involuntary, non-striated, single nucleus. Location: walls of hollow organs (e.g., intestines, blood vessels).

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

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

• Example: Cardiac muscle contracts rhythmically to pump blood throughout the body.

Nervous Tissue

Nervous tissue is specialized for communication via electrical impulses.

• Cell Types: Neurons (cell body/soma, dendrites, axon hillock, axon, nucleus), neuroglia (supporting cells).

• Functions: Neurons transmit signals; neuroglia support and protect neurons.

• Example: Motor neurons stimulate muscle contraction.

Cell Cycle & Mitosis

Mitosis and Cytokinesis

Mitosis is the process of nuclear division, while cytokinesis is the division of the cytoplasm.

• Mitosis: Produces two genetically identical daughter cells.

• Cytokinesis: Splits the cytoplasm, completing cell division.

• Equation:

Sub-phases of Mitosis

Mitosis consists of several distinct phases, each with characteristic events.

• Interphase: Cell grows, DNA replicates (S phase).

• Prophase: Chromatin condenses, spindle forms.

• Metaphase: Chromosomes align at cell equator.

• Anaphase: Sister chromatids separate and move to poles.

• Telophase: Nuclear envelopes reform, chromosomes decondense.

• Cytokinesis: Cytoplasm divides, forming two cells.

• Example: Onion root tip slides show cells in various mitotic stages.

DNA Replication

DNA replication occurs during the S phase of interphase, ensuring each daughter cell receives a complete set of genetic material.

• Equation:

• Example: Before mitosis, each chromosome duplicates to form sister chromatids.

Identification of Mitotic Phases

Cells can be identified in different mitotic phases by their appearance under the microscope.

• Interphase: Nucleus visible, DNA uncondensed.

• Prophase: Chromosomes condense, spindle forms.

• Metaphase: Chromosomes aligned at center.

• Anaphase: Chromatids pulled apart.

• Telophase: Chromosomes at poles, nuclear envelope reforms.

• Cytokinesis: Cell membrane pinches, two cells form.

Summary Table: Tissue Types and Key Features

Additional info: This summary table is inferred for clarity and exam preparation.