Body Planes
Introduction to Medical Imaging and Cross-Sectional Orientations
3D World: Humans live in a three-dimensional world necessitating imaging from three planes.
Importance: Understanding these planes is crucial for interpreting medical images like X-rays, CT scans, and MRIs.
Main Planes: Frontal, sagittal, transverse.
Cross Section: A view from a cut that reveals internal structures.
The Frontal (Coronal) Plane
Definition: Divides body into anterior (front) and posterior (back) halves.
Alternative Name: Coronal plane.
Visual Characteristics: Shows an outline of the body from the front.
Examples:
Frontal X-ray of Spinal Fusion: Displays medical hardware used in surgeries.
Personal Anecdote: The speaker has 4 screws from spinal fusion.
Frontal CT Scan: Illustrates vertebrae, pelvis, femurs from a forward perspective.
Color Indicators:
Anterior (front) is blue in diagrams.
Posterior (back) is green in diagrams.
Sagittal Plane- divides the body into left and right portions
Midsagittal Plane- divides the body exactly in the middle
Frontal/ Coronal Plane- separates the body from the front and back
Transverse/ Horizontal Plane- divides the body from the top and bottom
The Sagittal Plane
Definition: Divides body into left and right sections.
Memory Aid: Both "side" and "sagittal" start with "S."
Sub-classifications:
Midsagittal Plane: Division down the midline for equal left and right halves.
Regular Sagittal Plane: Off-center cuts not at midline.
Indicators:
Midsagittal shows the spinal cord in the center.
Regular sagittal does not show spinal cord.
Examples:
CT Scan (Midsagittal): Shows spinal cord and internal organs side view.
CT Scan (Regular Sagittal): Shows side view without spinal cord.
Sagittal MRI of the Brain: Displays brain's internal structures laterally.
The Transverse Plane
Definition: Cuts horizontally, dividing the body into superior (top) and inferior (bottom) parts.
Visual Characteristics: Appears as a horizontal slice, not resembling typical human outline.
Examples:
Transverse Cross Section of the Leg: Reveals internal layering of skin, muscle, and bone.
Transverse MRI of the Brain: Shows brain symmetry from an above or below view.
Color Indicators:
Superior (top) is red in diagrams.
Inferior (bottom) is orange in diagrams.
Summary Recap and Knowledge Test
Frontal Plane: Divides into front and back.
Sagittal Plane: Divides into left and right; spinal cord present indicates midsagittal.
Transverse Plane: Horizontal cut for top and bottom sections.
Knowledge Check Scenarios:
Scenario 1: A scan of lungs and heart with no human outline = transverse section.
Scenario 2: A scan showing lungs and heart from the front = frontal section.
Scenario 3: A side view of the spine = sagittal section (midsagittal if central).
Body Cavities
Dorsal Cavity:
Contains the Cranial Cavity: Houses the brain.
Contains the Vertebral Cavity: Houses the spinal cord.
Example: Think of the dorsal cavity like a protective case that holds your head and spine.
Ventral Cavity:
Contains the Thoracic Cavity: Holds the heart and lungs.
Contains the Abdominopelvic Cavity: Encompasses the abdomen (digestive organs) and pelvic region (reproductive organs).
Example: The ventral cavity acts like your torso, protecting essential organs.
Primary Tissues: Groups of cells with similar functions. There are four types of tissues:
Epithelial Tissue:
Covers the exterior of organs and structures.
Can consist of a single layer (simple) or multiple layers (stratified) of cells.
Example: Skin is made up of epithelial tissue, protecting us from the outside.
Connective Tissue:
Composed of a matrix that includes both living and nonliving substances.
Provides structure and support to the body.
Example: Bone and adipose (fat) tissue are types of connective tissue.
Muscle Tissue:
Three main types:
Smooth Muscle: Involuntary muscle found in organs (e.g., intestines).
Cardiac Muscle: Involuntary muscle that makes up the heart.
Skeletal Muscle: Voluntary muscle that moves bones.
Example: Your bicep is made of skeletal muscle, which you can control.
Nervous Tissue:
Made of specialized cells called neurons that conduct electrical impulses.
Function: Transmits signals throughout the body to coordinate actions.
Example: The brain is made of nervous tissue, responsible for processing information.
Introduction to Human Body Cavities
The human body is divided into two main cavities:
Dorsal cavity: Located at the back of the body.
Ventral cavity: Located at the front.
A cavity is a fluid-filled space containing various organs.
The Dorsal Cavity
Located toward the posterior (back) of the body.
Contains two primary components of the central nervous system:
Brain: Protected by the skull.
Spinal cord: Surrounded by the vertebrae.
Sub-cavities of the dorsal cavity:
Cranial Cavity: Space within the skull for the brain.
Spinal Cavity: Located just below the cranial cavity; it houses the spinal cord.
The spinal cord conducts signals between the brain and the body.
The Ventral Cavity
Located toward the anterior (front) of the body.
Contains various organs including the heart, lungs, and digestive organs.
Subdivided into two main sub-cavities:
Thoracic cavity: Contains lungs, heart, etc.
Abdominopelvic cavity: Contains digestive organs, urinary organs, and reproductive organs.
Subdivisions of the Thoracic Cavity
Thoracic cavity: The superior part of the ventral cavity.
Specific sub-cavities within the thoracic cavity:
Pleural Cavities: Each lung is housed here.
Pericardial Cavity: Houses the heart, protected by the pericardial membrane (meaning 'around the heart').
Mediastinum: Central part of the thoracic cavity; contains the pericardial cavity, trachea, aorta, and esophagus.
The Abdominopelvic Cavity
Below the thoracic cavity is the abdominal cavity, containing the stomach and other digestive organs.
Diaphragm: A muscle separating the thoracic cavity from the abdominal cavity.
Pelvic Cavity: Found below the abdominal cavity; contains urinary organs and reproductive organs.
Abdominal and pelvic regions are often combined into the abdominopelvic cavity due to the lack of a distinct physical separation.
Classroom Demonstration: Terry the Torso Model
Terry the Torso helps visualize organ placement.
Thoracic Organs:
Lungs: Located in pleural cavities.
Heart: Found in the pericardial cavity within the mediastinum.
Trachea: Located posterior to the heart.
Esophagus: Also posterior to the heart.
Aorta: Major blood vessel carrying blood from the heart.
Abdominopelvic Organs:
Pelvic Region: Urinary bladder and reproductive organs.
Abdominal Region: Contains the kidneys, pancreas, spleen, and other digestive organs.
The diaphragm separates thoracic and abdominal cavities.
BIOS 1300 Lab: The Skin Model
Skin is divided into three primary regions:
Epidermis (top layer).
Dermis (middle region).
Hypodermis (bottom layer).
Histological Layers of the Epidermis
The epidermis has five distinct strata:
Stratum corneum: Outermost layer.
Stratum lucidum: Below corneum.
Stratum granulosum.
Stratum spinosum.
Stratum basale: Deepest layer.
Dermal papillae: Projections from the dermis.
Epidermal ridges: Downward-facing ridges fitting with dermal papillae.
Regions and Structures of the Dermis
The dermis includes:
Papillary region: Top half of the dermis.
Reticular layer: Bottom half.
Skin appendages in the dermis:
Sebaceous glands: Oil glands around hair follicles.
Erector pili muscle: Causes goosebumps by pulling hair follicles upright.
Sweat glands: Indicated in the model with green and white colors.
Vasculature and Sensory Receptors
Vasculature in the Dermis:
Veins: Blue color.
Arteries: Red color; oxygenated blood.
Nerves: Yellow color.
Specialized sensory receptors:
Fascidians corpuscles: Detect deep pressure.
Meissner's corpuscles: Detect light touch.
Merkel's disc: Also detects light touch; has bulbs on nerve ends.
Free nerve endings: Detect pain and temperature without bulbs.
The Hypodermis
The hypodermis is the deepest layer of the skin.
Contains adipose tissue (yellow fatty tissue).
Questions & Discussion
Question: How can one distinguish between Merkel's discs and free nerve endings?
Response: Merkel's discs have visible bulbs, while free nerve endings do not.
Fun Fact: "Terry the Torso" has a metal latch to hold organs together!
Overview of Body Tissues
Four Major Types: Nervous, Muscle, Epithelial, Connective
Functionality: Each tissue type interacts and performs specialized functions to form organs.
Nervous Tissue
Components:
Neurons:
Highly irritable and responsive; carry impulses along their processes.
Location: Found throughout the nervous system based on function.
Characteristics: Ametotic (do not divide).
Neuroglia Cells (Glial Cells):
Support and protect neurons; assist in communication.
Functions: Insulation of nerve fibers, binding nerve tissue, supporting neuron health, supplying nutrients, and performing phagocytosis.
Characteristics: Mitotic (can divide) and outnumber neurons significantly.
Example: Multipolar neuron illustrating parts such as dendrites, axon, and cell body.
Epithelial Tissue
General Characteristics:
Forms the lining of body surfaces and cavities.
Composed of closely packed cells joined by desmosomes.
Lacks blood vessels; relies on diffusion from underlying tissues for nutrients.
Underlying layer called the Basement Membrane helps adhere tissues.
Mitosis: Provides new cells to replace older, worn-out cells.
Cell Layers:
Simple: A single layer of cells.
Stratified: Two or more layers of cells.
Pseudostratified: Appears multilayered but is one layer with varying cell heights.
Transitional: Layer changes with lumen content, found in the urinary bladder.
Cell Shapes:
Squamous: Flat, scale-like cells.
Cuboidal: Short, cube-like cells, involved in secretion.
Columnar: Elongated cells that can have specialized functions (e.g., with cilia).
Types of Epithelial Tissue:
Simple Squamous:
Structure: One layer of flat cells.
Examples: Air sacs in lungs and walls of capillaries; allows quick diffusion.
Cuboidal Epithelium:
Types: Simple and stratified.
Examples: Ducts of salivary glands and kidney tubules; involved in secretion.
Simple Columnar Epithelium:
May have goblet cells for mucus production.
Examples: Lining of the small intestine (with microvilli for absorption) and fallopian tubes (with cilia to move eggs).
Pseudostratified Columnar Epithelium:
Appears layered but has a single layer with all cells reaching the basement; ciliated.
Example: Lining of respiratory tubes, contains goblet cells producing mucus and cilia moving debris out.
Stratified Squamous Epithelium:
Thickest epithelium; outer cells are flattened.
Types:
Keratinized: Contains keratin, found in outer skin; provides waterproofing.
Non-Keratinized: Lacks keratin, found in oral cavity and esophagus; provides protection against abrasion.
Transitional Epithelium:
Specialized lining of the urinary bladder; allows for stretching.
Functionality: Changes shape with varying levels of urine.
Conclusion
Understanding the structure and functions of nervous and epithelial tissues is essential for recognizing how they contribute to the overall functionality of organs and systems in the body.