Nail 5-26-26
Pernichium (Eponychium): Located at the cuticle. The cuticle does not always have to be flipped back.
Proximal Nail Hole (Proximal Fold): This is the skin surrounding the nail in the proximal area, situated right underneath the cuticle.
Lateral Folds: These are folds of skin surrounding the nail plate.
Distal Edge: The edge of the nail plate farthest from the root.
Lanula: The crescent-shaped area of the nail located right above the cuticle.
Nail Body (Nail Plate): The main visible part of the nail, which sits on top of the nail bed.
Nail Bed: The skin tissue underneath the nail plate.
Nail Matrix: Located underneath the roof of the nail; this is the area where the nail grows from.
Hypothelium (Hyponychium): Located beneath the distal edge of the nail plate when the hands are in the anatomical position.
Histology of the Integumentary System
Skin Layers: The epidermis consists of different layers.
Dermis and Hypodermis: Includes structures such as the dermal papilla, which anchors the epidermis to the dermis.
Visualization: * Anterior-Posterior (AP) Views. * Cross-Sectional Views: Always represent a transverse cut (often explained via X-ray).
Hair Follicles: Associated with adipose tissue. Histology allows for a detailed look at the cells making up each part of the hair follicle.
The Four Primary Tissue Types
Definition of Histology: The study of cells and the tissues they compose.
Epithelial Tissue: Found on surfaces; characterized by round edges and visible nuclei.
Connective Tissue: Described as looking like a "bag of cords" connected through a matrix.
Muscular Tissue: Found in the muscles; can be identified by the presence of striations (lines) that allow for contraction and relaxation.
Nervous Tissue: Found in the nerves; identified by unique extensions like dendrites and axons.
Epithelial Tissue Classifications
Cell Shapes: * Squamous: Flat cells. * Cuboidal: Cells shaped like cubes. * Columnar: Cells shaped like tall columns.
Layering Formats: * Simple: Consists of exactly one layer of cells. * Stratified: Consists of multiple layers of cells. * Pseudostratified: "Pseudo" means false. This tissue looks like it reflects multiple layers due to the staggered positioning of nuclei at different heights within the columns, but it is actually only one layer thick. Unlike simple columnar tissue where nuclei are aligned, pseudostratified nuclei are out of place (up and down).
Transitional Tissue: Cells that transition from one shape to another.
Non-keratinized Stratified Squamous: Layers of flat cells found in specific skin or mucosal areas.
Specific Structures: * External and Internal Membranes: Tissues may have spaces containing liquid for buoyancy and shock absorbency.
Connective Tissue Varieties
Areolar Tissue: A type of loose connective tissue.
Adipose Tissue: Fatty tissue.
Dense Irregular Tissue: Considered irregular because it lacks a specific pattern compared to adipose or areolar tissue.
Cartilage Varieties: * Hyaline Cartilage. * Elastic Cartilage: Flexible cartilage. * Fibrocartilage.
Bone Tissue: * Compact Bone: Compressed bone found on the outskirts (edges) of the bone. It provides the bone with its strength. It contains small perforations for blood vessels to lead to the outside. * Spongy Bone: Porous bone found just beneath the compact bone. It is lighter than compact bone, preventing the skeleton from being too heavy to move. It contains matrices where blood vessels run through.
Blood: Classified as a connective tissue.
Osteoporosis and Bone Density
Clinical Definition: A condition where bone density is lost. In the spongy bone, the gaps between blood vessel pathways become larger, weakening the bone and making it prone to fractures.
Demographics and Prevention: Women typically begin to lose bone density at approximately age .
Maintenance: * Weightlifting helps maintain density. * Adequate Vitamin D levels are required for calcium absorption. * Vitamin D with K2 is cited as more effective.
Visual Indicators: People may "bow over" or hunch due to the loss of density.
Blood Composition and Biology
Red Blood Cells (RBCs): These do not have a nucleus. Because they lack a nucleus, they do not contain DNA blueprints.
White Blood Cells (WBCs): These have a nucleus and are the source of DNA when blood is drawn. There are different types of WBCs. * Function: Act as a personal military, protecting against bacteria, viruses, parasites, and allergic reactions. * Monocytes: Large mass white blood cells associated with chronic conditions.
Platelets: Involved in clotting.
Bone Marrow: Blood is created in the marrow located in the medullary cavity deep within the bone. Bone marrow transplants require an extensive procedure to access this cavity.
Muscle Tissue Types
Skeletal Muscle: * Attached to bones. * Voluntary: Requires conscious thought to move. * Appearance: Distinctly striated (vertical lines).
Cardiac Muscle: * Exclusive to the heart. * Involuntary: Functions automatically without conscious thought. * Appearance: Lightly striated (striations are less dense and less prominent than skeletal muscle).
Smooth Muscle (Visceral Muscle): * Found in organs (ureters, esophagus, intestines) and vessels. * Involuntary: Moves things inside the body (e.g., peristaltic contractions moving food or urine). * Appearance: No striations at all.
Nervous Tissue Structure
Cell Body: The main part of the neuron.
Dendrites: Tree-branch-like extensions that act as "feelers" to carry sensory information into the cell.
Axon: The extension where sensory information travels down to connect to other nerve cells or organs.
Plexus: A network of millions of communicating nerve cells. The nervous system acts like an electrical system for the body; without innervation (power), muscles cannot move.
Questions & Discussion
Q: Can you explain that middle one again? Like, just the shape of it (referring to simple squamous cells)?A: These are flat cells. You will see simple squamous that looks like a cluster of flat cells in the middle. They are in the center, and the tissue includes an external and internal membrane with space for liquid to provide buoyancy and shock absorbency.
Q: When you say striations, you're talking about the light horizontal lines?A: No, the striations are actually the lines going vertically in the skeletal and cardiac muscle samples. They are very prominent in skeletal muscle and lightly present in cardiac muscle.
Q: If red blood cells don't have a nucleus, where do we get the DNA from when we draw blood?A: DNA is housed in the nucleus. All white blood cells have a nucleus, so that is where the DNA is obtained from.
Q: When we do the quiz or test for this particular section, will we be looking under the microscope at it, or will we have a diagram?A: You will be looking under the microscope and must be able to identify the tissues manually.