Lab #1: Histology Flashcards
Compound Light Microscope
Have two sets of magnifying lenses. Oculars and objectives.
Ocular Lenses
Or eyepieces. Brings the image into focus for the eye. 10x magnification.
Micrometer
Measuring skill in ocular lenses use to measure the height of the cells.
Objective Lenses
Ranges from 4x to 100x magnification. You change magnification rotating the Rotating Nosepiece.
Initially you should always view slide in 4x objective first, and progressively move higher up when you focus the image.
Stage
Platform on which the slide is placed.
Always secure the slide with the stage clip.
Coaxial Stage Control
Allows movement of the slide in the x and y plane.
Light Source
Illuminates the specimen. A dial on side of the scope controls the light intensity.
Diaphragm
Alters the light or contrast, controled by a thin lever beneath stage.
Coarse Focus
Controls height of the stage.
Fine Focus
Optimize or fine-tune the focus, especially when viewing through higher power objectives.
Interpupillary Distance
Distance between the oculars. Can be adjusted.
Parfocal
When you switch the objective lenses, the image should stay relatively in focus. But if you alter the coarse control, the focus will be lost.
Epithelia
Form the surface layer of the body, line body cavities, hollow organs and structures, and constitute most gland tissue. Any substance that enters or leaves the body must cross an epithelium.
Epithelia Structure
All consist on one or more layers of tightly packed cells, and little or no extracellular matrix between cells. Distinguishing features of an epithelium include a free apical surface and a fixed basal surface.
Specialized intracellular junctions join adjacent cells, and a thin basement membrane separates the basal surface from underlying connective tissue layers. Although epithelia lack blood vessels, many sensory nerve endings are present. Epithelia have a high regenerative capacity that allows them to maintain their function.
Epithelia Function
To resist dehydration and injury from physical, chemical, and biological agents; to selectively regulate materials entering and leaving the body; to secrete products produced by epithelial glands; and to monitor the environment through specialized sensory nerve endings and specialized epithelial cells.
Simple Epithelium
Epithelium composed of one layer of cells.
Stratified Epithelium
Epithelium composed of two or more layers of cells.
Squamous Epithelium
Epithelium where the apical cells are flat and thin.
Cuboidal Epithelium
Epithelium where the apical cells have a somewhat square shape.
Columnar Epithelium
Epithelium where the apical cells have a rectangular shape.
Transitional Epithelium
Found in the urinary tract, is a stratified epithelium that gives the impression of “transitioning” from cuboidal when the epithelium is relaxed to squamous when it is stretched.
Pseudostratified Epithelium
Found in the trachea for example. It’s a simple epithelium in which all cells contact the basal lamina but only some reach the apical surface. Cells are of varying heights and their nuclei are at different positions in the epithelium, giving the impression of stratification.
Ciliated or Nonciliated
Some epithelial classes have specializations of the free surface of apical cells. Simple columnar epithelial cells in some organs have cilia, which are small, fignerlike, motile projections. Thus, simple columnar epithelium is subclassified as ciliated or nonciliated.
Microvilli
In parts of the digestive and urinary tracts, epithelial cells involved in absorption have a dense collection of short cytoplasmic processes called microvilli on their free surface.
Microvilli are nonmotile and serve to increase surface area. Because the microvilli appear fuzzy in the light microscope, cells with numerous microvilli are said to have a brush border.
Keratinized or Nonkeratinized
A stratified epithelium has either dead or living cells as the surface layer. The dead cells contain the protein keratin. Therefore, stratified squamous epithelium is subclassified as keratinized or nonkeratinized.
Connective Tissue Functions
Its primary functions include structural support, binding structures together, fat storage, exchange of nutrients and metabolic waste, and defense and protection.
Connective Tissue Components
Share three basic components: cells, protein fibers, and ground substance. Together, the protein fibers and ground substance form the extracellular matrix. The proportions of these components, in addition to different cells and protein fibers, help define the various categories of connective tissue.
Connective Tissue Proper
Contains two subcategories: loose connective tissue and dense connective tissue.
Loose Connective Tissue
Has abundant ground substance with scattered cells and loosely arranged protein fibers.
Can be subdivided into areolar, adipose, and reticular connective tissue.
Dense Connective Tissue
Has abundant tightly packed fibers but relatively few cells and little ground substance.
Can be subdivided into: dense regular, dense irregular, and elastic connective tissue.
Areolar Connective Tissue
Found in the subcutaneous layer and around organs. It has a gel-like ground substance, numerous blood vessels, and scattered cells known as fibroblasts.
Adipose Connective Tissue
Found in subcutaneous tissue and around some organs. It is composed of closely-packed adipocytes (or fat cells).
Reticular Connective Tissue
Forms the stroma (a connective tissue framework) of lymph nodes, the spleen, the thymus, and bone marrow. It’s composed of a network of branched collagen fibers, known as reticular fibers, with scattered fibroblasts and leukocytes (or white blood cells) embedded in a gel-like ground substance.
Dense Regular Connective Tissue
Forms tendons and most ligaments. It’s composed of densely packed, parallel collagen fibers with fibroblasts between the layers. Little ground substance.
Dense Irregular Connective Tissue
Found in the dermis, periostrum, and perichondrium, and the capsule of organs. This tissue is composed predominantly of randomly arranged collagen fibers with fibroblasts interspersed. There’s more ground substance than found in dense regular connective tissue.
Elastic Connective Tissue
Found in walls of elastic arteries, the trachea and bronchi, and the vocal cords. This type of tissue is composed predominantly of branching elastic fibers, with fibroblasts in some spaces between the fibers.
Elastic fibers, formed by the protein elastin, stretch under tension and then return to their original shape when tension is released.
Supporting Connective Tissue
Can be subdivided into cartilage and bone.
Catilage
Has a semisolid extracellular matrix that allows flexibility.
Three types include hyaline, elastic, and fibrocartilage.
Bone
Has the solid matrix which is more regid and provides greater support.
Two types, compact and spongy.
Hyaline Cartilage
Most common type. Found on the articular surfaces of synovial joints; it also forms the cartilage of the larynx, trachea, and nose.
Chondrocytes (or mature catilage cells) are found within small spaces called lacunae that are scattered irregularly in the extracellular matrix. Collagen fibrils are present within the matrix but not visible in the light microscope. A perichondrium, a dense irregular connective tissue sheath, overlies most cartilage.
Elastic Cartilage
Found in the external ear and in the epiglottis. It contains abundant elastic fibers, which form a web-like mesh around lacunae that contain chondrocytes. Like hyaline cartilage, elastic cartilage usually has perichondrium.
Fibrocartilage
Found in intervertebral discs, the public symphysis, and the menisci of the knee joint. It contains nymerous irregular bundles of collagen fibers.
The sparse ground substance contains chondrocytes within lacunae that are frequently arranged in parallel rows. Unlike hyaline and elastic cartilage, fibrocartilage doesn’t have a perichondrium.
Compact Bone
Usually forms the hard, outer shell of bones. Concentric rings of bone called lamellae form cylindrical structures, known as osteons. Each osteon has a central canal that connects to a network of tiny branching passageways called canaliculi.
The central canal and canaliculi contain blood vessels. Osteocytes or mature bone cells occupy lacunae, small spaces between neighboring lamellae.
Spongy Bone
Also known as cancellous bone. Usually forms inside of bones. It does not contain osteons. Slender bony plates, called trabeculae, form a bony network.
The spaces between trabeculae contain bone marrow and blood vessels. Osteocytes are scattered throughout the trabeculae. The combination of compact and spongy bone allows bones to be both strong and lightweight.
Fluid Connective Tissue
Represented by blood.
Blood
The formed elements of blood specifically, its cells and cell fragments include erythrocytes (red blood cells), leukocytes (white blood cells), and platelets. The watery ground substance of blood contains dissolved protein fibers.
Muscle Tissue Function
Primary function is to produce movement of the skeleton or other tissues of the body. This results in body or organ movement, maintenance of posture, communication (such as facial expression and vocalization), control of body openings, and heat production.
Muscle Tissue Types
Skeletal, cardiac, and smooth.
Skeletal Muscle
Under voluntary control and is usually attached to bones via tendons or other connective tissues.
Cardiac Muscle
Found only in walls of heart and is under involuntary control. Cardiac muscle fibers are short, branched cells with one or two centrally located nuclei and numerous mitochondria. These fibers exhibit striations and banding patterns similar to those seen in skeletal muscle fibers.
Intercalated Discs
Cell junctions that are unique to cardiac muscle. Two specializations within these junctions link cardiac muscle fibers both electrically and mechanically.
Smooth Muscle
Located in the wall of blood vessels, ducts, and organs and is under involuntary control.
They’re elongated, with tapered ends (fusiform-shaped), and contain a single, centrally-located nucleus. The myofilaments are not arranged in any specific pattern and, therefore, do not produce visible striations of form sacromeres.
Epidermis
Outermost layer of the skin. Composed of kerantinized stratified squamous epithelial tissue.
Dermis
Below the epidermis. Composed of dense irregular connective tissue.
Hypothermis
Or subcutaenous tissue. Composed primarily of loose connective tissue such as adipose and areolar tissues.
