Chapter 4 - Tissue Flashcards
Tissue
Groups of cells that are similar in structure and perform a similar or related function
Epithelial Tissue
sheet of cells that covers a body surface; or lines a body cavity; found in the body:
- Covering and lining
- As glandular epithelial (makes up glands). Typically found in GI gastinual intestine tract (mouth all the way to the anus, inside the thorax, in the abdomen, and on our skin)
Epithelial General Functions
- Protection undying tissue from mechanical injury, harmful chemicals, pathogens, and from excessive water loss.
- Sensory stimuli are detected by specialized epithelial cells, sensory nerve endings is found in the skin, eyes, ears, nose and tongue.
- Secretions specific chemical substances (enzymes, hormones, and lubricated fluids).
- Absorption of nutrients from the digestion of food
- Excretion in the kidneys excretes waste products from the body and reabsorbs needed materials from the urine. Sweat is also excreted from the sweat glands
- Filtration found in kidneys
- Diffusion promotes gasses, liquids, and nutrients it can do this because how thin it is (found in lungs)
Epithelial General Characteristics
- Arrangement of cells – composed of closely packet cells and their continuous sheets which are held together by tight junctions and desmosomes (macula adherins) which are specialized for cell to cell adhesions.
- Polarity – surfaces
- Connective tissue support – is support that is given to epithelium physically and it provides nutrients
- Vascularity – blood supply. Epithelium tissue is A vascular (doesn’t have blood supply but has nerve intervasion)
- Regeneration – high rate regeneration (rapid repair) it will regenerate as long as it receives proper nutrients
Apical Surfaces
Upper or free surface of epithelial tissue; can be smooth and slick but most will have microvilli or cilia
Microvilli
Fnger like extensions or the plasma membrane they increase the surface area in epithelial that absorb and secrets substances. It is often so dense that the cell apexes have a fuzzy appearance (brush boarder)
Cilia
Found in specific spaces (lining of trachea), they are tiny hair like projects that propel substances along their free surfaces.
Basal Surface
Lower attached surface of epithelial tissue
Basal Lamina
None cellular, it’s a thin cellular sheet of glycol-proteins + fine collagen fibers. It acts as a selective filter that determines which molecules can cross from the connective
Reticular Lamina
A layer of extra cellular material which contains collagen protein
Basement Membrane
Formed by the two lamina (basal and reticular lamina)
Classification - Number of Cell Layers
A. Simple epithelia – single cell layer and is typically found where absorption, secretion, and filtration occur.
B. Stratified epithelia – composed of 2 or more cells layers stacked one on top of the other and is common in high abrasion areas where protection is important (skin surface and inside the mouth)
Classification - Cell Shape
A. Squamous cells – flattened and scale like
B. Cuboidal cells – box like they are as tall as they are wide
C. Columnar cells – tall and column shaped
Simple Squamous Epithelia
- Description – single layer of flatten cells with disc shaped central nuclei, this is the simplest of the epithelia
- Functions – allows passage of materials by diffusion and filtration and also secreted lubrication
- Locations – where protection is NOT important, kidney glomeruli, air sacs of the lungs, lining of the heart, lining of blood vessels, lining of lymphatic vessels, and lining of ventral body cavity
Endothelium
Specialized, simple squamous epithelium found in the lymphatic vessels and in all hollow organs of the cardiovascular systems (blood vessels and the heart) capillaries consists exclusively of endothelium and its thinness encourages the efficient exchange of nutrients and wastes between the bloodstream and surrounding tissue cells.
Mesothelium
The epithelium found in serous membranes lining the ventral body cavity and covering its organs
Simple Cuboidal Epithelium
- Description – single layer of cube like cells with large sphere central nuclei
- Functions – secretion and absorption
- Locations – in the kidney tubules, ducts and secretory portions of small glands and surface of the ovaries
Simple Columnar Epithelium
- Description – single layer of tall cells with round to oval nuclei some contain cilia and some layers may contain mucus secreting unicellular (goblet cells)
- Functions – absorption and secretion of mucus, enzymes and other substances, cilia types are going to propel mucus
a. Goblet cells – mucosa pockets - Locations –lines most of digestive tract, gallbladder, and excretory ducts of some glands. Ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus
Pseudostratified Columnar Epithelium
- Description – single layer of cells of differing heights, some not reaching, the free surface; nuclei seen at different levels; may contain goblet cells and bear cilia
- Functions – secretion, particularly of mucus; propulsion of mucus by ciliary action
- Locations – nonciliated type in male’s sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract
Stratified Squamous Epithelium
- Description – thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers
- Functions – protects underlying tissues in areas subjected to abrasion
- Locations – nonkeratinized type forms the moist lining of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane