WEEK 5: ORGANISATION OF CELLS INTO TISSUES Flashcards
What is epithelial tissue?
Tightly-bound contiguous (adjoining) cells forming sheets covering the body surface or lining the body cavities and their invaginated glands.
State the three embryonic layers epithelial tissues are derived from.
They are derived from the three embryonic layers (ectoderm, mesoderm and endoderm).
State the characteristics of epithelial tissue.
1.Cells are tightly bounded together.
2.Little intercellular spaces and extracellular matrix.
3.Separated from the underlying connective tissue by basal lamina.
4.Avascular and it is nourished by diffusion from underlying tissues.
5.Have a high rate of regeneration.
State the functions of epithelial tissue.(8)
1.Protection.
2.Trans-cellular transport.
3.Secretion.
4.Absorption.
5.Selective permeability.
6.Sensation.
7.Digestion.
8.Excretion
State the different names which can be assumed by epithelium based on its location.
1.Epidermis for external surface.
2.Mesothelium for body cavities.
3.Endothelium for blood vessels.
4.Neuroepithelium.
5.Glandular epithelium.
Describe how the epithelial tissues are named.
1.The first name indicates the number of cell layers present.
Simple- one layer
Stratified- more than one layer
2.The second describes the shape of its cells
Squamous, cuboidal, and columnar
Single layer of flat cells with central nuclei.
Function:
Exchange of gases and fluids.
Sites:
Lung alveoli, endothelium, mesothelium, parietal layer of Bowman’s capsule and thin segments of loop of Henle.
What epithelium is this?
Simple squamous
Single layer of tall cylindrical or hexagonal cells with oval basal nuclei.
Function:
Secretion, absorption, transport.
Sites:
Digestive tract & gall bladder (lined by microvilli), large ducts and female genital ducts & small bronchi (lined by cilia).
Simple columnar.
Single layer of cells, all rest on basal lamina but not all reach to surface, with nuclei arranged in many rows.
Function:
Protection, secretion, absorption.
Sites:
Respiratory tract ( kinetic cilia - motile).
Epididymis & vas deferens (stereocilia -nonmotile)
What epithelium is this?
Pseudostratified Columnar
Basal cells are cuboidal, next layers are polygonal, the surface cells are flattened.
Function:
protection.
Sites:
Epidermis (keratinized).
Oral cavity, oropharynx, esophagus & vagina (non-keratinized).
What epithelium is this?
Stratified squamous
Two layers of cuboidal cells.
Function:
Transport and protection
Sites:
Duct of sweat glands. mammary glands, sweat glands, salivary glands, and pancreas.
Forms the lining of ovarian follicles and seminiferous tubules
What epithelium is this?
Stratified cuboidal
Basal cells are cuboidal, next layers are polygonal, the surface cells are columnar.
Function:
Protection and transport.
Sites:
Conjunctiva of the eye.
Large ducts.
Parts of male urethra
What epithelium is this?
Stratified Columnar
Resembles both stratified squamous and stratified cuboidal. Basal cells are cuboidal or low columnar, next layers are polygonal, the surface cells are columnar, dome-shaped binucleated (in empty bladder), but change to flattened cell in full bladder.
Function:
Protection, transport & adaptation for stretch.
Sites:
Urinary tract (calyces, renal pelvis, ureter, bladder and parts of urethra)
What epithelium is this?
Transitional epithelium
State the 3 cell surfaces.
1.apical,
2.lateral and
3.basal surfaces
State the 4 apical modifications.
1.Microvilli- They increase the surface area of the cell to increase its absorption.
2.Cilia- Cilia propel the mucus and other structure over the surface of the epithelium by rapid rhythmic oscillations.
3.Flagella- Present only in the spermatozoa
4.Cell coat (glycocalyx)
-Glycoprotein attached to the external surface of the cell membrane.
-Formed of carbohydrate chain attached to the transmembrane protein of the plasmalemma.
- Contains some hydrolytic enzymes and alkaline phosphatase.
-They function in protection and cell recognition.
State the 4 main lateral modifications.
1.Occluding (tight) junction- Its function to prevent membrane proteins and water-soluble molecules from passing between the cells.
2.Adhering junction- .Function is not only joins the two cell membranes to each other, but also links the cytoskeleton of both cells.
3.Desmosome- Are weld-like junctions that help to resist the shearing forces.
Gap junction- They are tiny pores communicating between two adjacent cells and permit the passage of ions, amino acids, AMP and certain hormones between the cells.
-They are under regulation, so they may be opened or closed.
State the 3 basal modifications.
1.Basement membrane.
2.Plasma membrane enfolding- Multiple basal enfolding of cell membrane to increase the surface area for transport.
3.Hemi-desmosome- Attach the basal cell membrane to the underlying basal lamina.
Describe glandular epithelium.
Glands originate from the epithelial surface, penetrate the underlying connective tissue and manufacture a basal lamina around themselves.
Outline the different ways of classifying glands.
1.MODE OF SECRETION
-Holocrine gland: The whole cell is destroyed and detached, e.g. sebaceous gland. (A)
-Merocrine gland: The cell is intact and it secretes through exocytosis of secretory vesicles, e.g. salivary glands. (B)
-Apocrine gland: the apical part of the cell is detached, e.g. mammary gland. (C)
2.TYPE OF SECRETION
-Mucous: sublingual (salivary), Brunner’s glands (in duodenum) and goblets cells.
Serous: parotid salivary gland.
Seromucous: Submandibular.
Waxy: ceruminous gland (external ear).
Fatty: sebaceous glands.
Watery: sweat glands.
Milk: mammary glands.
Cellular: testis
3.WAY OF SECRETION
number of secretory cells,
4.DUCT SYSTEM
- Exocrine gland: means it pours its secretion through duct system to a particular place, e.g. salivary glands.
-Endocrine gland: has no ducts and it delivers its secretion directly to the blood stream, e.g. thyroid gland.
-Mixocrine gland: has both types, e.g. pancreas.
5.SHAPE OF SECRETORY UNITS
6.NUMBER OF CELLS
-Unicellular gland:
One cell only, e.g. goblet cells in the epithelium of mucosa of respiratory tracts and intestine.
Multicellular gland: Many cells and they pour their secretion into the duct system, e.g. salivary glands.
what is connective tissue?
These tissues connect and support other tissues of the body.
State the functions of connective tissue.
1.Mechanical support
2.Medium for exchange of nutrients & waste products
3.Energy store and thermal insulation
4.Defensive functions
a) Barrier b) Engulf bacteria
c) Antibodies
Outline the connective tissue cells.
1.Resident cell population
2.Wondering cell population
1.Resident cell population
Fibroblasts
Macrophages
Adipose cells
Mast cells
Undifferentiated mesenchymal cells
2.Wondering cell population
Lymphocytes
Plasma cells
Neutrophils
Eosinophils
Basophils
Monocytes
Outline the connective tissue fibers.
1.Collagen fibers –collagen
-. Collagen fiber formation involves events that occur both within and outside the fibroblast.
2.Reticular fibers –collagen
-Reticular fibers provide a supporting framework for the cellular constituents of various tissues and organs,
3.Elastic fiber ——-elastin
*Found in lungs, large arteries, ligamenta flava (connecting laminae of successive vertebrae)
State the 3 specialized connective tissue.
Specialized Connective Tissue:
1.CARTILAGE
*Prevents bones from rubbing against each other
*Does not contain nerves or blood vessels.
*Receives nutrition from perichondrium
*Cells are chondrocytes, matrix is a gel of chondroitin sulfate, hyaluronic acid, and chondronectin plus fluid.
-Fluid gives nutrients to the chondrocytes, which live in pockets called lacunae
-Fluid allows cartilage to be resilient and withstand compression
*Hyaline
-Found as articular cartilage at end of long bones and joints and connects ribs to the sternum.
-Nose, trachea, larynx
*Elastic
-Similar to hyaline cartilage but contains elastic fibers
-Give it flexibility, ability to bend
Found in pinnae, ear canal, epiglottis
*Fibrocartilage
-Found between vertebrae, in pelvis, and in knee joint
-Thick bundles of collagen, but few chondrocytes
2.BONE
-Compact, Cancellous
3.BLOOD
