Class 7 - Cellular Junctions, Tissue Repair Flashcards
Cellular junctions + 4 types
Connections between two cells.
- Tight junctions
- Desmosomes
- Hemidesmosomes
- Gap junctions
Tight junction
Interlocking linkage between two cells.
Seals off intercellular space, preventing passage
e.g. in stomach prevent digestive juices from seeping through
Desmosome
Holds two cells together. Resists mechanical stress. Hook-like. Common in epidermis/other epithelia
Hemidesmosome
Anchors basal cells of an epithelium to basement membrane.
Gap junctions + locations (5)
Channel between cells formed by ringlike connexon.
Allows ions, nutrients, and other small solutes to pass through
- Cardiac muscle
- Smooth muscle
- Embryonic tissue
- Lens
- Cornea
Gland + 3 types
Cell or organ that secretes substances for use elsewhere in the body or released them for elimination
Usually composed of epithelial tissue in a connective tissue framework and capsule
- Exocrine glands
- Endocrine glands
- Unicellular glands
Exocrine glands + structure (4)
Maintain contact with surface of epithelium by way of duct. Surfaces can be internal (sweat, tear glands) or external (pancreas, salivary glands).
- Capsule - connective tissue covering
- Septa or trabeculae - extensions of capsule that divide interior of gland into lobes.
- Stroma - connective tissue framework
- Parenchyma - perform task of synthesis and secretion
Endocrine glands + 3 locations
Have no ducts and instead have blood capillaries. Secrete hormones directly into blood.
Examples: thyroid, adrenal and pituitary glands
Unicellular glands
Secretory cells found in an epithelium that is predominantly non-secretory.
Can be exocrine or endocrine.
Example: goblet cells in trachea; endocrine cells of stomach.
Exocrine gland structure: 2 duct shapes and 3 secretory portions
- Simple - unbranched
- Compound - branched
a. Tubular - Narrow portion, uniform diameter to secretory portion
b. Acinar - Secretory cells for dilated sac
c. Tubuloacinar - Combination of tubular and acinar
3 types of gland secretions
- Serous glands - Thin, watery secretions (sweat, milk, tears).
- Mucous glands - Produce mucin
- Mixed glands - Both serous and mucous cell types
3 modes of exocrine gland secretion
- Eccrine glands - Release products by exocytosis
- Apocrine secretion - Lipid droplet covered by membrane buds from cell surface.
- Holocrine secretion - Cells accumulate product and entire cell disintegrates
3 types of membranes
- Cutaneous membrane - the skin; largest membrane. Stratified squamous epithelium (epidermis) on connective tissue (dermis).
- Mucous membrane - Lines passages that open to external environment. Absorptive, secretory, and protective functions; often have goblet cells.
- Serous membrane - Lines some internal body cavities (pleurae, pericardium, peritonium).
Simple squamous epithelium (mesothelium) on areolar tissue. Produces serous tissue
Sublayers of a mucous membrane
- Epithelium
- Lamina propria (areolar tissue)
- Smooth muscle
3 methods of tissue growth
- Hyperplasia - Growth through cell multiplication (e.g. embryonic grown).
- Hypertrophy - Enlargement of preexisting cells
- Neoplasia - Development of a tumor composed of abnormal, nonfunctional tissue
2 types of tissue development
- Differentiation - Development of more specialized form and function by unspecialized tissue
- Metaplasia - Changing from one type of mature tissue to another
Stem cells and developmental plasticity
Undifferentiated cells not yet performing any specialized function. Have potential to differentiate into one or more mature functional cells.
Developmental plasticity - Ability of a stem cell to give rise to a diversity of mature cell types
Embryonic stem cells + two types
Compose early human embryo.
- Totipotent stem cells - From cells of very early embryo; unlimited developmental plasticity
- Pluripotent stem cells - From cells of inner cell mass of embryo. Can develop into any cell type of the embryo but not accessory organs of pregnancy
Adult stem cells + 2 types
Undifferentiated cells found in mature organs.
- Multipotent - Able to develop into two or more cell lines
- Unipotent - Produce only one cell type
Two methods of tissue repair
- Regeneration - Replacement of cells by the same cell type as before. Restores normal function.
- Fibrosis - Replacement of damaged cells with scar tissue, does not restore function
Stage of healing for skin wound
- Mast cells release histamine—>dilated blood vessels—>makes capillaries more permeable
- Plasma carries antibodies and clotting proteins to wound
- Blood clot forms
- Scab forms
- Macrophages phagocytize tissue debris
- New capillaries sprout from nearby vessels
- Deeper portions of cut infiltrated by capillaries and fibroblasts (transform into granulation tissue)
- Macrophages remove blood clot
- Fibroblasts deposit new collagen
- Nearby epithelial cells migrate beneath scab (epithelium regenerates)
- Underlying connective tissue undergoes fibrosis
3 types of tissue degeneration/death
- Atrophy - Shrinkage of tissue through loss in cell size or number due to aging (senile atrophy) or lack of use (disuse atrophy).
- Necrosis - Pathological tissue death.
- Apoptosis - Normal death of cells that have completed their function. Phagocytized by macrophages.
2 types of necrosis
- Infarction - Sudden death of tissue when blood supply is cut off completely
- Gangrene - Necrosis due to insufficient blood supply, happens over time
3 types of gangrene
- Dry gangrene - Occurs due to continual pressure in skin
- Wet gangrene - Liquefaction of internal organs with infection
- Gas gangrene - From infection that results in hydrogen bubbles in tissues
