Ch 4 Flashcards
Tissue
~Tissues are a group of cells with a common embryonic origin that function together to carry out specialized activities. ~They include various types, ranging from hard (bone) to semisolid (fat) to liquid (blood).
Histology
is the study of the microscopic anatomy of cells and tissues – it is a branch of pathology
Intracellular Junctions
~Tissues are formed by grouping cells together using a variety of Intercellular Junctions . ~Intracellular Junctions connect adjacent cells mechanically at the cell membranes or through cytoskeletal elements within and between cells.

Tight Junctions
are found where a leakproof seal is needed between cells. ~They keep materials from leaking out of organs like the stomach and bladder.

Adherens Junctions
make an adhesion belt (like the belt on your pants) that keeps tissues from separating as they stretch and contract.

Adherens Junctions Cadherin
is a glycoprotein that forms the belt-like “plaque”.

Desmosomes
act as “spot welds”. They also use cadherin glycoprotein (plus intermediate filaments) to hook into the cytoplasm.

Hemidesmosomes
are half-welds that join cells to the basement membrane.

Gap Junctions
are pores (connexons) that allow small substances like ions to pass between cells. If one of the cells gets sick or dies, these seal like a hatch to prevent damage to other cells.

4 Basic Tissues
~Of all the cells in the body, they combine to make only 4 basic tissue types:
~Epithelial tissues
~Connective tissues
~Muscular tissues
~Nervous tissues
Epithelial tissues
cover body surfaces and form glands and line hollow organs, body cavities, and ducts.

Connective tissues (C.T.)
protect, support, and bind organs. ~Fat is a type of C.T. that stores energy. ~Red blood cells, white blood cells, and platelets are all C.T.
Muscular tissues
generate the physical force needed to make body structures move. They also generate heat used by the body.
Nervous tissues
detect changes in the body and respond by generating nerve impulses.
4 Basic Tissues
Tissues of the body develop from three primary germ layers: Endoderm, Mesoderm, and Ectoderm
~Epithelial tissues from all three germ layers
~C.T. and muscle are derived from mesoderm.
~Nervous tissue develops from ectoderm.
Epithelium
~Epithelium is used to line surfaces and form protective barriers. Epithelium is also good at secreting things like mucous, hormones, and other substances .
~All epithelia have a free apical surface and an attached basal surface.

Epithelium
~The basal layer of the epithelium secretes a basal lamina; the underlying C.T. secretes a reticular lamina.
~Together the basal lamina and the reticular lamina form a non-cellular basement membrane on which the epithelium sits.

Epithelium
Epithelia are named according to the shape of their cells, and the thickness or arrangement of their layers (of cells).
~simple
~pseudostratified
~stratified

Epithelium
Naming epithelia according to shape
~squamous: Flat, wide “paving stone cells”
~Cuboidal: cells as tall as they are wide
~Columnar: cells taller than they are wide

Simple Squamous Epithelium
is composed of a single layer of flat cells found: ~In the air sacs of lungs ~In the lining of blood vessels, the heart, and lymphatic vessels ~In all capillaries, including those of the kidney. ~As the major part of a serous membrane

Simple Cuboidal Epithelium
~is composed of a single layer of cube shaped cells. ~It is often found lining the tubules of the kidneys and many other glands.

Simple Columnar Epithelium
forms a single layer of column-like cells, ± cilia, ± microvilli, ± mucous (goblet cells). ~Goblet cells are simple columnar cells that have differentiated to acquire the ability to secrete mucous.

Pseudostratified Columnar Epithelium
~ appears to have layers, due to nuclei which are at various depths. In reality, all cells are attached to the basement membrane in a single layer, but some do not extend to the apical surface. ~Ciliated tissue has goblet cells that secrete mucous.

Stratified Squamous Epithelium
~has an apical surface that is made up of squamous (flat) cells. ~The other layers have different shapes, but the name is based on the apical layer. ~The many layers are ideal for protection against strong friction forces.






