structural organization in animals Flashcards
the organisation of a group of similar cells along intracellular substances performing a similar function in multicellular animals
tissues
general features of epithelial
free surface faces either body fluid or outside environment; provides a covering or lining for some part of the body. compactly packed with little intercellular matrix
On what basis are the cells of simple epithelium further divided into three types
On the basis of structural modification of the cells, simple epithelium
is further divided into three types
Three types of simple epithelium
Squamous, Cuboidal, Columnar
Features Squamous epithelium
- single thin layer of flattened cells with irregular boundaries
Location of squamous epithelium
- Found in: walls of blood vessels, air sacs of lungs
Function: Squamous epithelium
involved in functions like forming a diffusion boundary
Features: Cuboidal epithelium
composed of a single layer of
cube-like cells
Location: Cuboidal epithelium
commonly found in
1. ducts of glands
2. tubular parts of nephrons in kidneys
3. epithelium of proximal convoluted tubule (PCT) of nephron in the kidney has microvilli (brush bordered)
Functions: Cuboidal
Secretion and Absorption
Features: Columnar Epithelium
composed of a single layer of tall and slender cells. Their nuclei are located
at the base. Free surface may have microvilli.
Location: columnar
lining of stomach and intestine
function: columnar
secretion and absorption
If the ____________ bear cilia on their free surface they are called ciliated epithelium
columnar or cuboidal cells
function: ciliated
Their function is to move particles or
mucus in a specific direction over the epithelium.
location: ciliated
inner surface of hollow organs like bronchioles and fallopian tubes.
types: glandular
They are mainly of two types:
1. unicellular: isolated glandular cells (goblet cells of the alimentary canal)
2. multicellular: consisting of cluster of cells
(salivary gland)
glandular on the basis of mode of pouring of secretion
exocrine and endocrine
Exocrine glands secrete
mucus, saliva, earwax, oil,
milk, digestive enzymes and other cell
products. These products are released
through ducts or tubes.
endocrine glands
do not have ducts. Their products called hormones are secreted directly into the fluid bathing the gland.
function: compund epitheliummmmmm
Compound epithelium is made of more
than one layer (multi-layered) of cells and thus has a limited role in secretion and absorption. Their main function is to provide protection against chemical and mechanical stresses.
location: compound epitheliyum :P
- They cover the dry surface of the skin
- the moist surface of buccal cavity
- pharynx
- inner lining of ducts of salivary glands and of pancreatic duct
Types of cell junctions in epithelium and other tissues
- Tight junctions help to stop substances
from leaking across a tissue. - Adhering junctions perform cementing to
keep neighbouring cells together. - Gap junctions facilitate the cells to
communicate with each other by connecting the cytoplasm of adjoining
cells, for rapid transfer of ions, small molecules and sometimes big molecules.
