Structural Organisation in Animals 1 Flashcards
study of tissue and father of study of tissue
histology
bichat is father of tissue
he coined the word animal tissue
grew coined the word plant tissue
basic features of epithelial tissues
epithelial tissue- tissue which grows on other tissue( mainly connectiv tissue)
these originate first during embryonic devvelopment
Epithelial cells are compactly packed
with little inter cellular matrix.
Due to less intercellular spaces blood vessels, lymph vessels and capillaries are unable to
pierce this tissue so blood circulation is absent in epithelium. Hence cells depend for their
nutrients on underlying connective tissue.
high power of regeneration
what is the basement membrane? what are the two types of basemeent membrane/
(i) epithelial cells depend upon abasement membrane for nutrition
(ii) basement membrane is secreted by epithelial tissue and connective tisue
(iii) it is a non living, selectively permeable layer.
(iv) 2 parts:
* basal lamina: secreted by epithelium/ made of glycoproteins
*fibrous lamina: secreted by connective/ made of mucopolysaccharide or hyaluronic acid with fibres
what are the cell junctions
(A) Tight Junctions help to stop substances from leaking across a tissue.
(B) Adhering junctions perform cementing to keep neighbouring cells together. also called as desmosomes/ macula adherens. These are mainly found in no stretchable epithelium. They provide mechanical uppoer
(C) 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.
(D) Interdigitation finger like processes of plasma membrane which enter into cytoplasm of
adjacent cell. mainly found in stretchable or transitional eptihelium
modifications of plasma membrane: 1
(microvilli)
name: brush bordered
minute projections/ non contractile/non motile
these help increase surface area for secretion absorption
found in:
-proximal convoluted tubule of npehron
-walls of intestines
-gall bladder
modifications of plamsa membrane: 2
cilia/kinocilia
-long cylindrical projections uniform dimater from base to apex
- motile/contractile
name: ciliated
- functions:
help in the mvmnt or locomotion of particle/mucuous in an uniform direction
location:
- bronchi/bronchioles/tracjea
-fallopian tubes
-ependymal epithelium ( mvmnt of cerebrospinal fluid in brain and spinalcord)
modification of plasma membrane: 3
stereocilia
-conical shape
name: stereociliated
- nonmotile/non contractile
- functions:
increase surface area
location:
- epididymis/ vas deferens/ middle ear
simple sqamous epithelium
-it is called pavement epithemlium due to tile like appearance
-it is called tesselated epithelium due to wavy appearance in blood vessel and coelom.
-has round, flat nucleus present at the centre
-function: filtration/diffusion
location:
- Outer surface of intestine.
- **Bowman’s capsule (Podocyte)
- Alveoli of lungs (Pneumocytes type-I) (air sacs of lungs)
- Mesothelium – Lining of coelom is called as mesothelium.
**- Endothelium – Inner lining of blood vessels and lymph vessels.
- Endocardium – Inner most lining of heart is also made up of simple squamous epithelium.
-** Thin part of loop of Henle of nephron.**
- Peritoneum
simple cuboidal epithelium
-cells cube in shape
-nucleus is spherical and at centre
-functions: absorption, secretion, excretion
- Follicle of Thyroid gland
- Type II Pneumocytes of alveoli
- Acini of Pancreas
- Secretory unit of sweat glands
- Iris, Choroid, Ciliary body of eye, Epithelium of retina
- Distal Cconvoluted Tubule of nephron
- Thick part of loop of Henle
- This epithelium is also called Germinal epithelium because in gonads (testes & ovaries)
cubodial cells divide to form sperm & egg.
modifications of simple cuboidal epithelium
(i) brushbordered cuboidal epithelium
found in PCT of nephron
(ii) ciliated cuboidal nephron
found in collecting duct
columnar epithelium
liver bile duct and uterus
glandular columnar epithelium: stomach+large intestine
glandular brush bordered: small intestine
brush bordered: gall bladder
ciliated columnar epithelium: fallopian tubes, ependymal epithelium of brain to push csf
stereociliated columnar epithelium: epididymis, vas deferens
what is pseudostratified epithelium
*These cells are pillar like in shape so it is also a modification of columnar epithelium.
* In this epithelium 2 types of cells are present i.e. Tall cell and short cell.
* Nucleus in both cells are present on different level so it appears bilayered.
* All cells are present on single basement membrane so it is unilayered.
other name of pseudostratified
Pseudostratified Ciliated Columnar Glandular Epithelium {PSCCGE}
pesudostratified epithelium
-respiratory epithelium of nasal chambers, bronchi and trachea
explain layers of stretchable or transitional epithelium
▪ Multilayered : 4-6 layers of cells are present
▪ Innermost layer - cube like cell
▪ Middle 2-4 layers - pear shape or
umbrella shaped cells/ polyhedral
cells
▪ Outermost 1-2 layers - oval shaped cells
present in:
Renal pelvis
▪ Ureter
▪ Urinary bladder
▪ Proximal part of male urethra
Note:
Mainly present in urinary system.
So also called Urothelium.
