Tissue covers exposed surfaces, lines internal passageways & chambers, forms glands
Functions of Epithelial tissues may include:
1.Protection (cover surfaces & line cavities)
2.Absorption & Secretion (ex. kindney tubles, digestive tract)
Glands: the secretory part of a gland. (Ex. sweat gland)
General characteristics of epithelial tissues include :
1.Tightly packed cells
3.free surface:eposed to the outside of the body/to an internal organ.
4.Basement membrane: Made of collagen & glycoproteins/attaches the epithelium to connective tissue underneath
7.Keratinized/non-kertinized,cillia, goblet cells:mucus filled cell(unicellular)
Functions of the Basement Membrane:
A. attaches epithelium to connective tissues located under the basement membrane
C.Provides a surface for cells to expand along when they undergo mitosis
Where do epethilial cells get their nutrients if the tissue is avascular?
From the connective tissues under the basement membrane.
How do you classify epithelial tissues?
Epithelial tissue Shapes:
Layers of Epithelial Tissues:
A. Simple (one layer)
B.Stratified (Multiple layers of cells)
Simple squamous tissue
- One layer of flat cells
- lines blood vessels,body cavities air sacs; found in kidney tubles
- provides a thin layer of cells for diffusion across the cells
Specific types of simple squamous tissues:
Endothelium (lines the inner surface of the heart and all the blood vessels)
Mesothelium (lines the abdominal & thoracic cavity). The pleura, pericardium, and peritoneum contain a superficial layer of mesothelium.
Simple Cuboidal Tissue
- One layer of cuboidal cells
- Found in the ducts, glands, kidney tubles, thyroid glands
- often involved in secretion and absorption
Simple Columnar Tissue
- one layer of cells
- involved in secretion and absorption
- found in cilliated tissues found in the bronchi,uterine tubes. Smooth tissues found in digestive tract & gall bladder
- some may be goblet cells that produce mucus
- may have microvilli on the free surface
Why would goblet cells be necessary in the digestive tract?
to protect tissues from highly acidc enviroment.
Why would a columnar epithelium in the digestive tract need microvilli?
Increase surface area, increase absorption.
Stratified Sqaumous Tissue
- Several layers of cells. Cells at the free surface are flat
- found in the skin,lining of the mouth, esophagus,vagina & rectum
- found where protection is needed.
Why does mitosis occur near the basement membrane & not the free surface?
Cells at the basement membrane are alive and recieve nutrients. Cells at the free surface are dead.
What is Keratinized stratified squamous tissue?
- Tissue that is tough & water resistant
- produces the protein Keratin
- protects againt abraison, mechanical stress, and dehydration
Stratified cuboidal tissue & Stratified columnar tissue
- Stratified cuboidal tissue is found in swaet gland ducts, stratified columnar tissue is found in salivary gland ducts
- tissue function primarily as protection
- Combination of differently shaped cells that can change their shape (for stretch & recoil)
- lines the utuerus & bladderf
- when the cells change shape from cuboidal to squamous the organ expands
- appears to have more than one layer, but every cell touches the basement membrane
- Found lining the respiratory tract & part of the male reproductive tract
- often ciliated, tissue typically has goblet cells to produce mucin.
- exocrine gland (into a duct)
- endocrine gland (hormone secretes into bloodstream)
Unicellular gland that makes mucin?
mucus gland (goblet cells)
Examples of Exocrine glands: