Human Anatomy - Epithelial tissue Flashcards
What is a tissue?
A group of closely associated cells that perform related functions and are similar in structure.
What are the four tissue types?
What are their general functions?
Epithelial - covering
Connective - support
Nervous - control
Muscle - movement
Epithelial Tissue
______ a body surface or ____ a body cavity.
Forms parts of most ______.
Covers
Lines
Glands
What are the different functions of epithelial tissue?
protection
absorption, filtration and ion transport
excretion, secretion
Forms slippery surface
What are the special characteristics of epithelium?
- Cellularity
- Specialized contacts
- Polarity
- Supported by connective tissue
- Avascular but innervated
- Regeneration
Describe cellularity as it pertains to epithelial tissue.
Epithelial tissue is almost entirely composed of cells.
Describe specialized contacts as it pertains to epithelial tissue.
Cells of epithelial tissue are joined by special junctions.
These gap junctions allow for communication and for the cells to work as functional unit.
Describe polarity as it pertains to epithelial tissue.
Cell regions of the apical surface differ from the basal surface
How does epithelium receive nutrients without a dedicated blood supply?
Epithelia receive nutrients from underlying connective tissue.
Capillaries go through connective tissue but not through epithelium
Describe regeneration as it pertains to epithelial tissue.
Lost cells are quickly replaced by cell division.
How is epithelium classified?
First name of the tissue indicates the number of cells:
Simple - 1
Stratified 2 or more
Last name of the tissue describes the shape of the cells:
Squamous - flat
Cuboidal - cube-shaped
Columnar - column-shaped
How does structure relate to function? Protection = \_\_\_\_\_\_\_\_ Transport = \_\_\_\_\_\_\_\_ Filter = \_\_\_\_\_\_\_\_\_ Stomach = \_\_\_\_\_\_\_\_
Stratified
Simple
Simple
Simple
Endothelium and mesothelium are both what type of epithelium?
Simple squamous
What is endothelium?
Slick lining of hollow organs in the circulatory system and in the inner layer of the heart.
Inner covering
What is mesothelium?
Lines peritoneal, pleural and pericardial cavities.
Covers the visceral organs of those cavities.
Middle covering.
What is the function of simple squamous epithelium?
Passage of materials by passive diffusion, osmosis and filtration.
Secretion in serous membranes.
Where is simple squamous epithelium located?
Renal corpuscles
Alveoli of lungs
Lining of heart, blood and lymphatic vessels (endothelium)
Lining of ventral body cavity and serosae (mesothelium)
What is the function of simple cuboidal epithelium?
Secretion and absorption
What is the location of simple cuboidal epithelium?
Kidney tubules
Secretory portions of small glands
Ovary surface
What lines the duct of a lumen?
Simple cuboidal epithelium
Describe simple columnar epithelium.
Single layer of column shaped epithelial cells.
Some bear cilia on their apical surface.
May contain goblet cells.
What is the function of simple columnar epithelium?
Absorption
Secretion of mucus, enzymes and other substances
Ciliated type propels mucus or reproductive cells
Where is simple columnar epithelium located?
Non-ciliated forms
- line GI tract, gallbladder, ducts of some glands
Ciliated form:
- lines small bronchi, uterine tubes, uterus
What is the purpose of cilia?
Move material across the surface of cells.
What do goblet cells do?
Secrete mucin
What is the lamina propria?
Connective tissue underlying mucus secreting membranes.
Pseudostratified epithelium:
All cells originate at the ________ _______
Only ______ cells reach the apical surface
May contain ______ ____ and bear _____
______ lie at varying heights within cells, giving the false impression of _________
Basement membrane tall goblet cells cilia Nuclei stratification
Describe pseudostratified epithelium.
All cells originate at the basement membrane but, nuclei at varying heights give the impression of stratification.
May contain goblet cells and some bear cilia.
Only tall cells reach the apical surface.
What is the function of pseudostratified columnar epithelium?
Secretion of mucus
Propulsion of mucus by cilia
Where is pseudostratified epithelium located?
Non-ciliated: - ducts of male reproductive tubes - ducts of large glands ciliated: - lines trachea and most of URT
Describe the mucociliary escalator.
Mucus lubricates the respiratory system and catches bacteria and debris.
Cilia of the URT beats unidirectionally back up the URT to either expel the mucus or swallow it and digest it with stomach acid
What are the properties of stratified epithelia?
Contains two or more cells
Regenerate from below
Major role is protection
Named according to the shape of cells at the apical layer
Describe stratified squamous epithelium.
Multiple layers of flat cells. (squamous on apical layer)
Thickest epithelial tissue.
Adapted for protection against abrasion.
Can be keratinized or non-keratinized
Describe keratinized stratified squamous epithelium.
Dry Located in the epidermis Contains the protective protein keratin Waterproof Surface cells are dead and full of keratin
Describe non-keratinized stratified squamous epithelium.
Apical layer and layers deep to it remain moist.
Forms moist lining of body openings.
Wet
What is the function of stratified squamous epithelium?
Protects underlying tissues from abrasion.
Where is stratified squamous epithelium located?
Keratinized - epidermis
non-keratinized - mouth, esophagus, anus, vagina, urethra
What is the function of stratified cuboidal epithelium?
Protection
Where is stratified cuboidal epithelium located?
Forms the ducts of:
- mammary glands, salivary glands, largest sweat glands
Stratified cuboidal epithelium is generally ___ layers.
2
Describe stratified columnar epithelium.
Multiple layers;
Basal cells are generally cuboidal, apical cells are elongated
What is the function of stratified columnar epithelium?
Protection and secretion
Where is stratified columnar epithelium located?
Rare
Found in male urethra and large ducts of some glands
Describe transitional epithelium.
Basal cells are usually cuboidal/columnar and apical cells are squamous.
Not as many layers as stratified squamous.
What is the function of transitional epithelium?
Stretches and permits distension of urinary bladder
Where is transitional epithelium located?
lines inside of hollow urinary organs.
What are exocrine glands?
Glands who secrete their products onto the body surface or into a body cavity.
Local activity
Which glands are exocrine?
Mucus-secreting glands
Salivary glands
Sweat and oil glands
Liver and pancreas
Describe the goblet cell.
Produce the glycoprotein mucin.
Unicellular exocrine gland.
What is the purpose of mucin?
When combined with water, becomes mucus which, protects and lubricates internal body surfaces.
Where is the mucin located in a goblet cell?
Secretory vesicles in goblet cells contain mucin.
What are the different epithelial surface features?
Apical: Cilia and Microvilli Basal: Basal lamina Basement membrane
What are microvilli?
Finger-like extensions of plasma membrane which function to increase surface area.
Important for secretion and absorption.
Where are microvilli located?
Small intestine and kidney
What are cilia?
Whip-like, highly motile extensions of apical surface membranes.
Move in one direction to push material over the surface of epithelial tissue
What is the basal lamina?
Acellular supporting sheet between the epithelial tissue and underlying connective tissue.
Consists of proteins secreted by epithelial cells
What are the functions of the basal lamina?
Selective filter - prevents inside-out/outside-in movement of material
Scaffolding: for tissue regeneration
What is the basement membrane?
Basal lamina + reticular lamina
Often interchangeable with basal lamina.
What is the basis of a scar?
Caused by the destruction of the scaffolding of the basement membrane leading to improper tissue regeneration.
What is the purpose of stitching?
Minimize appearance of a scar by getting tissue close enough for communication.
Kartagener’s syndrome is an _______ issue.
Diabetes is a ______ issue.
Apical
Basal
What is Kartagener’s Syndrome?
Immotile cilia in which dynein arms fail to form.
What are symptoms of Kartagener’s?
Chronic respiratory infections, infertility, hearing loss, frequent headaches due to stagnant CSF.
If left untreated, diabetes can cause _______ of the basement membrane. Why?
Thickening
Increased glucose causes thickening of basement membrane.
Symptoms include loss of eyesight and kidney problems.
