General Anatomy (Epithelial Tissue) Flashcards
What are the four types of tissues?
- Connective tissue
- Epithelial tissue
- muscle tissue
- Nervous tissue
What is the epithelial tissue?
- Epithelial tissue covers or lines every body surface and body cavity
- Epithelial is composed of one or more layers of closely packed cells between two compartments
What are the characteristics of epithelial tissue?
- Cellularity - composed almost entirely of cells
- polarity - has specific top and bottom
- attachment - basal surface bound to basement membrane
- avascularity - no blood vessels, receive nutrients across apical surface or by diffusion
- Innervation - lots of nerve endings
- high regeneration capacity - epithelial cells are frequently damaged or lost to abrasion, so they are replaced quickly
What are the functions of epithelial tissue?
- physical protection - protect exposed and internal surfaces from dehydration, abrasion, destruction
- Selective permeability - act as gatekeepers to let some substances in and keep others out
- sensation - sense changes in the environment
What is basement layer?
Is extracellular layer between epithelium and connective tissue
What is a hemidesmosomes?
In some epithelial tissue, basal cells anchored to basement membrane with junctions called hemidesmosomes.
What are intercellular junctions?
- Junctions between cells in epithelium
What are tight junctions?
- anchor cells to each other
- prevent substances from passing between cells
- materials must move through cells, or are blocked from moving past cells
- found in intestinal lining
- Adhering junctions often deep to tight junctions
- form all the way around a cell
- support apical surface
- allows passage between cells below apical surface
What is the cell-cell attachment?
- Desmosomes attach cells yo each other
- bind epithelium together
- bind muscle cells
- resist shear forces
What is cell-cell communicating attachment?
- Gap junctions tunnel between two plasma membrane
- found in muscles
- Enables sharing of ions and proteins
- enables fast communication between cells
What are the two different type of epithelial tissue?
Simple - one cell layer thick
Stratified - more than two cell layers thick
What are the three different types of epithelial tissue?
Squamous - flattened
Cuboidal - cube shaped or roundish
Columnar - long and thin like a column
What is a microvilli?
- they are cylindrical, membrane-bound, finger like cytoplasmic projections emanating from the apical surface of absorptive cells
- found in the intestinal absorptive cells and the kidney proximal tubule cells
What is stereocilia?
- long, non-motile processes
- longer branched microvilli
- do not contain microtubules
- function is absorbing
- found lining part of male reproductive tract
What is a cilia?
- Cylindrical, motile structures that produce rapid back and forth movement in one direction
- contains central and peripheral microtubules surrounded by cell membrane
- permits movement of fluid or particulate matter over epithelial surface
- ATP is a source of energy for ciliary motion
- found in respiratory tract and uterine tube
What is the simple squamous epithelium?
Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm, the simplest of the epithelia
What is the function of the simple squamous epithelium?
Allows passage of materials by diffusion and filtration in sites where protection is not important, secretes lubricating substances in serosae
What is the location of the simple squamous epithelium?
- kidney glomeruli
- air sacs of lungs
- lining of heart
- blood vessels
- lymphatic vessels
- lining of ventral body cavity
Where are the simple squamous and cuboidal epithelium cells found?
- Amnion
- kidney tubules
What is the simple cuboidal epithelium?
Single layer of cube like cells with large spherical central nuclei
What is the function of the simple cuboidal epithelium?
Secretion and absorbing
What is the location of the simple cuboidal epithelium?
- kidney tubules
- ducts and secretory portions of small glands
- ovary surfaces
What is the simple columnar epithelium?
Single layer of tall cells with round to oval nuclei, some cells bear cilia, layers may contain mucus-glands
What is the function of simple columnar epithelium?
Absorbtion, secretions of mucus, enzymes and other substances, ciliated type propels mucus by ciliary action
What is the location of the simple columnar epithelium?
- no ciliated type lines most of the digestive tract
- gallbladder
- excretory ducts of some glands
- ciliated variety lines small bronchi
- uterine tubes
Where is the non-ciliated simple columnar epithelium and ciliated simple columnar epithelium?
- mucosa of small intestine
- uterine tube
What is the stratified squamous epithelium?
Thick membrane composed of several cell layers, basal cells are cuboidal or columnar and metabolically active, surface cells are flattened (squamous), in the keratinized type, the surface cells are full of keratin and dead, basal cells are active in mitosis and produce the cells of the more superficial layers.
What is the function of the stratified squamous epithelium?
Protects underlying tissues in areas subjected to abrasion
What is the location of stratified squamous epithelium?
Nonkeratinized type forms the moist linings of the esophagus, mouth and vagina, keratinized variety forms the epidermis of the skin, a dry membrane
Where is the nonkeratinized stratified squamous epithelium and keratinized stratified squamous epithelium cells?
- vagina
- epidermis of skin
What is pseudostratified columnar epithelium?
Single layer of cells of different heights, some not reaching the free surface, nuclei seen at different levels, may contain goblet cells and bear cilia.
What is the function of pseudostratified columnar epithelium?
Secretion, particularly of mucus, propulsion of mucus by ciliary action
What is the location of pseudostratified columnar epithelium?
- Nonciliated type in male’s sperm-carrying ducts and ducts of large glands
- ciliated variety lines the trachea
- most of the upper respiratory tract
What is transitional epithelium?
It is made of cells that can stretch. Cells look cuboidal when relaxed, look squamous when stretched. They are found in the lining of urinary bladder
What is the transitional epithelium?
Resembles both stratified squamous and stratified cuboidal, basal cells cuboidal or columnar, surface cells dome shaped or squamouslike, depending on like the degree of the organ stretch
What is the function of the transitional epithelium?
Stretches readily and permits distension of urinary organ by contained urine
What is the location of the transitional epithelium?
Lines the ureters, bladder and part of the urethra
What is glandular epithelium?
Composed of epithelial cells specialized and secrete
What are the products for endocrine and exocrine
Exocrine - ducts
Endocrine - blood
What are the components of serous acinus gland?
- consistency - thin, watery
- content - proteinaceous
- cytoplasm - zymogen granules
- nucleus - central rounded
- lumen - small lumen
- cell boundaries - indistinct
- H and E staining - darkly stained
- function - enzymatic action
- examples - parotid gland
What are the components of the mucous gland?
- consistency - thick and viscous
- content - mucopolysaccharides
- cytoplasm - mucinogen droplets
- nucleus - flat and peripheral
- lumen - large lumen
- cell boundaries - distinct
- H and E staining - lightly stained
- functions - protection and lubrication
- examples - sublingual gland
What is the merocrine gland (Eccrine)?
- secretion discharged through intact cell membrane
- by exocytosis
- no loss of cytoplasm
- example - protein content of mammary gland, parotid, pancreas, typical sweat gland
What is an apocrine gland?
- apical portion of cell disintegrate to discharge it’s secretion
- nucleus and basal portion remain intact from which cell can regenerate
- partial loss of the cytoplasm
What is the holocrine gland?
- entire cell disintegrate to discharge it’s secretion
- result in the death of the cell
- complete loss of the cytoplasm
What is the cytocrine gland?
- cell are released as secretion
