What are the four types of primary tissues?
Muscle, Epithelium, Connective tissue, Nervous tissue
What are the functions of epithelium? (6)
1) Protection2) Absorption3) Secretion4) Excretion5) Gas exchange6) Gliding btw inner body surfaces
What are 4 characteristics of epithelial tissue?
1) MORE cells and less extracellular matrix (Very crowded/dense)2) High rate of proliferation (often exposed to stress so must divide rapidly)3) Avascular (NO blood vessels)4) Polar (parts of the same cell are exposed to different environments)
What are the three domains of epithelial cells?
Apical, lateral, and basal
Where is the apical domain of epithelia tissue found? What structures are found in this domain?
Facing the external environment or lumen of tubular structureStructures: microvilli, cilia, and stereocilia
What is the function of microvilli?
increase surface area for absorption
What is actin's role in microvilli? What does it show up as in EM?
Anchors them to the cytoskeleton of the cell; shows up as grey material extending into the cell's terminal web
What is the terminal web of epithelial cells?
A network of actin filaments added by cytoskeleton proteins (spectrin, myosin, tropmyosin. Acts to anchor Microvilli to the cell.
What is spectrins role in microvilli?
Connects the terminal web to the apical cell membrane
What is myosin and tropomyosin's role in microvilli?
Contractile proteins that affect the size of the apical cell surface
What is the brush border?
Numerous, closely-packed Microvilli from epithelial cells that creates a border on the apical surface of the cell
Are microvilli motile?
No
What are stereocilia? Where are they found?
Very long branching finger-like projections found in the male reproductive system
What is the function of cilia? Where are cilia found in surplus?
To move fluid/cells over a tissue surfaceFound in respiratory tract (to move mucus)
Where do cilia originate from?
Basal bodies
What makes up cilia?
Axoneme and Basal body
What make a basal body?
Formed by 9 short triplets of microtubules with NO central microtubular component *Two out of the three microtubules of each triplet are continuous with axoneme
What makes an axoneme?
Two central microtubules surrounded by nine microtubules doublets.
What is Kartagener's syndrome and what causes it?
Caused by an issue with cilia and causes males to be sterile along with giving them the inability to move mucus through the respiratory tract
What are primary cilia? What are they made of?
Mechanoreceptors. Immotile cilia that are important in sensing the extracellular environment (antenna).Made up of 9 doublets with no central microtubules
What are terminal bars?
Unresolved, junctional complexes located at the lateral surface, but very close to the apical surface of cellsFormed by zonula occludens at apical surfaceFormed by zonula adherens directly belowFormed by macula adherens (desmosome)
What is the basement membrane of epithelial cells composed of?
Basal lamina and reticular lamina
What anchors epithelia to the underlying connective tissue?
Basal lamina
Can basal lamina be seen in light microscopy?
No, the basal lamina and reticular lamina appear as one layer. This is known as the basement membrane and this CAN be seen in light microscopy.
When is basal lamina classified as external lamina?
When it is not in epithelial tissue and completely surrounds the cell that it is found in
What is the function of hemidesmosomes? What is it connected to?
anchor basal cellular domain to the basal lamina. Connected to keratin filaments inside the cell
What are major components found in the basal lamina?
1) Collagen type IV2) Laminin 3) Proteoglycans
What types of cells are basal infoldings found in?
Cells involved in active transport of ions. These cells require ATP and therefore these infolding are closely associated with elongated mitochondria. Ex) Kidney cells
Function of simple squamous epithelium? Where is it found?
Gliding between inner body surfaces. Lines cavities (mesothelium) and vessels (endothelium)
What is mesothelium?
simple squamous epithelial tissue that lines body cavities
What is endothelium?
Simple squamous epithelial tissue that lines vessels (blood and lymph)
Function of simple cuboidal epithelium? Where is it found?
Forms secretory units (glands); found in SMALL ducts and ENDOCRINE glands
Function of simple columnar epithelium? Where is it found?
Absorption and secretion; found in GI tract. Brush border is present
What is the structure and function of stratified squamous epithelium? Where is it found?
Function: ProtectiveStructure: Basal cells are cuboidal, surface cells are squamous Where: Skin (keratinized), esophagus and vagina (both nonkeratinized)
What is the difference between keratinized and non-keratinized stratified squamous tissue?
Keratinized tissue have NO nuclei effect cells in top layer bc these are dead cells. This occurs in the skinNonkeratinized tissue have nuclei in the top layer but they are pyknotic (condensed) therefore inactive
Where is stratified cuboidal tissue located?
Large ducts of EXOCRINE glands
What is a goblet cell?
Unicellular gland that secretes mucus
Where is stratified columnar epithelium found?
Largest ducts of exocrine glands and parts of male urethra
What type of epithelium is found in the male urethra?
stratified columnar
What tissue type is this?
Stratified squamous epithelium
Where is pseudostratified columnar epithelium found? What are they often accompanied by?
respiratory tract; cilia
Where is transitional epithelium found? What are the two states it can be found in?
Lining distensible organs associated with urinary system (bladder)Relaxed stateDistended state
How does transitional epithelial appear in the relaxed state (non-distended)?
Many layers; the surface of cells bulge in the lumen and are frequently binucleated
How does transitional epithelial appear in the distended state?
Fewer layers; Outmost layer becomes squamous
What is the difference btw endocrine and exocrine glands?
Endocrine glands have no ducts and secrete their products into the blood or lymph system. Exocrine glands secrete their products onto body surfaces or lumen via a duct system.
What are unicellular glands?
One-cell glands (goblet cells)
How are multicellular glands classified?
1) Type of duct (simple vs compound) 2) Shape of secretory unit (tubular vs acinar/alveolar/saccular)3) Nature of secretion (mucous vs serous)4) Mode of secretion (merocrine, apocrine, Holocrine)
What is merocrine (eccrine) secretion?
when secretory product is released by exocytosis
What is the difference btw mucous and serous secretions?
Mucous is glycosylated proteins while serous is non-glycosylated
What types of secretions do merocrines perform?
Mucus or serous secretions
How do mucous cells appear on an H&E stain?
Pale cytoplasm and flattened nucleus near base of cell
How do serous cells appear on H&E stains?
Strongly stained cytoplasm (often apical granules) and a round or oval nucleus
What are mixed glands called that have mucous secretory units capped by serous cells?
Serous demilune
What is apocrine secretion?
from an exocrine cell involves the loss of cytoplasm as well as the secretory product
What is holocrine secretion?
The whole cell is the secretory product (sebaceous)
What are two types of benign epithelial tumors and where do they originate?
Papillomas —> surface epitheliumAdenomas —> Glandular epithelium
What are two types of malignant epithelial tumors and where do they originate?
Carcinomas—> surface epithelium Adenocarcinomas —> glandular epithelium
What is metaplasia?
Transformation of one type of epithelium Tori another, occurs under abnormal conditions