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Questions and Answers
What is the primary function of covering epithelia?
What is the primary function of covering epithelia?
- Secretion of hormones
- Transmission of nerve impulses
- Protection of underlying tissues (correct)
- Contraction and movement
What is unique about the structure of epithelial tissue?
What is unique about the structure of epithelial tissue?
- It is composed of loose connective tissue
- It has closely aggregated polyhedral cells (correct)
- It has a large number of blood vessels
- It has a large amount of extracellular substance
What is the function of glandular epithelia?
What is the function of glandular epithelia?
- To absorb nutrients
- To provide sensation
- To secrete hormones (correct)
- To protect underlying tissues
What is the purpose of the basal lamina?
What is the purpose of the basal lamina?
What is the main component of the lamina densa?
What is the main component of the lamina densa?
What connects integrins on the basal surface of epithelial cells to the type IV collagen network?
What connects integrins on the basal surface of epithelial cells to the type IV collagen network?
What is the function of neuroepithelial cells?
What is the function of neuroepithelial cells?
What is unique about the nutrition of epithelial cells?
What is unique about the nutrition of epithelial cells?
What type of collagen is found in anchoring fibrils that link the basement membrane to the interstitial matrix?
What type of collagen is found in anchoring fibrils that link the basement membrane to the interstitial matrix?
Which of the following proteins do integrins on the fibroblast cell surface interact with?
Which of the following proteins do integrins on the fibroblast cell surface interact with?
What is the name of the surface of epithelia that rests on the basal lamina?
What is the name of the surface of epithelia that rests on the basal lamina?
What is the classification of epithelia based on the number of layers?
What is the classification of epithelia based on the number of layers?
Which of the following is NOT a classification of epithelia based on the shape of cells?
Which of the following is NOT a classification of epithelia based on the shape of cells?
What is the name of the type of epithelium that is found in the urinary tract?
What is the name of the type of epithelium that is found in the urinary tract?
What type of epithelium is found in the respiratory passages?
What type of epithelium is found in the respiratory passages?
What is the main function of tight junctions in epithelial cells?
What is the main function of tight junctions in epithelial cells?
What is the function of microvilli in epithelial cells?
What is the function of microvilli in epithelial cells?
What is the function of gap junctions in epithelial cells?
What is the function of gap junctions in epithelial cells?
What type of glandular epithelium is found in the stomach?
What type of glandular epithelium is found in the stomach?
What is the function of cilia in epithelial cells?
What is the function of cilia in epithelial cells?
What is the function of the glycocalyx in epithelial cells?
What is the function of the glycocalyx in epithelial cells?
What is the function of basal striations in epithelial cells?
What is the function of basal striations in epithelial cells?
What is the characteristic of holocrine glands?
What is the characteristic of holocrine glands?
What is the characteristic of apocrine glands?
What is the characteristic of apocrine glands?
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Study Notes
Epithelial Tissue
- Covers body surfaces and lines body cavities
- Made up of special cells that enable it to fulfill many functions:
- Protection
- Secretion
- Excretion
- Found in various parts of the body, including:
- Respiratory passages
- Oral cavity
- Skin
- Digestive tract
- Heart and blood vessels
- Peritoneum
- Pericardium
- Urinary tracts
- Glands
- Lymph vessels
Characteristics of Epithelial Tissue
- Composed of closely aggregated polyhedral cells
- Almost no or no extracellular substance
- Epithelial cells are separated from connective tissue by the basal lamina
- No blood vessels; nutrition is from connective tissue
Functions of Epithelia
- Covering epithelia:
- Covering of surfaces and lining of cavities
- Protection of covered tissue
- Absorption (intestines, proximal tubules of kidney)
- Glandular epithelia:
- Secretion (exocrine glands)
- Neuroepithelial cells:
- Sensation (olfactory epithelium, taste buds)
Basal Lamina
- Selective barrier between connective tissue and epithelium
- Adhesion of connective tissue and epithelium
- Supports cells
- Components of basal lamina:
- Lamina lucida (rara)
- Lamina densa
- Reticular lamina
Polarity of Epithelia
- Apical surface
- Basal surface: rests on basal lamina
- Lateral surface
Classification of Epithelia
- According to number of layers:
- Simple
- Stratified
- Pseudostratified
- According to shape of cells:
- Squamous
- Cuboidal
- Columnar
Simple Epithelia
- Simple squamous epithelium:
- Endothelium, mesothelium, air sacs of the lungs (alveoli)
- Simple cuboidal epithelium:
- Proximal and distal renal tubules
- Simple columnar epithelium:
- Stomach, small and large intestine, oviduct
Stratified Epithelia
- Stratified squamous epithelium:
- Keratinized (skin)
- Non-keratinized (oral cavity, vagina)
- Stratified cuboidal epithelium:
- None mentioned
- Stratified columnar epithelium:
- None mentioned
- Transitional epithelium:
- Urinary bladder, ureter
Intercellular Junctions
- Tight junction (zonula occludens)
- Desmosome (macula adhaerens)
- Hemidesmosome
- Gap junction (nexus)
Epithelial Surfaces Modifications
- Microvilli:
- Extensions of cytoplasm
- Increase surface area for absorption
- Cilia:
- Long projections
- Motile
- Enable removal of material over epithelium
- Stereocilia:
- Long microvilli (in epididymis and ductus deferens)
- Flagella:
- Similar structure to cilia
Glandular Epithelia
- Function: secretion of products used in other parts of the organism
- Types of exocrine glands:
- Holocrine
- Apocrine
- Merocrine
- Unicellular glands:
- Mucous secretion
- Multicellular glands:
- Branched
- Compound
- Tubule
- Acini
- Tubuloacini
Sensory Epithelia
- Enables sensation (olfactory epithelium, taste buds)
Nutrition of Epithelia
- No blood vessels in epithelia
- Nutrients and precursors of products diffuse from connective tissue across the basal lamina to epithelial cells
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