Lesson 1: Lining Epithelia Flashcards
What are the main functions of epithelial tissue?
Covers body surfaces, lines cavities, forms glands, protects, absorbs, secretes, and senses.
From which embryonic layers is epithelium derived?
Ectoderm, mesoderm, and endoderm.
What is the basement membrane?
A thin layer anchoring epithelial cells to underlying tissues.
Why is epithelial tissue avascular?
It relies on diffusion for nutrient and waste exchange.
What are the defining general features of epithelial tissue?
Cells are closely apposed, polarity, avascularity, presence of a basement membrane, and regenerative capability.
What is the importance of cell polarity in epithelial tissue?
It ensures directional secretion, absorption, and interaction with the environment.
How does epithelial tissue achieve its regenerative ability?
Through mitotic activity in the basal (germinal) layer.
What is the role of intercellular junctions in epithelial tissue?
To maintain structural integrity and regulate communication between cells.
What are simple epithelia mostly concerned with?
absorption, secretion and filtration
What are stratified epithelia mostly concerned with?
protection of the tissue/organ
Where is simple squamous epithelium typically found?
Lung alveoli, lumen of blood and lymph vessels (endothelium),
serosa (mesothelium), and Bowman capsule (kidney glomeruli)
What is the primary function of simple squamous epithelium?
Diffusion and filtration.
may secrete lubricating substances
Where is simple cuboidal epithelium located?
Kidney tubules, gland ducts, ovary surface, terminal bronchioles, retina.
What is the role of simple cuboidal epithelium?
Secretion and absorption.
What are some locations of simple columnar epithelium?
small intestine, stomach, uterine tubes, small bronchioles bronchi, gallbladder, excretory ducts.
How does simple columnar epithelium support absorption?
Through microvilli on the apical surface.
How does the simple squamous epithelium facilitate gas exchange?
Its thin structure allows efficient diffusion in alveoli.
What is the function of mesothelium derived from simple squamous epithelium?
To secrete lubricating fluid in serous membranes.
How does endothelium in blood vessels contribute to vascular function?
It reduces friction and regulates permeability. (simple squamous)
Why is simple cuboidal epithelium well-suited for kidney tubules?
It provides a balance of absorption and secretion.
Where is simple cuboidal epithelium found in endocrine glands?
In the follicles of the thyroid gland.
How does the structure of simple cuboidal epithelium aid in its function in glandular ducts?
Its cube-like shape offers structural support for secretory activity.
What is pseudostratified epithelium?
All cells rest on the basal membrane, but not all reach the apical surface.
Where is pseudostratified ciliated columnar epithelium found?
mucosa of the airways, urethra, epididymis, ear canal, big excretory ducts of glands
What is the function of cilia in pseudostratified epithelium?
To move mucus and trapped particles.
Why does pseudostratified epithelium appear stratified under a microscope?
Nuclei are positioned at varying heights, giving a false appearance of layering.
How does pseudostratified epithelium protect the respiratory tract?
Goblet cells secrete mucus, and cilia move debris-laden mucus out.
What is the significance of basal cells in pseudostratified epithelium?
They act as stem cells for regeneration.
What are some locations of simple columnar epithelium?
Intestinal lining, stomach, uterine tubes.
How does simple columnar epithelium support absorption?
Through microvilli on the apical surface.
What specialized features enhance the function of simple columnar epithelium in the intestines?
Microvilli for absorption and goblet cells for mucus secretion.
How does simple columnar epithelium in the uterine tubes assist reproduction?
Ciliated cells help transport the egg.
What is the role of simple columnar epithelium in the stomach?
Secreting mucus and enzymes for digestion.
What is the function of stratified squamous epithelium?
Protection against abrasion and pathogens.
Where is keratinized stratified squamous epithelium located?
Skin, particularly palms and soles.
How does non-keratinized stratified squamous epithelium differ?
It retains living cells in the uppermost layer and is found in moist areas like the esophagus and vagina.
Where is stratified cuboidal epithelium found?
Big gland ducts - Ducts of sweat glands and sebaceous glands, exocrine pancreas.
What is the role of stratified columnar epithelium?
Protection and secretion, found in large gland ducts and parts of the male urethra.
What are the protective advantages of keratinized stratified squamous epithelium?
It resists abrasion, dehydration, and microbial invasion.
Why does non-keratinized stratified squamous epithelium retain surface cell nuclei?
To maintain flexibility and moisture.
Where is stratified cuboidal epithelium commonly located?
In ducts of sweat and sebaceous glands.
What dual function does stratified columnar epithelium provide in glandular ducts?
Protection and mucus secretion.
Where is non-keratinized epithelium commonly found?
In the lining of the oral cavity, pharynx, larynx, esophagus, rectal canal, vagina, and cornea.
What is the main difference between keratinized and non-keratinized epithelium?
Keratinized epithelium has a layer of dead cells filled with keratin, while non-keratinized epithelium lacks this layer and has live, moist surface cells.
Where is keratinized epithelium commonly found?
Skin , Gingival epithelium, Tongue, Nasal epithelium
Where can stratified columnar epithelium be found?
larynx mucosa, male urethra, conjunctiva, big gland ducts
What is a key characteristic of transitional epithelium?
Cells change shape depending on organ distension.
Where is transitional epithelium found?
Urinary bladder, ureters, and renal pelvis, urethra.
What is the function of dome-shaped cells in transitional epithelium?
To allow stretching and protect underlying tissues.
How does transitional epithelium adapt to the stretching of the bladder?
Dome-shaped cells flatten when the bladder fills.
Why is transitional epithelium resistant to toxic effects of urine?
Its thick, protective cell layers and tight junctions prevent leakage.
What are binucleated cells in transitional epithelium?
Cells with two nuclei, enhancing their role in tissue integrity.
What are the layers of the epidermis in thick skin?
Basal layer, spinous layer, granular layer, lucidum, and corneum.
What is the role of keratinocytes?
To produce keratin for waterproofing and protection.
What causes the genetic disorder epidermolysis bullosa?
Mutations in keratin genes or laminin.
What What is the primary function of the stratum corneum?is the primary function of the stratum corneum?
Providing a tough, waterproof barrier.
How does the stratum basale support the epidermis?
It contains mitotic cells that regenerate the epidermis.
What is the clinical significance of dermal papillae in the skin?
They enhance the strength of the epidermis-dermis connection and increase surface area for exchange.
What is the role of melanocytes in protecting the skin?
They produce melanin, which absorbs UV radiation.
Describe the stratum corneum
25 or more layers of dead squamous cells still joined by desmosomes
eventually desmosomes break and cells flake off in a process called desquamation
Describe the stratum lucidum
Only in non-hairy or thick skin
Several layers of dead cells with indistinct boundaries
Describe the stratum granulosum
cells contain granules of keratin
Describe the spinous layer
cells are pushed upward and flatten out
Describe the basal layer
mitotic layer, continuously replaces epidermal cells, turnover rate between 25 to 50 days
What are microvilli, and what is their function?
Finger-like projections that increase the surface area for absorption.
What are cilia, and where are they found?
Motile structures on the apical surface, found in the respiratory tract and uterine tubes.
What are tight junctions?
Cell connections that prevent leakage between cells.
What are gap junctions?
Channels that allow communication between adjacent cells.
How do hemidesmosomes function?
By anchoring epithelial cells to the basement membrane.
How do Langerhans cells contribute to immunity?
By capturing and presenting antigens to T-cells.
What sensory function is associated with Merkel cells?
Detecting light touch and textures.
Why are keratinocytes the most abundant cells in the epidermis?
They form the structural framework and produce keratin.
What is the cause of blistering in epidermolysis bullosa simplex?
Fragility of basal cells due to keratin mutations.
What condition is associated with a breakdown of the intestinal epithelial barrier?
Inflammatory bowel disease.
What is the role of melanocytes in the epidermis?
Synthesis of melanin for pigmentation and UV protection.
Why is the shape of epithelial cells related to their function?
Flat cells facilitate diffusion, cuboidal cells support secretion/absorption, and columnar cells aid in specialized tasks.
How does the basement membrane support epithelial cells?
By providing structural support and separating them from connective tissue.
How does the loss of epithelial integrity contribute to chronic wounds?
It impairs the barrier and regenerative capabilities, leading to infections.
What happens when epithelial tight junctions are disrupted in the intestines?
Increased permeability can lead to leaky gut syndrome and inflammation.
Why is epithelial tissue highly regenerative compared to other tissues?
It is exposed to constant wear and damage, requiring rapid turnover.
How does the polarity of epithelial cells support directional secretion?
Apical domains release products into the lumen, while basal domains anchor cells.
Why is it important for glandular epithelium to form tight aggregates?
To concentrate secretory activity and prevent leakage.
What is the role of desmosomes in epithelial cells?
They anchor adjacent cells to resist mechanical stress.
How do integrins in the basement membrane support epithelial cells?
They mediate attachment and signal transduction.
What type of secretion is performed by goblet cells?
Mucus secretion to lubricate and protect surfaces.
How do microvilli in epithelial cells enhance absorption?
By significantly increasing the surface area.
What cells can be found in the epidermis?
Keratinocytes (95% of the cells) !!
Melanocytes (melanin synthesis) Langerhans cells (defence processes)
Merkel cells (tactile receptors)
