12. Epithelial Tissue Flashcards
What are the general characteristics of epithelial tissue?
- provide physical protection, permeability, secretion and sensation
- cellularity, pollarity, attachment, avascular, innervation, and regeneration
- rests on a basement membrane
- eipthelia that secrete are arranged as glands
Describe the polarity of epithelial tissue
- Apical Surface: faces exterior surface/lumen of an enclosed cavity/tube
- Basal Surface: rests on basement membrane, anchors cell to underlying conncetive tissue
- Lateral Surfaces: communicates/attaches to adjacent cells
What are the differences between tight junctions and gap junctions?
Tight/occluding junction:
- Impermeable, allows cells to function as a barrier
- Encircle cells near their most apical surface
- ↑ junctions = ↓ permeability
- Ptns: Occludins, claudins
Gap/communicating junction:
- Fluid-filled channels that connect apposed cells
- Mediate communication
- Connexin aggregates
What are the 3 types of anchoring junctions?
- Adherens: lateral adhesions involving cadherins that interact with actin filaments
- Desmosome: lateral adhesions involving cadherins that interact w/ intermediate filaments
- Hemidesmosomes: basal adhesions involving integrins that & intermediate filaments that anchor to basal lamina
What is the clinical relvance of a tight junction?
Bacteria that cause “food poisoning” target TJs in the intestine → impairs junctions → loss of tissuefluid into intestinal lumen
Helicobacter pylori causes gastric ulcers → bindsTJs in the stomach, increasing permeability
What is the clinical relevance of a desmosome?
Autoimmune disease pemphigus vulgaris → abnormal desmosome function → reduces cell- to-cell adhesion → blisters of oral mucosa
Describe the basement membrane
- Specialized sheet of extracellular material
- Located adjacent to basal domain
- Selective barrier between tissues permits diffusion of nutrients
Name and describe the apical specialization
Microvilli:
- Cytoplasmic processes containing an actin core
- Specialized for absorption
- ↑↑ surface area by 20-30x
- Number & shape correlate to the cell’s absorptive capacity
- 1mm long with up to 100k present on a single cell
What disease results from a loss of microvilli on absorptive cells in SI?
Celiac disease
Name and describe the apical specialization
Stereocilia:
- Microvilli of unusual length, long & less mobile
- Microtubule structure with actin core
- Increase surface area for absorption/secretion
Restricted location:
- Epididymis
- Hair cells of inner ear
Name and describe the apical specialization
Cilia:
- Long, highly motile structures containing internal arrays of microtubules
- Up to 10mm long & 300+ may be present
- Motile, Primary, & Nodal
What are the 3 types of cilia?
Motile: beat in a wave-like fashion to propel substances across the tissue
Primary: immotile, function as chemosensors, osmosensors, mechanosensors
Nodal: embryonic, have role in L/R axis determination
Name and describe the cell type
Simple Squamous
Location: lining of blood & lymphatic vessels (endothelium), lining of serous membranes (mesothelium), lining alveoli in lungs, loop of Henle in kidney, various ducts
Function: exchange, barrier, & lubrication
What is characeristic of endothelium?
lining of blood & lymphatic vessels
What is characteristc of mesothelium?
- lining of serous membranes (mesothelium)
- lining alveoli in lungs, loop of Henle in kidney, various ducts
Name and describe the tissue type
Simple Cuboidal
Location: kidney tubules, glands & associated ducts, terminal bronchioles, covering of the ovary
Function: Absorption, barrier, secretion
Name and describe the cell type
Simple Columnar
Location: auditory tubes, uterus, oviducts, stomach, SI/LI, gallbladder
Function: absorption & secretion
Name and describe the cell type
Pseudostratified Columnar Ciliated
Location: lining of nasal cavity, pharynx, trachea, bronchi
Function: absorption & secretion, debris & particulate movement
Name and describe the cell type
Urothelium
Location: urinary bladder, ureters, urethra
Function: barrier, distensible property
Name and describe the cell type
Nonkeratinized Strattified Squamous
Location: oral cavity, portions of the pharynx, esophagus, anus, vagina, urethra, cornea
Function: barrier & protection
Name and describe the cell type
Keratinized Stratified Squamous
Location: epidermis of the skin
Function: barrier & protection
Name and Describe the cell type
Stratified Cuboidal
Location: sweat glands & ducts, ovarian follicles, salivary gland ducts
Function: barrier & passageway
What is the difference between a mucous membrane and a serous membrane?
Mucous membrane: epithelial tissue that secretes mucus
- Lines many body cavities & tubular organs including the gut & respiratory passages
Serous membrane: epithelial tissue that lines internal body cavities
- Forms a smooth, transparent, two-layered membrane
- Lubricated by a fluid derived from serum
- Includes the peritoneum, pericardium, and pleura
- Mesothelium: simple squamous epithelium that comprises part of a serous membrane
What are the 2 classes of glands?
Glands are classified as exocrine (secretion) or endocrine (blood) according to how their products are released
What type of gland is depicted below?
Unicellular Glands:
- Simplest in structure
- Single, secretory cells distributed among non-secretory cells
What cell type is highlighted in red?
Goblet cell: mucus-secreting cell lining the intestines & respiratory tract
What are the general characteristics of exocrine glands?
Multicellular glands comprised of secretory cells grouped as an acinus
- Product is secreted into a system of ductsfor release
Parenchyma: functional tissue of an organ, does not include CT & other supporting tissues
Secretory units are supported by a stromaof connective tissue
- Septa, partitions that separate gland into lobules
- May enclose entire gland as a capsule
What type of acini is depicted?
Serous acini
What type of acini is depicted?
Mucous Acini
What type of acini is depticed?
Mucoserous Acini
What type of gland is depicted?
Parotid gland
What type of gland is depicted?
Sublingual gland
What type of gland is depicted?
Submandibular gland
Name and describe the gland type
Merocrine Gland
Secretion is delivered in membrane-bound vesicles to apical surface & undergo exocytosis
Name and describe the gland type
Holocrine Gland
Secretion accumulates w/in cell → apotosis
Secretion & cell debris are released
Name and describe the gland type
Apocrine gland
Release of the apical portion of the cell, surrounded by cytoplasm w/in a plasma membrane
