Epithelia & Skin Flashcards
What are the characteristics of epithelial tissue?
- Epithelial Cells: Have a specialised surface (apical/luminal pole of cells)
1b. Junctional complees (little extracellular substance) - Basement membrane: underlying basal pole of cells
- Connective Tissue layer: regularity of cell arragement and diffusion of nutrients from underlying connective tissue layer
3b. Nerves
3c. Capillaries
What is the location and function of Simple Squamous Epithelium cells?
They are located in air sacs of lungs and the lining of the heart, blood vessels and lymphatic vessels.
Allow materials to pass through by diffusion and filtration and secretes lubricating substances
What is the location and function of Simple Cuboidal Epithelium?
They are located in ducts and secretory portions of small glands and in the kidney tubules
Secrete and absorb substances.
What is the location and function of Simple Columnar Epithelium?
They are located in cilliated tissue and in bronchi, uterin etubes and uterus.
They absorb substances; also secrete mucous and enzymes
What is the location and function of Pseudostratified Columnar Epithelium?
They are found in ciliated tissue lining the trachea and much of the upper respiratory tract.
Secrete mucus and ciliated tissue moves mucus
What is the location and function of Stratified Squamous Epithelium?
Lines the esophagus, mouth and vagina.
Provides physical protection against abrasion, pathogens and chemical attack.
What is the location and function of STRATIFIED CUBOIDAL EPITHELIUM?
They are found in sweat glands, salivary glads and the mammary glands.
They are a protective tissue.
What is the location and function of Stratified Columnar Epithelium?
It is located in the male urethra and the ducts of some glands.
It protects and secretes substances
What is the location and function of Transitional Epithelium?
It is located in the bladder, urethra and the uterus.
It allows the urinary organs to expand and stretch.
What is the significance of Stratified cuboidal & stratified columnar epithelium?
They are both uncommon tissue types and found in ducts of large glands.
E.g. Salivary glands
What is a gland and what are the 2 secretory types?
Cells that produce exocrine or endocrine secretions.
Whats the difference between exocrine and endocrine glands?
Exocrine glands release their secretions into passageways called ducts that open onto an epithelial surface (e.g. salivary gland)
Whilst
Endocrine glands release their secretions into the interstitial fluid. (e.g. thyroid)
What are the methods of secretion for exocrine glands? (1) (Salivary glands)
- Merocrine: The product is released from secretory vesicles by exocytosis. Most common mode of exocrine secretion.
e. g. Mucin is a merocrine secretion that mixes with water to form mucus. It is a lubricant, protective barrier and a sticky substance that traps microorganisms. The salivary gland secretions coat food and reduce friction during swallowing.
What are the methods of secretion for exocrine glands? (2)
Apocrine secretion: involves the loss of cytoplasm as well as the secretory product. The apical portion of the cytoplasm becomes packed with secretory vesicles and is then shed.
e.g. Milk production in mammary glands involves a combination of merocrine and apocrine secretions.
What are the methods of secretion for exocrine glands? (3)
Holocrine secretion: Destroys the gland cell. The entire cell becomes packed with secretory vesicles and then burst, releasing its secretions but killing the cell.
e.g. Sebaceous glands, associated with hair follicles, produce an oily hair coating by means of holcrine secretions.
What are the structural classifications of Exocrine glands?
Simple & Compound
Tubular & Aveolar
- Compound Tubuloalveolar = salivary glands
Exocrine glands can be categorised based on the types of secretions produced. What are they?
- Serous glands: secrete a watery solution that contains enzymes.
E.g. The parotoid salivary glands
- Mucous glands: secrete mucins that hydrate to form mucus.
E.g. The sublingual salivary glands & submucosal gland of the small intestine
- Mixed exocrine glands: contain more than one type of gland cells; they may produce two different exocrine secretions.
E.g. The submandibular salivary glands are mixed exocrine glands
What are the 3 pairs of salivary glands and what are there features? (1)
- The large parotid salivary gland:
Compound acinar glands
lie inferior to the zygomatic arch deep to the skin covering the lateral and posterior surface of the mandible.
Each gland has an irregular shape
They extend from the mastoid process of the temperal bone across the outer surface of the master muscle.
Produces a serous secretion containing large amounts of salivary amylase (breaks down starch/complex carbs)
The secretions of each gland are drained by the parotid duct; which empties into the vestibule at the second upper molar.
What are the 3 pairs of salivary glands and what are there features? (2)
The Sublingual salivary gland: Covered by mucous membrane of the floor of the mouth.
compound tubuloacinar glands
Produces a mucous secretion that acts as a buffer and lubricant.
Numerous sublingual ducts open along either side of the lingual frenulum.
What are the 3 pairs of salivary glands and what are there features? (3)
The Submandibular salivary gland: Lies along the inner surface of the mandible within a depression called the mandibular groove.
compound tubuloacinar glands
Cells secrete a mixture of buffers, glycoproteins called mucins, and salivary amylase.
The submandibular ducts open into the mouth either side of the lingual frenulum immediately posterior to the teeth.
What controls salivary secretions?
The autonomic nervous system controls salivary secretions.
Each gland has a parasympathetic and sympathetic innervation.
The parasympathetic outflow originates in the salivatory nuclei of the medulla oblongata and synapses in the submandibular and otic ganglia.
Any object in the mouth can trigger a salivary reflex. Stimulates receptors monitored by the trigeminal nerve (N V) or taste buds innervated by cranial nerve VII, IX or X.
Parasympathetic stimulation speeds up secretions by all the salivary glands = more saliva production.
Sympathetic might stimulate thick saliva production
What are the minor salivary glands?
Lingual, Labial, Buccal, Molar & Palatine
How to identify salivary glands…
- Sublingual: Pale staining mucus cells
- Paratoid: Dark staining serous cells, completely serous gland
- Submandibular: Mixed serous/mucous acini
How to classify epithelium…
Number of layers
Shape of cells (luminal surface specialisations)
