Define the term gland
Specialised cell, group of cells, or organ of endothelial origin that selectively removes materials from the blood, concentrates or alters them, and secretes them for further use in the body or for elimination from the body
How are glands classified by the destination of secretion?
1) Exocrine - glands secretes into ducts
2) Endocrine - glands are 'ductless', secrete directly into bloodstream or lymphatic vessels
Name three types of secretory methods
Describe holocrine secretion
Holocrine secretions are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the lumen
Describe merocrine secretion
Merocrine secretions are those that are secreted by exocytosis. There is NO loss of cell and is the most common form of secretion
Describe apocrine secretion
Relating to or denoting multicellular glands which release some of their cytoplasm in their secretions, especially the sweat glands associated with hair follicles in the armpits and pubic regions.
Describe the mechanism of endocytosis
- Endocytosis is the process of engulfing material initially outside the cell.
- Vesicle engulfed into the cell by fusing with plasma membrane and budding off in the cytoplasm
Why is glycosylation of newly synthesised proteins in the Golgi so important?
O-linked glycosylation of proteins, by glycosyl transferase, using the addition of complex branching sugars, produces glycoproteins that form the glycocalyx on the cell surface membrane Glycocalyx is needed for:
- Adhesion to substrates and neighbouring cells
- Mobility of cells
- Communication with neighbouring cells
Name three secretions from the exocrine pancreas
- Pancreatic amylase
Describe simple mechanisms that control secretions
There are 4 main mechanisms
1) Nervous control - Adrenaline rerelease from adrenal medulla stimulated by sympathetic nervous stimulation
2) Endocrine control - ACTH stimulates the cortex of the adrenal gland to secrete cortisol
3) Neuro-endocrine control - Nervous cells of the hypothalamus control ACTH secretion from the anterior pituitary
4) Negative feedback chemical mechanism - Inhibitory effect of high T3 and T4 levels on TSH synthesis by the anterior pituitary gland
What does a mucous membrane consist of?
1) An epithelium (type depending on site) lining the lumen of a tube
2) An adjacent layer of connective tissue often referred to as the lamina propria
3) In the alimentary tract, a third layer consisting of smooth muscle cells referred to as the muscularis mucosae
What does a serous membrane consist of?
These are thin two-part membranes that line certain closed body cavities. They envelop the viscera (hand in balloon)
1) A simple squamous epithelium (mesothelium), which secretes a watery lubricating fluid
2) A thin layer of connective tissue which attaches to epithelium to adjacent tissues (also carries blood vessels and nerves)
Name an exocrine gland
- Goblet cells
- Parotid glands
- Submandibular glands
Name an endocrine gland
- Thyroid gland
- Parathyroid glands
- Adrenal glands
Describe the structure of the alimentary tracts
1) The mucosa (innermost layer)
2) The submucosa (areolar connective tissue)
3) Muscularis externa (peristalsis)
4) The serosa (serous membrane)
Describe the structure of the oesophagus
1) Non-keratinised stratified squamous epithelia
2) Lamina propria - loose connective tissue bearing blood and lymph vessels, some smooth muscle and many cells of the immune system
3) Muscularis mucosa - the thin layer of smooth muscle cells
4) Submucosa - subtending layer of connective tissue containing mucus secreting glands
5) Muscularis externa - Smooth muscle layers (inner circular, outer longitudinal), which move food via peristalsis
6) Adventitia - thin outermost layer of connective tissue (no peritoneal enfolding of this portion of the GI tract)
Describe the structure of the stomach
1) Epithelium - Simple columnar epithelia for absorption
2) Gastric mucosa - secretes acid, digestive enzymes and gastrin
3) Muscularis mucosa
5) Muscularis externa - three layers (oblique, circular and longitudinal) of smooth muscle
6) Rugae - Folds of the gastric mu
What are the layers of the tracheal mucosae?
1) Pseudostratified ciliated epithelia
3) Fibroelastic membrane and tracheal muscle
4) C-shaped Hyaline cartilage
What are the layers of the bronchioles?
2) Smooth muscle
Where are the plicae circulares found?
How many layers of muscularis externa are found in the bladder?
3 - inner circular, outer longitudinal and oblique