BIOS 251 Week 4 Discussion: Histology and Tissue Types – Graded An A+

BIOS 251 Week 4 Discussion: Histology and Tissue Types – Graded An A+ Question: • Classify the major exocrine glands with respect to their structure, their modes of secretion, and give clear examples of where each class of gland would be found in the human body. Answer: A gland is a functional unit of cells that work together to create and secrete these substances. Exocrine glands are comprised of an acinus and a duct with different cell types, respectively and secrete substances into a ductal system to an epithelial surface. Anatomy of exocrine system glands includes: • Acinus: Tiny sacs containing cells of exocrine system secretions that the duct hasn’t yet released. An acinus may house many different types of cells depending on the type of secretion the duct is responsible for. • Duct: Passageway that transports cell secretions to the inner surfaces of organs throughout your body. Exocrine secretions form in the acinus, a small cluster of cells at the origination of glandular ducts. Exocrine glands subclassify into subtypes based on the method of secretion, the compound produced, or the shape of the gland. While the duct functions primarily to transport glandular secretions, the acinus is responsible for the production of glandular secretions. The function of each depends on the organ in your body they’re associated with. The main purpose of all exocrine glands is to make and release substances to assist your body in some way. They help the body: • Digest food. • Absorb nutrients. • Protect the inner lining of the organs. • Control body temperature. • Lubricate hair and skin. Typical cell types within the acinus include serous, mucinous, or sebaceous. • Serous cells secrete an isotonic fluid that contains proteins such as enzymes. Salivary glands are made up of serous cells to a large extent. • Mucinous glands secrete mucus (Secrete mucins which mixes with water to form mucous), “Brunner glands in the duodenum”. • Sebaceous glands secrete sebum, an oily compound. “Face, scalp, groin, and armpits”. Exocrine glands (Modes of secretion) Your exocrine glands release their substances in different ways. The three main ways exocrine glands can secrete their substances are: • Merocrine glands: Release their substances through a process called exocytosis. With exocytosis, the cells aren’t damaged at all. Eccrine sweat glands and salivary glands. • Apocrine glands: make buds of the cell membranes, which break off into the duct. This causes them to lose part of the membrane in the process - Secretions are released via a loss of the apical cytoplasm. Mammary glands and ceruminous (wax) glands lining the external ear canal. • Holocrine glands: The cell membrane bursts to release its substance. Cells increase in size as secretion occur - Secretions via loss of the entire cell. Sebaceous glands “oil glands”. Different types of exocrine glands: • Sweat glands: create and secrete sweat. A type of sweat gland called eccrine sweat glands covers almost your entire body surface. These sweat glands produce clear, non- oily sweat that helps control your body temperature. • Sebaceous glands: are also on your skin. But they open into hair follicles. Sebaceous glands secrete sebum. Sebum is an oily substance that lubricates and protects hair and skin. • Salivary glands: create and secrete saliva. Salvia helps us chew, swallow and digest food. It also helps lubricate and protect the inner lining of tissues. • Lacrimal glands: Tear glands – located above your upper eyelids. They create and secrete a fluid that gets into the eyes every time we blink. This fluid helps keep eyes moisturized. • Mammary glands: produce milk. • Ceruminous glands: Glands in your ears. They help produce ear. wax (cerumen). Ear wax protects your ears from physical damage and infection. • Stomach glands: Release enzymes that help break down food. They also help the body absorb important nutrients. • Brunner glands: Located in the first part of the small intestine “duodenum”. They produce mucus that protects the duodenum from stomach acid. Also help the body digest food and absorb nutrients. • Liver and Pancreas have dual roles. o Exocrine glands” Liver secretes bile through ducts into the gastrointestinal tract. Pancreas secretes pancreatic juices through ducts into the gastrointestinal tract. o But liver and pancreas are also considered endocrine glands. They also secrete hormones directly into your bloodstream. References • Young B, O’Dowd G, Woodford, P. Epithelial tissues. In: Wheater's Functional Histology, A Text and Colour Atlas, 6th ed. Churchill Livingstone, an imprint of Elsevier • Aranda-Gutierrez A, Diaz-Perez HM. Histology, Mammary Glands. ( • Freeman SC, Malik A, Basit H. Physiology, Physiology, Exocrine Gland. ( • Hodge BD, Sanvictores T, Brodell RT. Anatomy, Skin Sweat Glands. ( • Hoover E, Aslam S, Krishnamurthy K. Physiology, Sebaceous Glands. ( StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Accessed 5/6/2022. • Sedano J, Swamy R, Jain K, Gupta S. Brunner's gland hamartoma of the duodenum. ( • Freeman SC, Malik A, Basit H. Physiology, Exocrine Gland. [Updated 2021 Sep 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: