Glands histology

distinguish epithelial tissue which is glandular from that which has a barrier

outline the classification of glands based on their morphology

apical secretion: these glands secrete their content onto the free epithelial surface and are classified as EXOCRINE glands. they are derived From an Epithelial Layer in the embryo and retain their connection with the epithelial surface via a drainage duct

Basal secretion: These glands have lost their connection with the epithelial surface and secrete their contents into underlying

connective tissue, where the secretions pass into tissue fluid and blood vessels, and are classified as ENDOCRINE GLANDS. This type of secretory product is called a hormone.

describe functional anatomy of select glands

simple exocrine glands: secretory unit drains directly (with or without a duct) onto epithelial surface. it may branch, but if it’s drained by a single duct, it’s classified as simple. types: sebaceous glands, which have no duct and secretory unit opens directly into a hair follicle. OR sweat glands, each secretory unit drains via its own duct onto the epidermis.

Compound: more common. branching duct system; ducts from many secretory units join to form a large single duct which opens onto epithelial surface. This is a much better design because the epithelial barrier is weakened at only one point. Also, a single long duct makes it possible to ‘park’ the secretory units somewhere convenient; e.g., parotid salivary glands, which lie ventral to the external ear

Mucous exocrine glands

glands are made up entirely of mucous cells. they secrete proteoglycans (mucus or mucin, a lubricating secretion) and form tubular secretory units made up of columnar epithelial cells that are pale-staining. mucus store flattens the nucleus towards the base of the cell

Serous exocrine glands

vast majority of proteins secreted by this type of gland are enzymes. a minority serve other purposes such as nutritive proteins secreted by mammary glands. serous glands are ALVEOLAR (aka acinar) secretory units consisting of pyramidal-shaped cells which are strong-staining and have round, unflattened nuclei. ex: parotid gland.

Mixed exocrine glands

some exocrine glands consist of a mixture of mucous and serous glands (ex: mandibular salivary gland) and are compromised of tubular and alveolar secretory glands. some secretory units have some mucus tubular units Capped by crescent-shaped serous cells (serous demilunes)

thyroid gland

produces T3 and T4 (thyroxine) and regulate basic metabolic rate. these hormones are lipophilic, so on formation, they diffuse out of the cell and into their target cells. TGB (thyroglobulin) secretes more t3 and t4 when needed.

Thyroid gland cells are organised into follicles- hollow balls of cuboidal epithelial cells. TGB is secreted from the apical surface of the cells into the follicle lumen (i.e., as an EXOCRINE secretion). When more thyroid hormones are

required by the body, the cuboidal epithelial cells take up some of the precursor protein and break it down (by

phagocytosis) to release the active hormones, T3 and T4, which diffuse out into the capillary beds in the thyroid gland to be distributed throughout the body

adrenal gland

adrenal medulla: centre of gland derived from sympathetic neurons that have given up their neuronal phenotype; their neurohormone is secreted into blood. The cells secrete mainly adrenaline and almost no noradrenaline, and are under nervous control.

adrenal cortex: outer layer of gland containing cells that synthesise and release steroid hormones.

recognize glandular tissue under the microscope by applying this basic classification, being able to distinguish between exocrine mucous and serous glands and a limited number of endocrine glands