What Are Glands? The Anatomy and Function - Makpats

GLANDS

·   Definition: Epithelia are a group of tissues derived from all 3 embryonic germ layers, which are involved in absorption, secretion, selective diffusion and physical protection.

    Epithelia primarily involved in secretion are arranged into structures known as glands.

    Types of glands:

1. Exocrine

2. Endocrine

1. Exocrine Gland: 

It release their secretions onto an epithelia surface via a duct. It consists of 2 main parts.

(i) Secretory unit           (ii) A duct

- On the bases of shape, types of secretory unit of gland, types of exocrine glands are:

a. Tube shaped is referred as tubular.

b. Spherical shaped is referred as alveolar or acinar.

c. Both tubular and alveolar tubuloalveolor.

- On the basis of branched or unbranched duct, types of exocrine glands are:

a. An unbranched duct is known as simple. (Ex: Sweat gland)

b. Branched duct is known as compound.  (Ex: Pancreas)

Classification by Function: On the basis of their function exocrine glands are of 3 types

1. Serous Glands: Produce Serous fluid, a watery substance containing enzymes.

2. Mucous Glands: Involved in the production of mucus, a viscid (sticky) glycoprotein.

3. Mixed Glands: Comprised of both the above glands, secrete a mixed substance containing both serous fluid and mucus.


2. Endocrine Glands:

1.        Endocrine glands release their secretory products directly into the bloodstream, rather than via a duct.

2.        These glands are surrounded by a strong connective tissue capsule, which has fibrous extensions known as trabeculae.

These trabeculae provide internal support and give the gland a lobular appearance. Endocrine glands release secretions known as hormones, which travel via the bloodstream to reach their target cells, where they elicit functional changes.

The glands that make up the human of Endocrine system include:
1. Hypothalamus 
2. Pitutary gland
3. Thyroid
4. Parathyroid
5. Adrenal gland
6. Pineal gland
7. Reproductive gland (which include Overies and testes)
8. Pancrease

1. Hypothalamus is the part of the human brain. located superior and anterior to the brain stem and inferior to the thalamus. the hypothalamus contains special cells called Neurosecretory cells (neuron that secrete hormone).
  • Thyrotropin-releasing hormone (TRH)
  • Groeth hormone-releasing hormone (GHRH)
  • Growth hormone inhibiting hormone (GHIH)
  • Gonadotropin-releasing hormone (GnRH)
  • Corticotropin-releasing hormone (CRH)
  • Oxytocin
  • Anti-diuretic hormone (ADH)
2. Pitutary gland also known is hypophysis, is a small pea-size lump of tissue connected to the inferior portion of the brain. many blood vessels surrounded the PG to carry the hormone. Situated in a small depression in the sphenoid bone called Sella turcica. 
The PG is made of 2 structure: The posterior PG and  Anterior PG

Posterior Pitutary secrete 2 hormone. 
  • Oxytocin triggers uterine contractions during childbirth and the release of milk during breastfeeding.
  • Anti-Diuretic hormone(ADH) prevent water loss in the body by increasing the re-uptake of water in the kidneys and reducing blood flow to sweat glands.
Anterior Pitutary secrete 6 hormone.
  • Thyroid stimulating hormone(TSH), that stimulate the thyroid gland that produce the thyroxine(T4) and then triiodothyronin(T3) which stimulate metabolism of almostr every tissue in the body.
  • Follicle stimulating hormone(FSH),  stimulates the follicle cells of the gonands to produce gametes-Ova in female and sperm in male.
  • Adrenocorticotropic hormone(ACTH), stimulate the adrenal cortex, the outer paert of the adrenal gland, to produce its hormone.
  • Luteinizing hormone(LH), stimulate the gonads to produce the sex hormones- estrogens in females and testosterone in males.
  • Human growth hormone(HGH), affects many target cells throughout the body by stimulating their growth, repair and reproduction.