Chapter 5

• There are 2 types of glands


  Exocrine glands and endocrine glands.
• Exocrine glands:

  • Are glands with ducts
  • The juices they secrete contain chemicals like enzymes.
  • Examples: gastric glands, salivary glands, sweat glands, etc.


  Endocrine glands:

  • Are ductless glands
  • They secrete hormones (the hormones are secreted directly into the blood)
• Hormonal activity:

  1. Synthesis of hormones by endocrine gland.
  2. Release of hormones into the blood.
  3. Transportation of hormones to their target by blood.
  4. Fixation of hormones on their receptors (to form hormone-receptor complex.)
  5. Response of the target organ.

  
• Hormonal activity is characterized by:

  1. Organ communication
  2. Blood communication
  3. Chemical communication
• Organ communication: it indicates the  control that is done by the endocrine gland on its target.
• Blood communication: it shows the role of the blood between the endocrine gland and it's target.
• Chemical communication: it is achieved by chemicals (hormones) carried by blood.
• Insulin is a hormone that is secreted by the B cells of the pancreas in response to high level of glucose in the blood. The role of insulin is to lower the level of glucose in the blood.


  Glucagon is a hormone that is secreted by A cells of the pancreas in response to low level of glucose in the blood. The role of glucagon is to higher the level of glucose in the blood.
• Targets Of insulin:

  Different body organs are said to be the targets of insulin like the liver, muscles and the cells of adipose tissue.

  Insulin stimulates the uptake (absorption) of glucose by the cells of these target organs so that the excess glucose is stored in the form of glycogen in the liver and muscles or is stored in the cells of the adipose tissue in the form of fats.
• Diabetes could be due to:

  1. insufficient secretion of insulin by the B cells
  2. the secretion of abnormal nonfunctional insulin or
  3. a problem in the receptors.
• Insulin is secreted under a hyperglycemian condition to lower down the sugar levels so it has a hypoglycemian role.


  Glucagon is secreted under hypoglycemian condition to higher up the sugar levels so it has a hyperglycemian role.
• There is organ communication between the pituitary gland and the thyroid gland such that the pituitary gland stimulates the release of thyroid hormone by the chemical (T.S.H) which is secreted into the blood.


  T.S.H is a factor affecting the production of T3