الأسبوع 4 · الفصل الثاني «التنسيق الهرموني» (١): الجهاز الصماوي والهرمونات واكتشافها وهرمونات النبات (الأوكسينات) وخصائص الهرمونات وأنواع الغدد في الإنسان والغدة النخامية وهرموناتها ومقارنة التنظيم الهرموني بالعصبي · 3 دروس
2
Glands in the body and the pituitary, the master gland
Biology Sec 3 Term 1, Chapter 2: pp. 23–29
GoalTell exocrine, endocrine and mixed glands apart, and describe where the pituitary gland lies and its two parts.
New words
exocrine gland · a gland with a duct that carries its secretion into a body cavity or to the outsidemixed gland · a gland with a part that sends secretions along a duct and a part that releases hormones into the bloodpituitary gland · the master gland, below the brain, that controls most other endocrine glandshypothalamus · the part of the brain joined to the pituitary; its nerve cells make two of the pituitary’s hormones
Explanation
The human body has three kinds of gland. An exocrine gland has a secreting part and a duct, or a system of ducts, that carries the secretion either into a cavity inside the body, as in the salivary and digestive glands, or to the outside, as in the sweat glands. An endocrine gland has no duct and releases hormones directly into the blood. A mixed gland has both: the pancreas sends pancreatic juice along a duct to the duodenum and also releases hormones into the blood. The pituitary gland is called the master gland because it controls the work and the secretions of most of the other endocrine glands. It lies beneath the brain and is joined to the hypothalamus. It has two parts. The adenohypophysis, the glandular part, is made of the anterior lobe and the middle lobe. The neurohypophysis, the nervous part, is made of the posterior lobe and the infundibulum, a stalk that joins the gland to the brain.
Worked examples
Kind
Duct?
Where the secretion goes
Example
Exocrine
yes
into a body cavity or to the outside
salivary gland, sweat gland
Endocrine
no
straight into the blood
pituitary gland
Mixed
both
duct and blood
pancreas
The three kinds of gland compared.
Classify each. A gland in the skin that makes sweat and sends it to the surface through a duct: exocrine. A gland in the stomach wall that sends digestive juice into the stomach: exocrine. The pancreas: mixed, because it also makes hormones. The pituitary: endocrine.
hypothalamus in the brain→pituitary gland below it→other endocrine glands→the body’s functions
A chain of command. The hypothalamus is joined to the pituitary, and the pituitary controls other glands.
Class activity
Sort the glands, with a grown-up. Write these names on six slips of paper: sweat glands, salivary glands, glands that make gastric juice, the thyroid, the pituitary, the pancreas. Make three piles labelled exocrine, endocrine and mixed. Put each slip on a pile and write one reason beside it. Then draw the pituitary under a simple brain, label its two parts, and mark where the stalk joins the brain.
Practice
1
Give one difference between an exocrine gland and an endocrine gland.
An exocrine gland has a duct, but an endocrine gland has none and releases its hormones into the blood.
2
Which gland is mixed, and what are its two kinds of secretion?
The pancreas. It makes pancreatic juice, sent along a duct to the duodenum, and hormones, released into the blood.
3
Why is the pituitary called the master gland?
Because it controls the work and secretions of most of the other endocrine glands.
4
Name the two parts of the neurohypophysis.
The posterior lobe and the infundibulum, the stalk joining the gland to the brain.
