The Endocrine System
Nursing Department
1
At the end of this lecture, you will be able to:
Distinguish between exocrine and endocrine glands.
Describe the locations and function of :
hypothalamus and pituitary gland, thyroid gland, parathyroid
glands, adrenal glands, pancreatic islets.
Describe the location, hormones, and functions of the male and female
gonads, pineal gland and role of the thymus in immunity.
OBJECTIVES
2
INTRODUCTION
The body contains two kinds of glands:
1. Exocrine glands:
include sudoriferous(sweat), sebaceous (oil), mucous, and digestive
glands.
2. Endocrine glands:
include the pituitary, thyroid, parathyroid, adrenal, and pineal glands.
3
In addition, several organs and tissues are not exclusively classified as
endocrine glands but contain cells that secrete hormones.
These include the hypothalamus, thymus, pancreas, ovaries, testes,
kidneys, stomach, liver, small intestine, skin, heart, adipose tissue, and
placenta.
Cont.
4
5
For many years, the pituitary gland or hypophysis was called the “master”
endocrine gland because it secretes several hormones that control other
endocrine glands.
We now know that the pituitary gland itself has a master.
Hypothalamus and Pituitary Gland
6
• The pituitary gland is a pea-shaped structure that measures 1–1.5 cm (0.5
in.) in diameter and lies in the hypophyseal fossa of the sella turcica of the
sphenoid bone.
• It attaches to the hypothalamus by a stalk.
Cont.
7
And has two anatomically and functionally separate portions:
The anterior pituitary
the posterior pituitary.
The anterior pituitary (anterior lobe), also called the adenohypophysis
(adeno- = gland; -hypophysis = undergrowth), accounts for about 75% of
the total weight of the gland and is composed of epithelial tissue.
Cont.
8
The anterior pituitary consists of two parts in an adult: The pars distalis is
the larger portion, and the pars tuberalis.
The anterior pituitary secretes hormones that regulate a wide range of
bodily activities, from growth to reproduction.
Five types of anterior pituitary cells:
1. Somatotrophs.
2. Thyrotrophs.
3. Gonadotrophs.
4. Lactotrophs.
5. Corticotrophs.
Cont.
9
The posterior pituitary (posterior lobe), also called the
neurohypophysis (neuro- = nerve), is composed of neural tissue.
It also consists of two parts: the pars nervosa and the pars
intermedia.
cont.
10
Thyroid Gland
The butterfly-shaped thyroid gland is located just inferior to the
larynx (voice box).
It is composed of right and left lateral lobes, one on either side of
the trachea that are connected by an isthmus(IS-mus = a narrow
passage) anterior to the trachea.
About 50% of thyroid glands have a small third lobe, called the
pyramidal lobe.
11
It extends superiorly from the isthmus.
The normal mass of the thyroid is about 30 g (1 oz).
two hormones secreted from thyroid: thyroxine which is also
called tetraiodothyronine (T4)and triiodothyronine (T3)
cont.
12
13
Partially embedded in the posterior surface of the lateral lobes of the
thyroid gland are several small, round masses of tissue called the
parathyroid glands (para- = beside). Each has a mass of about 40
mg (0.04 g).
Usually, one superior and one inferior parathyroid gland are attached
to each lateral thyroid lobe, for a total of four.
Parathyroid Glands
14
Parathyroid hormone is the major regulator of the levels of:
Calcium(Ca2+)
Magnesium (Mg2+)
Phosphate (HPO42−)
Ions
In the blood.
Cont.
15
16
Adrenal Glands
The paired adrenal glands or suprarenal glands, one of which lies
superior to each kidney in the retroperitoneal space, have a flattened
pyramidal shape.
In an adult, each adrenal gland is 3–5 cm in height, 2–3 cm in width, and
a little less than 1 cm thick, with a mass of 3.5–5 g, only half its size at
birth.
17
The adrenal glands differentiate into two structurally and functionally
distinct regions:
Adrenal cortex: Is subdivided into three zones, each of which
secretes different hormones.
Adrenal medulla: The inner region of the adrenal gland, the
adrenal medulla, is a modified sympathetic ganglion of the
autonomic nervous system (ANS).
The two major hormones synthesized by the adrenal medulla are
epinephrine (ep′-i-NEF-rin) and norepinephrine.
cont.
18
19
The pancreas (pan- = all; -creas = flesh) is both an endocrine gland
and an exocrine gland.
A flattened organ that measures about 12.5–15 cm (5–6 in.) in length,
the pancreas is located in the curve of the duodenum, the first part of
the small intestine, and consists of a head, a body, and a tail.
Roughly 99% of the exocrine cells of the pancreas are arranged in
clusters called acini.
Pancreatic Islets
20
Each pancreatic islet includes four types of hormone-secreting cells:
1. Alpha or A cells constitute about 17% of pancreatic islet cells and
secrete glucagon.
2. Beta or B cells constitute about 70% of pancreatic islet cells and
secrete insulin.
3. Delta or D cells constitute about 7% of pancreatic islet cells and
secrete somatostatin.
4. F cells constitute the remainder of pancreatic islet cells and secrete
pancreatic polypeptide.
Cell Types in the Pancreatic Islets
21
22
Ovaries and Testes
23
Gonads are the organs that produce gametes—sperm in males and
oocytes in females. In addition to their reproductive function, the
gonads secrete hormones.
The ovaries, paired oval bodies located in the female pelvic cavity,
produce several steroid hormones, including two estrogens and
progesterone.
The male gonads, the testes, are oval glands that lie in the
scrotum.
The main hormone produced and secreted by the testes is
testosterone, an androgen or male sex hormone.
Cont.
24
Pineal Gland and Thymus
The pineal gland (PI-N-ē-al = pinecone shape) is a small endocrine gland
attached to the roof of the third ventricle of the brain at the midline.
The pineal gland secretes melatonin.
25
1-The endocrine glands consist of -------
A. Sebaceous (oil).
B. Pituitary, thyroid.
C. Sweat gland.
D. Mucous.
2- Thyroid gland is located--------
A. Just inferior to the larynx.
B. Just posterior to the larynx.
C. Just superior to the larynx.
D. Just anterior to the larynx.
3- the pancreatic gland is located in ---------
A. The curve of the large intestine.
B. The curve of the duodenum.
C. The curve of the jejunum.
D. The curve of the liver.
4- The ovaries, paired oval bodies located
in the ---------
A. Abdominal cavity.
B. Renal cavity .
C. Male pelvic cavity .
D. Female pelvic cavity .
System ReviewChoose Correct answer?
26