The document summarizes key aspects of the endocrine system. It describes how hormones are chemical messengers that influence metabolic activity by binding to receptors and initiating responses. The major endocrine glands - pituitary, thyroid, parathyroid, thymus, pancreas, adrenal glands, testes, and ovaries - are described along with their locations, secretions, and functions in processes like reproduction, growth, metabolism regulation, and stress response. The hypothalamus links the nervous system to the endocrine system by secreting hormones that stimulate or inhibit pituitary secretions.

2. Endocrine System
• The endocrine system influences metabolic activity
by means of hormones (hormone 5 to excite).
Hormones are chemical messengers secreted by
cells into the extracellular fluids. These messengers
travel through the blood and regulate the metabolic
function of other cells in the body.
• Binding of a hormone to cellular receptors initiates
responses that typically occur after a lag period of
seconds or even days. But, once initiated, those
responses tend to last much longer than those
induced by the nervous system.

3. • Hormones ultimately target most cells of the
body, producing widespread and diverse
effects. The major processes that these “mighty
molecules” control and integrate include:
– Reproduction
– Growth and development
– Maintenance of electrolyte, water, and nutrient
balance of the blood
– Regulation of cellular metabolism and energy
balance
– Mobilization of body defenses

4. • Endocrine glands, also called ductless
glands, produce hormones and lack ducts.
They release their hormones into the
surrounding tissue fluid (endo within; crine
to secrete), and they typically have a rich
vascular and lymphatic drainage that
receives their hormones

5. Hormones
The Chemistry of Hormones
• A large variety of hormones are produced, nearly all
of them can be classified chemically as either amino
acid based or steroids and eicosanoids
• Amino acid based: Most hormones are amino acid
based. Molecular size varies widely in this group—
from simple amino acid derivatives to peptides to
proteins
• Steroids: Steroid hormones are synthesized from
cholesterol. This hormones produced by the major
endocrine organs, only gonadal and adrenocortical
hormones are steroids.

6. • Eicosanoids which include leukotrienes and
prostaglandins
– Leukotrienes are signaling chemicals that
mediate inflammation and some allergic
reactions.
– Prostaglandins have multiple targets and
effects, ranging from raising blood pressure and
increasing the expulsive uterine contractions of
birth to enhancing blood clotting, pain, and
inflammation

7. Mechanisms of Hormone Action
• All major hormones circulate to virtually all tissues, but
a hormone influences the activity of only those tissue
cells that have receptors for it. These cells are its target
cells.
• A hormone typically produces one or more of the
following changes:
– Alters plasma membrane permeability or membrane
potential, or both, by opening or closing ion channels
– Stimulates synthesis of enzymes and other proteins within
– the cell
– Activates or deactivates enzymes
– Induces secretory activity
– Stimulates mitosis

8. Control of Hormone Release
• The synthesis and release of most hormones
are regulated by some type of negative
feedback mechanism.
Endocrine Gland Stimuli
• Three types of stimuli trigger endocrine glands
to manufacture and release their hormones:
– Humoral stimuli
– Neural stimuli
– Hormonal stimuli.

10. Interaction of Hormones at Target
Cells
1. Permissiveness is the situation in which
one hormone cannot exert its full effects
without another hormone being present.
– For example, reproductive system hormones
largely regulate the development of the
reproductive system. However, thyroid
hormone is also necessary for normal timely
development of reproductive structures. Lack of
thyroid hormone delays reproductive
development.

11. 2. Synergism occurs when more than one
hormone produces the same effects at the
target cell and their combined effects are
amplified.
– For example, both glucagon and epinephrine
cause the liver to release glucose to the blood.

12. 3. Antagonism occurs when one hormone
opposes the action of another hormone.
For example, insulin, which lowers blood
glucose levels, is antagonized by glucagon,
which raises blood glucose levels.

13. Endocrine Glands
 Pituitary gland
 Thyroid gland
 Parathyroid
 Thymus
 Pancreas
 Adrenal gland
 Testes
 Ovaries

15. The hypothalamus is a portion of the brain that containsa
number of small nuclei with a variety of functions.
One of the most important functions of the hypothalamus
is to link the nervous system to the endocrine system via
the pituitary gland.

16. Functions of hypothalamus
• The hypothalamus is responsible for certain
metabolic processes and other activities of the
autonomic nervous system.
• It synthesizes and secretes certain
neurohormones, often called releasing
hormones or hypothalamic hormones, and
these in turn stimulate or inhibit the secretion
of pituitary hormones.
• The hypothalamus controls body
temperature, hunger, fatigue, sleep, etc.

18. The pituitary gland
• The pituitary gland, or hypophysis, is an
endocrine gland about the size of a pea and
weighing 0.5 gramsin humans.
• It is composed of three lobes: anterior,
intermediate, and posterior

19. Functions of pituitary gland
• Growth
• Blood Pressure
• Some aspects of pregnancy and childbirth including
stimulation of uterine contractions duringchildbirth
• Breast milk production
• Sex organ functions in both males andfemales
• Thyroid gland function
• The conversion of food into energy (metabolism)
• Water and osmolarity regulation in thebody
• Water balance via the control of reabsorption of water by
the kidneys
• Temperatureregulation
• Pain relief

21. The thyroid gland
o The thyroid gland or just thyroid is one of the largest
endocrine glands and consists of two connected
lobes.
o Each lobe is about 5 cm long, 3 cm wide and 2 cm
thick.
o The thyroid gland is a butterfly-shaped organ.
o The thyroid gland is found in the neck, below the
thyroid cartilage (which forms “Adam’s apple”).
o Itsecretes throxine hormone also calledT4
o The thyroid also produces calcitonin, which plays a
role in calcium homeostasis.

22. Functions of thyroid gland
• The thyroid gland controls how quickly the
body uses energy, makes proteins, and
controls how sensitive the body is to other
hormones.
• These hormones regulate the growth and rate of
function of many other systems in the body.
• Thyroid hormones act throughout the body,
influencing metabolism, growth and
development and body temperature.
• During infancy and childhood, adequate thyroid
hormone is crucial for brain development

24. Parathyroid
• There are four parathyroid glands, and they
are each aboutthe size of a grain of rice.
• Though they’re located near each other, the
parathyroid glands are not related to the
thyroid gland.
• Parathyroid hormone (PTH) has a very
powerful influence on the cells of your bones
by causing them to release their calcium into
the bloodstream.

25. Functions of Parathyroid Gland
• Parathyroid hormone regulates the body’s
calcium levels.
• The parathyroid essentially helps the
nervous and muscular systems
function properly.

27. The thymus
• The thymus is a specialized organ of the immune
system.
• The thymus is composed of two identical lobes and is
located anatomically in the anterior superior
mediastinum, in front of the heart and behind the
sternum.
• each lobe of the thymus can be divided into
a central medulla and a peripheral cortex
which is surrounded by an outer capsule.
• The thymus is largest and most active during the
neonatal and pre-adolescent periods.
• The thymus produces and secretesthymosin.

28. Helping the body protect itself against autoimmunity,
which occurs when the immune system turns against
itself.
The thymus plays a vital role in the lymphatic system(your
body’s defence network) and endocrine system.
Protects the body from certain threats, including viruses
and infections.

30. The adrenal glands are two glands that sit on top of your
kidneys that are made up of two distinct parts- Theadrenal
cortex and The adrenal medulla.
They are also known as suprarenalglands.
The adrenal glands are two, triangular-shaped organs that
measure about 1.5inches in height and 3inches in length.

31. • The adrenal cortex and the adrenal medulla
have very different functions. One of the
main distinctions between them is that the
hormones released by the adrenal cortex are
necessary for life; those secreted by the
adrenal medulla are not.

33. The pancreas is unique in that it’s both an endocrine and
exocrine gland. In other words, the pancreas has the dual
function of secreting hormones into blood (endocrine) and
secreting enzymes through ducts (exocrine).
The pancreas is a 6 inch-long flattened gland that lies deep
within the abdomen, between the stomach and the spine.
It is connected to the duodenum, which is part of the small
intestine.
It secretes insulin.

34. The pancreas maintains the body’s blood glucose (sugar)
balance.
Primary hormones of the pancreas include insulin and
glucagon, and both regulate blood glucose.
Diabetes is the most common disorder associated withthe
pancreas.

36. The testes (or testicles) are a pair of sperm-producing
organs that maintain the health of the male reproductive
system.
The testes are twin oval-shaped organs about the size ofa
large grape.
They are located within the scrotum, which is the loose
pouch of skin that hangs outside the body behind the
penis.

37. The testes secrete testosterone, which is necessary for
proper physical development in boys.
In adulthood, testosterone maintains libido, muscle
strength, and bone density.
Disorders of the testes are caused by too little testosterone
production.

39. The ovaries are oval shaped and about the size of alarge
grape.
They are located on opposite ends of the pelvic wall,on
either side of the uterus.
The ovaries are each attached tothe fimbria (tissue that
connects the ovaries to the fallopiantube).
Ovaries produce and release two groups of sex hormones—
progesterone and oestrogen.

40. The ovaries maintain the health of the femalereproductive
system.
Diseases associated with the ovaries include ovariancysts,
ovarian cancer, menstrual cycle disorders, and polycystic
ovarian syndrome.

42. Introduction
• Hypophysis cerebri
• Master of endocrine
orchestra
• But under control of
the hypothalamus
• Suspended from
3rd ventricle

43. Measurements
• Small size
• Reddish - Grey, ovoid body
• Transverse - 12 mm
• Antero-posterior - 8 mm
• Weight- 500 mg

44. Situation
• Hypophyseal fossa
roofed by diaphragma
sellae – meningeal
layer of Dura matter
• Capsule adherent to
dura.
• No CSF around Gland

45. Relations
• Anterior – Anterior intercavernous sinus
• Posterior- Posterior intercavernous sinus
• Superior
a. Diapragma sellae
b. Optic chiasma
c. Tubercinerium
d. Infundibular recess of 3rd ventricle
• Inferior
a. Irregular venous channels Between two Layers Of Dura Mater
b. Hypophyseal fossa
c. Sphenoidal Air sinuses
• On Each Side- Cavernous sinus & Structures passing
through it.

46. Presenting parts
The pituitary has two major parts
a. Anterior Lobe / Adenohypophysis
b. Posterior Lobe / Neurohypophysis
Differ in their Origin, Structure &
Function

47. Anterior Lobe
It is an ectodermal
derivative of the
stomatodeum.
a. Highly cellular.
b. Pars Anterior
(Pars Distalis Or
Glandularis).
c. Pars Intermedia.
d. Pars Tuberalis.

50. Histology
• Clusters of epithelial cells surrounded by
reticular fibers
• Sinusoids & Fenestrated capillaries
• Glandular cells are arranged in irregular
clumps or cords between a network of
capillaries
• Types of cells:-
– Chromophobe cells
– Chromophil (acidophil and basophil ) cells.

51. Chromophobe cells
• 50% of population
• Inactive precursor or
degranulated after
release of their most of
hormonal content
• Electron Microscope
shows few granules
inside.
• Melanotropes cells

52. • Epithelial cells found in the anterior and
intermediate lobes of the pituitary.
• These epithelial cells are responsible for
producing the hormones of the anterior
pituitary and releasing them into the
bloodstream.
• Melanotrophs are another type of
chromophobe which secrete melanocyte
stimulating hormone (MSH)

53. Chromophil cells
• 50 % population
• Contains cytoplasmic granules
• The contents of the secretory vesicles
are responsible for the staining
characteristics of the chromophil cells.
i. Acidophil cells (or acidophils)
ii. Basophil cells (or basophils)

55. Acidophil cells
• 40 % of parenchyma, subtype of acidophils are the
– Somatotrophs
– Mammotrophs
• Somatotrophs produce growth hormone (GH or
somatotropin), which stimulates liver cells to produce
polypeptide growth factors which stimulate growth (e.g.
somatomedin which stimulates epiphyseal cartilage )
– overproduction of this hormone may result in gigantism
or acromegaly
• Mammotrophs or lactotrophs secrete prolactin. Their
number increases significantly in late pregnancy and the
early months of lactation

56. Basophil cells
• 10 % of Parenchyma
• Secrete Trophic hormones
• Thyrotrophs produce thyroid stimulating hormone (TSH or
thyrotropin).
• Gonadotrophs produce follicle stimulating hormone (FSH),
which stimulates the seminiferous epithelium in males in
addition to early follicular growth in females.
Gonadotrophs also produce luteinizing hormone (LH),
which stimulates production of testosterone by Leydig cells
in males in addition to late follicular maturation, oestrogen
secretion and formation of corpus luteum in females.

57. • Corticotrophs (or adrenocorticolipotrophs)
secrete
– Adrenocorticotropic hormone (ACTH or
corticotropin)
– Lipotropin (LPH, no known function in
humans).
• Corticotropes are the most frequent cell type in
the pars intermedia.

58. Posterior Lobe / Neurohypophysis
• Neurohypophysis is a diencephalic down
growth connected with the hypothalamus
– Neural Lobe Or Pars Posterior
– Median Eminence
– Infundibular Stem

60. Histology
• Consists of unmyelinated nerve fibers derived from
neurosecretory cells of the supraoptic &
paraventricular hypothalamic nuclei and pituicytes.
• Oval or round nuclei of the pituicytes are visible
• Hypothalamic nerve fibers typically terminate close
to capillaries
• Herring bodies - Scattered, large, and bluish-violet
(in PAS/Orange G stained sections) masses
represent dilations of these nerve fibers.
• Contain neurosecretory products of the
hypothalamic cells.

61. • The neurohormones stored in the main part of the neurohypophysis
are
– Vasopressin (antidiuretic hormone; ADH), which controls reabsorption of
water by renal tubules.
– Oxytocin:- paraventricular nucleus of hypothalamus which
promotes the contraction of uterine smooth muscle in childbirth and the
ejection of milk from the breast during lactation.
• Storage granules containing active hormone polypeptides bound to a
transport glycoprotein, neurophysin, pass down axons from their site
of synthesis in the neuronal somata. The granules are seen as swellings
along the axons and at their terminals, which can reach the size of
erythrocytes

63. Hypothalamic control
• Hypophysiotropic area of hypothalamus
• Hypothalamic paraventricular nuclii and
hypothalamic neurons are helps to regulate
the functions of pituitary gland.

65. Anterior pituitary
• Adrenocorticotrophic hormone (ACTH)
• Thyroid-stimulating hormone (TSH)
• Luteinising hormone (LH)
• Follicle-stimulating hormone (FSH)
• Prolactin (PRL)
• Growth hormone (GH)
• Melanocyte-stimulating hormone (MSH)
Posterior pituitary
• Anti-diuretic hormone (ADH)
• Oxytocin

66. • TRH - Secreted by dorsomedial nucleus
• LHRH – (Luteinizing hormone releasing hormone)
Preoptic area & anterior hypothalamus
• CRH – Corticotropin Releasing hormone - Supra-optic &
paraventricular nucli
• GHRH – Growth hormone releasing hormone - Ventero-
medial nucleus
• GIH - (Growth Inhibiting Hormone) - periventricular
nucleus
• PRH – (Prolactin Releasing Hormone) - Location is not
yet known
• PIH - (Prolactin Inhibiting Hormone) Arcuate nucleus,
dopaminargic. Dopamine inhibits Prolactin release

67. • Dwarfism is a condition in which the growth of
the individual is very slow or delayed, resulting in
less than normal adult stature.
Clinical features:
• Puberty delayed, An average-size trunk
• Short arms and legs, with particularly short upper
arms and upper legs
• Short fingers, often with a wide separation
between the middle and ring fingers
• Limited mobility at the elbows
• A disproportionately large head, with a prominent
forehead and a flattened bridge of the nose
• Progressive development of bowed legs
• Progressive development of swayed lower back
• An adult height around 4 feet
• Sexually active.
Applied anatomy/Applied physiology
Dwarfism

68. Gigantism
Gigantism is a condition characterized by
excessive growth and height significantly
above average. In humans, this condition is
caused by over-production
of growthhormone in childhood resulting in
people between 7 feet (2.13 m) and 9 feet
(2.75 m) in height.
• It occurs before the epiphyseal closure.
CLINICAL FEATURES:
 Very large hands and feet
 Thick toes and fingers
 A prominent jaw and forehead
 Coarse facial features
 Children with gigantism may also have flat
noses and large heads, lips, or tongues.

69. Acromegaly
• Acromegaly is a condition that
results from excess growth
hormone (GH) after the growth
plates have closed.
• The initial symptom is typically
enlargement of the hands and feet.
There may also be enlargement of the
forehead, jaw, and nose. Other
symptoms may include joint pain,
thicker skin, deepening of the
voice, headaches, and problems with
vision. Complications of the disease
may include
• Type 2 diabetes, sleep apnea,
and high blood pressure

71. • The pineal gland, also known as the pineal
body, conarium or epiphysis cerebri, is a
small endocrine gland in the vertebrate brain.
• The shape of the gland resembles a pine cone,
hence its name.
• The pineal gland is located in the epithalamus,
near the center of the brain, between the
two hemispheres, tucked in a groove where the
two halves of the thalamus join.

72. • The epiphysis cerebri is a reddish-grey,
approximately 5 – 8 mm long, pine cone-like
structure that is located in the diencephalic
part of the prosencephalon (forebrain). The
gland was formed as an outward growth of
the roof of the third ventricle.

73. Position
• It’s attachment to either half of the
brain is by the Habenular
commissure and trigone superiorly,
and the posterior commissure
inferiorly.
• The Habenular and posterior
commissures are a part of the pineal
stalk.
• The Habenular commissure is a part
of the superior lamina of the stalk,
while the posterior commissure is a
part of the inferior lamina.
• The space between the laminae is
known as the pineal recess.
• It communicates anteriorly with the
hypothalamic sulcus and the third
ventricle.

74. Relations
Coronal section of the brain
• Superiorly, the splenium of the
corpus callosum
• Superolaterally, the choroid
plexus of the third ventricle
• Inferiorly, the superior and
inferior colliculi
The sagittal section
• Inferiorly the quadrigeminal
plate.
• Anterosuperior the Habenular
commissure and the thalamus.
• The posterior commissure, the
cerebral peduncle

75. • The pineal gland produces melatonin,
a serotonin derived hormone which
modulates sleep patterns in
both circadian and seasonal cycles.

76. Histology
• Pinealocytes:- They
produce and
secrete melatonin.
• Interstitial cells:- they
are located between the
pinealocytes. They have
elongated nuclei and a
cytoplasm.
• Perivascular
phagocytes:- The
perivascular phagocytes
are antigen presenting
cells.

77. Blood Supply
• Supplied from the choroidal branches of
the posterior cerebral artery

78. Nerve supply
• The pineal gland receives
a sympathetic innervation from the superior
cervical ganglion.
• A parasympathetic innervation from
the pterygopalatine and otic ganglia.
• Neurons in the trigeminal
ganglion innervate the gland with nerve
fibers containing the pituitary adenylate
cyclase-activating polypeptide (PACAP.)

79. Applied Anatomy and Physiology
• Pineal gland calcification
• Tumors

81. • The thyroid gland is an endocrine gland in
the neck, consisting of two lobes connected by
an isthmus. It is found at the front of the neck,
below the Adam's apple.
• The thyroid gland secretes thyroid hormones,
which primarily influence the metabolic
rate and protein synthesis.
• The thyroid hormones
– Triiodothyronine (T3)
– Thyroxine (T4)
– Calcitonin,

83. • Effects of thyroid
hormones T3 and T4
– Metabolic,
– Cardiovascular
– Developmental
• Hormonal output from the
thyroid is regulated
by thyroid-stimulating
hormone (TSH) secreted
from the anterior
pituitary gland, which itself
is regulated by thyrotropin-
releasing hormone (TRH)
produced by
the hypothalamus

84. • There are three primary features of the
thyroid
– Follicles
– Follicular cells
– Parafollicular cells

85. Follicles
• Thyroid follicles are small spherical
groupings of cells 0.02–0.9mm in diameter.
It surrounds a core of colloid that consists
mostly of thyroid hormone precursor
proteins called thyroglobulin,
an iodinated glycoprotein.

86. Follicular cells
• The core of a follicle is surrounded by a single
layer of follicular cells. When stimulated by
thyroid stimulating hormone (TSH), these
secrete the thyroid hormones T3 and T4. They
do this by transporting and metabolising the
thyroglobulin contained in the
colloid. Follicular cells vary in shape from flat
to cuboid to columnar, depending on how
active they are.

87. Parafollicular cells
• Scattered among follicular cells and in
spaces between the spherical follicles are
another type of thyroid cell, parafollicular
cells. These cells secrete calcitonin and so
are also called C cells.

88.  The thyroid gland weighs 10 to
20 grams in normal adults.
 Thyroid volume measured by
ultrasonography is slightly
greater in men than women
 it increases with age and body
weight.
 it decreases with increasing
iodine intake.
 The thyroid is one of the most
vascular organs in the body.
Thus, US measurements of
thyroid volume and even nodule
size can differ markedly from
the size after devascularization
and resection.

89. Its location & relations
• The normal thyroid gland is
immediately caudal to the
larynx and encircles the
anterolateral portion of the
trachea.
• The thyroid is bordered by the
trachea and esophagus medially
and the carotid sheath laterally.
• The sternocleidomastoid
muscle and the three strap
muscles (sternohyoid,
sternothyroid, and the superior
belly of the omohyoid) border
the thyroid gland anteriorly and
laterally

90. Shape
• It consists of two lobes connected
by a narrow isthmus.
• Each lobe is pyramidal in shape,
with its apex directed upward and
its base directed downward.
• The isthmus is the narrow part of
the gland connecting the two lobes.
• A small pyramidal lobe projecting
upward from the isthmus is often
present to the left of the midline.

91. BLOOD SUPPLY
The arterial blood supply to
the thyroid gland is primarily
from the right and left
superior and inferior thyroid
arteries, derived from the
external carotid arteries and
thyrocervical trunk,
respectively.
The venous drainage consists
of the superior, middle, and
inferior thyroid veins that
drain into the internal
jugular vein and innominate
vein

92.  Superior thyroid artery:- is the first branch off
the external carotid artery. It extends inferiorly to
the superior pole of the thyroid lobe.
 In addition to supplying the thyroid, the superior
thyroid artery is the primary blood supply to
approximately 15 percent of superior parathyroid
glands.
 The superior thyroid artery is a landmark for
identification of the superior laryngeal nerve, which
courses with the artery until approximately 1 cm
from the superior thyroid pole

93.  Inferior thyroid artery:- is a branch of
the thyrocervical trunk which arises from the
subclavian artery.
 The inferior thyroid artery courses posterior to
the carotid artery to enter the lateral thyroid.
The point of entry can extend from superior to
inferior thyroid poles.
 The inferior thyroid artery also supplies the
inferior parathyroid glands and approximately
85 percent of superior parathyroid glands.

94.  Thyroidea ima artery:- is found in
approximately 3 percent of individuals and
arises from the aortic arch or innominate
artery and courses to the inferior portion of the
isthmus or inferior thyroid poles.
 Surgical control of the thyroid ima artery is
essential during thyroidectomy.
 The thyroidea ima artery can be quite enlarged
in patients with thyroid disease such as goiter
or hyperthyroidism

95. Venous drainage
Superior thyroid
vein:
 It arises from the upper part of
the lobe.
 It ends into the internal jugular
vein.
Middle thyroid vein:
 It arises from the middle of the
lobe.
 It ends into the internal jugular
vein.
Inferior thyroid
veins:
 Arise from the isthmus and
lower parts of the lobes.
 Descend in front of the trachea.
 End into the left brachiocephalic
vein.

96. Lymphatic drainage
The lymphatic vessels of
the thyroid gland drain
into:-
– Pretracheal lymph
nodes.
– Paratracheal lymph
nodes.
The efferent of these
nodes drain into:-
– The deep cervical
lymph nodes.

97. Thyroid Physiology
Synthesis of the thyroid hormone
• Trapping of inorganic iodide from the blood
• Oxidation of iodide to iodine.
• Binding of iodine with tyrosine to form
iodotyrosines.
• Coupling of mono-iodotyrosines and di-
iodotyrosine to form T3, T4

99. • The metabolic effects of the thyroid
hormones are due to unbound T4 and T3.
• T3 is the more important and is also
produced in the periphery by conversion
from T4.
• T3 is quick acting (within a few hours)
whereasT4 acts more slowly (4-14 days)

100. Regulation of thyroid
hormone production

101. • Thyrotropin-releasing hormone (TRH) increases the
secretion of thyrotropin (TSH), which stimulates the
synthesis and secretion of trioiodothyronine (T3) and
thyroxine (T4) by the thyroid gland.
• T3 and T4 inhibit the secretion of TSH, both directly and
indirectly by suppressing the release of TRH.
• T4 is converted to T3 in the liver and many other tissues
by the action of T4 monodeiodinases.
• Some T4 and T3 is conjugated with glucuronide and sulfate
in the liver, excreted in the bile, and partially hydrolyzed in
the intestine.
• Some T4 and T3 formed in the intestine may be
reabsorbed.
• Drug interactions may occur at any of these sites.

102. Effects of Thyroid Hormone
 Fetal brain and skeletal maturation
 Increase in basal metabolic rate
 Increases sensitivity to catecholamines
 Stimulates gut motility
 Increase bone turnover
 Increase in serum glucose, decrease in serum
cholesterol

103. Applied anatomy/Applied physiology
• Hypothyroidism:- A condition in which the
thyroid gland doesn't produce enough thyroid
hormone.
• Hyperthyroidism:- The overproduction of a
hormone by the butterfly-shaped gland in the
neck (thyroid).
• Thyroiditis:- Inflammation of the thyroid, the
butterfly-shaped gland in the neck.
• Thyroid cancer:- A cancer of the thyroid, the
butterfly-shaped gland at the base of the neck.

104. • Goiter:- Abnormal
enlargement of the
butterfly-shaped gland
below the Adam's apple
(thyroid).
• Cretinism is a condition of
severely stunted physical
and mental growth owing
to untreated congenital
deficiency of thyroid
hormone (congenital
hypothyroidism) usually
owing to maternal
hypothyroidism.

106. • The parathyroid
glands are four tiny glands,
located in the neck, that
control the body's calcium
levels.
• Each gland is about the
size of a grain of rice and
weighs approximately 30
milligrams and is 3-4
millimeters in diameter.
• The parathyroids produce
a hormone
called parathyroid hormon
e (PTH).

107. Size and location
 Normal parathyroid glands are
approximately the size of a grain of rice or a
lentil.
 Normal glands are usually about 5 by 4 by 2
millimeters in size and weigh 35 to 50
milligrams.
 Enlarged parathyroid glands can be 50
milligrams to 20 grams in weight, most
typically weighing about 1 gram and 1
centimeter in size

108. • Two unique types of cells are present in the
parathyroid gland:-
• Chief cells, which synthesize and release
parathyroid hormone. These cells are small,
and appear dark when loaded with parathyroid
hormone, and clear when the hormone has
been secreted, or in their resting state.
• Oxyphil cells, which are lighter in appearance
and increase in number with age, have an
unknown function.

109. Functions of Parathormone
• Parathyroid hormone regulates serum
calcium through its effects on bone, kidney, and the
intestine
• PTH reduces the reabsorption of phosphate from
the proximal tubule of the kidney
• PTH increases the activity of 1-α-
hydroxylase enzyme, which converts 25-
hydroxycholecalciferol, the major circulating form of
inactive vitamin D, into 1,25-
dihydroxycholecalciferol, the active form of vitamin
D, in the kidney.

110. Superior parathyroid glands
 Normal superior parathyroid glands are
usually located on the posterior-lateral
surface of the middle to superior thyroid
lobe.
 They lie under the thyroid superficial fascia,
posterior to the recurrent laryngeal nerve
and can be visualized by carefully dissecting
the thyroid capsule in this region.

111. Stimulators
• Decreased serum [Ca2+].
• Mild decreases in serum [Mg2+].
• An increase in serum phosphate
Inhibitors
• Increased serum [Ca2+].
• Severe decreases in serum [Mg2+]
• Calcitriol

113. Blood Supply
• The superior
parathyroid glands
receive most of their
blood supply from the
inferior thyroid artery
and also are supplied
by branches of the
superior thyroid
artery in 15 to 20
percent of patients.

114. Inferior parathyroid glands
 The two inferior parathyroid glands reside
in the anterior mediastinal compartment,
anterior to the recurrent laryngeal nerve.
 They are most often found in the
thyrothymic tract, or just inside the thyroid
capsule on the inferior portion of the
thyroid lobes

115. Blood Supply
• The inferior parathyroid glands receive
their end-arterial blood supply from the
inferior thyroid artery.

116. venous blood is drained via:
1. Superior thyroid veins,
emerges from the apex of
each lateral lobe, draining
in the internal jugular vein.
2. Middle thyroid viens,
emerges from the lower
part of each lat. Lobe.
3. Inferior thyroid veins,
emerges from the isthmus
& lower part of the lat.
Lobe. draining via the
plexus thyreoidea impar in
the left brachiocephalic
vein.

117. Applied anatomy an physiology
• Removal of all the parathyroid glands would
cause decreased serum calcium levels
(hypocalcaemia), in turn leading to tetany
(severe muscle twitches and cramps).

119. • The thymus gland, despite containing glandular
tissue and producing several hormones.
• The thymus is a specialized
primary lymphoid organ of the immune
system.
• Within the thymus, T cells or
T lymphocytes mature. T cells are critical to
the adaptive immune system, where the body
adapts specifically to foreign invaders.

120. • The thymus is largest and most active
during the neonatal and pre-adolescent
periods. By the early teens, the thymus
begins to atrophy and thymic stroma is
mostly replaced by adipose (fat) tissue.
• Thymosin is the hormone of the Thymus.
• Thymosin stimulates the development of T
cells.

121. • Located anatomically
in the anterior
superior mediastinum,
in front of
the heart and behind
the sternum.

122. • The thymus is composed of
two identical lobes.
• The lobes can be divided into
a central medulla and a
peripheral cortex which is
surrounded by an outer
capsule.
• The cortex and medulla play
different roles in the
development of T-cells.
• Cells in the thymus can be
divided into thymic stromal
cells and cells
of hematopoietic origin

123. Cell of thymus
• Stromal cells
include epithelial
reticular cells of the
thymic cortex and
medulla, and dendritic
cells.
• Hassall's corpuscles are
structures found in the
medulla of the
human thymus, formed
from eosinophilic type
VI epithelial reticular
cells arranged
concentrically.

124. Epithelial reticular cells
• There are six different types: Types 1-3 are
in the cortex, and types 4-6 are in the
medulla.
• Epithelial reticular cells are the primary cell
involved with making sure that no T
cells are allowed to survive that will attack
the body's own cells.

125. Thymic dendritic cells
• A minor cell population in lymphoid tissues,
are specialized for presentation of antigenic
peptides to T lymphocytes. Thymic dendritic
cells are involved in the deletion of self-
reactive T lymphocytes.

126. T cells
• A T cell, or T lymphocyte, is a type of
lymphocyte a subtype of white blood cell
that plays a central role in cell-mediated
immunity.

127. T - cell maturation

128. Cortex
• The cortical portion is mainly composed
of lymphocytes, supported by a network of
finely-branched epithelial reticular cells, which
is continuous with a similar network in the
medullary portion. This network forms
an adventitia to the blood vessels.
• The cortex is the location of the earliest events
in thymocyte development, where T-cell
receptor gene rearrangement and positive
selection takes place.

129. Medulla
• The network of reticular cells is coarser
than in the cortex, the lymphoid cells are
relatively fewer in number, and there are
concentric, nest-like bodies called Hassall's
corpuscles. These concentric corpuscles are
composed of a central mass, consisting of
one or more granular cells, and of a capsule
formed of epithelial cells.

130. Blood supply
• The arteries supplying the thymus are
derived from the internal thoracic artery,
and from the superior thyroid
artery and inferior thyroids.

131. Venous Drainage
• The veins end in the left brachiocephalic
vein (innominate vein), and in the thyroid
veins.

132. Nerve Supply
• The nerves are exceedingly minute; they are
derived from the vagi and sympathetic
nervous system. Branches from
the descendens
hypoglossi and phrenic reach the investing
capsule, but do not penetrate into the
substance of the organ.

133. Autoimmune disease
• Autoimmune diseases are caused by a
hyperactive immune system that instead of
attacking pathogens reacts against the host
organism (self) causing disease.
Myasthenia gravis
• Myasthenia gravis is an autoimmune
disease caused by antibodies that
block acetylcholine (Neurotransmitter)
receptors. Myasthenia gravis is often
associated with thymic hypertrophy.

134. Thymomas
• Tumours originating from the thymic
epithelial cells are called thymomas
Thymic Lymphomas
• Tumours originating from the thymocytes
are called thymic lymphomas.

136. • The pancreas is a
glandular organ in the
upper abdomen and
have both exocrine and
endocrine functions
• Endocrine – secrete
hormones insulin and
glucagon
• Exocrine –pancreatic
juice

137. Cells of pancreas
• The pancreas contains
four kinds of cells in
the pancreatic islets
(islets of Langerhans)
1. Alpha cells
2. Beta cells
3. Gamma cells or PP cells
or F cells
4. Delta cells
5. Epsilon Cells
Acinar cell:- this are the
functional unit of the
exocrine pancreas.

138. Alpha cells
• They make up to 20% of the human islet cells
synthesizing and secreting
the peptide hormone glucagon, which elevates
the glucose levels in the blood.
• The pancreas releases glucagon when the
concentration of glucose in the bloodstream falls
too low. Glucagon causes the liver to convert
stored glycogen into glucose, which is released
into the bloodstream

139. Beta cells
• Beta cells (β cells) are a type of cell found in
the pancreatic islets of the pancreas. They
make up 65 – 80% of the cells in the islets.
• The primary function of a beta cell is to
store and release insulin.
– Insulin is a hormone that brings about effects
which reduce blood glucose concentration.
– It regulates the metabolism of carbohydrates
fats and protein.

140. Gamma cells
• PP cells, or gamma cells, are cells which
produce pancreatic polypeptides in
the pancreatic islets (Islets of Langerhans)
of the pancreas.
• They are very few in number and are
polygonal in shape and have very few
organelles and few granules.

141. Delta cells
• Delta cells (δ-cells or D cells) are
somatostatin – producing cells. They can be
found in the stomach, intestine and the
pancreatic islets.
• Somatostatin, also known as growth
hormone–inhibiting hormone (GHIH)
• Somatostatin inhibits insulin and glucagon
secretion.

142. Epsilon cells
Epsilon cells (ε-cells) are endocrine cells
found in the Islets of Langerhans and produce
the hormone ghrelin.
• Ghrelin the "hunger hormone", is a peptide
hormone which functions as
a neuropeptide in the central nervous
system. Besides regulating appetite, ghrelin
also plays a significant role in regulating
the distribution and rate of use of energy

143. Location…
• Epigastric & left
hypochondriac
regions
• Behind the stomach
and lesser sac
• Transversely across
the posterior
abdominal wall at
the level of the L2 &
L3

144. Size and shape
• J shaped or
retort shaped.
• Length-15-20
cm
• Thickness -1.2-
1.8 cm
• Breadth-2.5 -3.8
cm
• Wt-90 gm

145. Regions of pancreas

146. Head
• Enlarged part C shaped, lying within the
concavity of duodenum, consist of
• 3 borders-superior, inferior & right lateral
• 2 surfaces-anterior & posterior
• Uncinate process

147. Head
• Superior border-
– 1st part of duodenum
– Sup. pancreaticodudenal
A.
• Inferior border-
– 3rd part of duodenum
– Inf. pancreaticodudenal
A.
• Rt. lateral border-
– 2nd part of duodenum
– Terminal part of bile duct
– Anastomosis between 2
arteries.

148. Head
Anterior surface
• 1st part of
duodenum.
• Transverse colon
• Jejunum separated
by peritotneum.
• Stomach
• Lesser omentum
• Lesser sac
Posterior surface:
• IVC
• Right Renal veins
• Right crus of
diaphragm
• Bile duct

149. Uncinate process
Triangular projection
which arises from
lower and left part off
the body.
Relations:
• Anterior:
-Superior mesenteric
vessels.
• Posterior
-Aorta
• Above
-Left renal vein

150. Neck
Relations:
Anterior surface
• Peritoneum covering
lesser sac
• Pylorus
Posterior surface
is related to
• superior mesenteric
vein
• portal vein

151. Body
• Elongated part.
• Extends from neck
to the tail.
• Passes toward the
left with slight
upward and
backward inclination

152. Triangular in cross
section
• 3 borders
– Anterior
– Superior
– Inferior
• Tuber omentale -
small projection on
superior border little
to the left of the neck

153. Body-Relations
Borders:
• Anterior attach to
root of the tranverse
mesocolon .
• Superior related to
coeliac trunk, hepatic
artery & splenic
artery
• Inferior is related to
superior mesenteric
artery.

154. Surfaces:
• Anterior is convex
covered by the
peritoneum related
to the lesser sac &
stomach.
• Inferior surface
covered by the
peritoneum related
the DJ flexure coils of
jejunum & Lt. colic
flexure.
Posterior surface
• Aorta
• Left crus of the
diaphragm
• Left kidney
• Left Suprarenal gland
• Left renal vessels
• Splenic vein

155. Tail
• Left end of the
pancreas
• Lies in the
lienorenal ligament,
together with the
splenic vessels
• Related to the lower
part of the spleen

156. Pancreatic juice
• Pancreatic juice is a liquid secreted by
the pancreas, which contains a variety
of enzymes, including
– Trypsinogen
– Chymotrypsinogen
– Elastase
– Carboxypeptidase
– Pancreatic lipase
– Nucleases and amylase

157. Ducts system
• Exocrine part
of pancreas is
drained by the
2 ducts
– Main
– Accessory.

158. Main pancreatic duct of wirsung
• Lies near posterior
surface, 3 mm in diam.
white in colour
• Begins at the tail, runs
throughout the body,
bends at the neck to
run downwards
backwards in the head.
• Herring bone pattern

159. Main pancreatic duct of wirsung…
• In the head of the
pancreas, it is related
to the bile duct(on rt.
side)
• Two ducts open in the
wall of the 2nd part of
the duodenum and
join to form
hepatopancreatic
ampulla of vater which
open as major
duodenal papilla, 8-10
cm distal to pylorus.

160. Accessory duct of Santorini…
• Begins in the lower
part of head, crosses
the main duct with
which it
communicates
• Opens as minor
duodenal papilla in
the 2nd part of
duodenum (6 – 8 cm
distal to pylorus)

161. Arterial supply
• Splenic A.
• Superior pancreatico-
duodenal artery (from
coeliac trunk)
• Inferior pancreatico-
duodenal A.(from
superior mesenteric A)

162. Venous drainage
• Splenic vein
• Superior
mesenteric vein
• Portal vein

163. Nerve supply
• Parasympathetic by
the vagus nerve
controlling secretion.
• Sympathetic from
coeliac & superior
mesenteric plexus.
• Secretion is also
controlled by
hormone secretin-
pancreozymine.

164. Lymphatic drainage
• Head & neck –ventral & dorsal
pancreaticodudenal group LN.
• Body &tail by pancreatico-splenic LN.
• Efferents to Coeliac & sup. mesenteric LN

165. Applied anatomy…
• Congenital
• Truama
• Infection /inflammation
• Tumour
• Procedures

166. Congenital
• Annular pancreas:
Developmental anomaly where ring
of pancreatic tissue surrounds and
obstruct duodenum

167. Truama
• Results from sudden
forceful compression
of abdomen such as
steering wheel leading
to rupture.
• Digestion of pancreas
and surrounding tissue
by free pancreatic
juice is very painful
clinical condition.

168. Inflammation…
Pancreatitis
• May be primary or
secondary due to gall
stone.
• Results in collection of
fluid in the lesser sac
• Pain is poorly localised
,referred to epigastrium.
• Acute pancreatitis is
serious clinical condition
may be due to mumps

169. Carcinoma
• Common in head
• Causes obstructive
jaundice due to BD
compression
• Causes ascites due
to portal vein
compression.
• Causes pyloric
obstruction.

170. Procedures
• Endoscopic retrograde cholangiopancreatico
graphy:- Standard procedure for Dx of pancreatic &
biliary diseases

171. Diabetes mallitus
• Condition in which the pancreas no longer
produces enough insulin or cells stop
responding to the insulin that is produced,
so that glucose in the blood cannot be
absorbed into the cells of the body.
• Symptoms: frequent urination, lethargy,
excessive thirst, and hunger.
• Treatment includes changes in diet, oral
medications, and in some cases, daily
injections of insulin.

173. • The adrenal or suprarenal
glands are
paired retroperitoneal (lyi
ng posterior to the
peritoneum) endocrine
glands situated over the
medial aspects of the
upper poles of
each kidney.
• They
secrete steroid and catech
olamine
hormones directly into the
blood.

174. Position
• The adrenal glands lie in the posterior abdomen,
situated between the superomedial kidney and the
diaphragm. They cover part of the anterior surface
of each kidney.
• The right gland is pyramidal in shape, contrasting
with the semi-lunar shape of the left gland.
• Perinephric (or renal) fascia encloses the adrenal
glands and the kidneys. This fascia attaches the
glands to the crura of the diaphragm. They are
separated from the kidneys by the perirenal fat.

175. • The adrenal glands consist of an outer connective
tissue capsule, a cortex and a medulla.
• Veins and lymphatics leave each gland via the hilum,
but arteries and nerves enter the glands at
numerous sites.
• The outer cortex and inner medulla are the
functional portions of the gland. They are actually
two separate endocrine glands, with different
embryological origins:
– Cortex – derived from the embryonic mesoderm.
– Medulla – derived from the ectodermal neural crest
cells.

176. Cortex
• The cortex is yellowish in colour. It
secretes two cholesterol derived
hormones – corticosteroids and
androgens. Functionally, the cortex can
be divided into three regions which are
(from superficial to deep):
– Zona glomerulosa – produces and
secretes mineralocorticoids such as
aldosterone.
– Zona fasciculata – produces and secretes
corticosteroids such as cortisol. It also
secretes a small amount of androgens.
– Zona reticularis – It
produces androgens,
mainly dehydroepiandrosterone (DHEA),
DHEA sulfate (DHEA-S),
and androstenedione the precursor
to testosterone.

177. • Mineralocorticoids such as aldosterone
regulate salt ("mineral") balance and blood
volume.
• Glucocorticoids such as cortisol influence
metabolism rates of proteins, fats and
sugars ("glucose")

179. Medulla
• The medulla lies in the
centre of the gland, and is
dark brown in colour. It
contains chromaffin cells,
which secrete
catecholamines (such as
adrenaline) into the
bloodstream in response
to stress.
• These hormones produce
a ‘flight-or-fight‘ response.
• Chromaffin cells also
secrete enkephalins which
function in pain control.

182. Anatomical Relations
• The adrenal glands sit in close proximity to
many other structures in the abdomen,
these are important to be aware of clinically.
Right Adrenal Gland
Anterior Posterior
Inferior Venacava Right crus of diaphragm
Right left lobe of liver
Left Adrenal Gland
Anterior Posterior
Stomach Left crus of diaphragm
Pancreas
Spleen

183. Blood Supply
• The adrenal glands have
a rich blood supply,
which is supplied via
three arteries:
• Superior adrenal
artery – arises from the
inferior phrenic artery
• Middle adrenal
artery – arises from the
abdominal aorta.
• Inferior adrenal
artery – arises from the
renal arteries.

184. Venous Drainage
• The right suprarenal
vein drains into
the inferior vena cava
• The left suprarenal
vein drains into the
left renal vein or the
left inferior phrenic
vein.

185. Lymphatics
• Lymph drainage is to
the lumbar lymph
nodes by
adrenal lymphatic
vessels. These vessels
originate from two
lymphatic plexuses –
one deep to the
capsule, and the other
in the medulla.

186. Neural innervation
• The adrenal glands are
innervated by
the coeliac
plexus and abdominopel
vic splanchnic
nerves. Sympathetic
innervation to the
adrenal medulla is via
myelinated pre-synaptic
fibres, mainly from the
T10 to L1 spinal cord
segments.

187. Cushing’s Syndrome
• Cushing’s syndrome
describes the signs and
symptoms associated with
chronically elevated
glucocorticoid levels in
the blood. These include:
• Moon shaped face and
buffalo hump
• Thin skin and easy
bruising
• Hyperglycaemia
• Hypertension

188. Addison’s Disease
• Addison’s disease is
characterised by low
glucocorticoid and
mineralocorticoid levels,
typically due to the
autoimmune destruction of
the adrenal cortex. Stress
may exacerbate the
condition, producing an
Addisonian crisis which must
be treated urgently with IV
cortisol and administration
of dextrose in normal saline
as fluid replacement, in order
to prevent death.

189. Organs Other Than Endocrine