Endocrine system 1. General data on endocrine glands 2. Morphofunctional characteristics of the endocrine glands a) Pituitary gland b) Epiphysis c) Thyroid gland d) Parathyroid glands e) Thymus f) Adrenal glands g) Pancreas h) gonads 3. Organogenesis of the endocrine system Lecturer: PhD, professor Tamara Hacina
90
Embed
Endocrine system - USMF · 2019-03-04 · •The endocrine system acts with nervous system to coordinate the body's activities. •Both systems enable cells to communicate with others
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Endocrine system1. General data on endocrine glands
2. Morphofunctional characteristics
of the endocrine glands
a) Pituitary gland
b) Epiphysis
c) Thyroid gland
d) Parathyroid glands
e) Thymus
f) Adrenal glands
g) Pancreas
h) gonads
3. Organogenesis of the endocrine
system
Lecturer: PhD, professor Tamara
Hacina
Characteristics of the endocrine
system
•The endocrine system functions in the regulation
of body activities.
•It acts through chemical messengers called
hormones that influence growth, development,
metabolic activities.
•Its action is measured in minutes, hours, or weeks
& is more generalized than the action of the
nervous system.
The endocrine system• The endocrine system comprises a group of
ductless glands that secrete chemical messenger substances, called hormones, into the bloodstream.
• Hormones are responsible for the long-term regulation of many bodily functions.
• The endocrine system includes the pituitary, thyroid, parathyroid, thymus and adrenalglands, and the pancreas and gonads (ovaries and testes).
Common features of the endocrine
glands
• Superior blood-supply: fenestrated
capillaries,on at least one side
• Ductless glands
• Cells organized in “chunks”: blocks,
islands, plates, cords
• Epithelial in origin (an or two
exceptions)
• Polihedral cells with round nucleus
• Plentifull organelle content (indicates
synthesis)
• The endocrine system acts with nervous system to
coordinate the body's activities.
• Both systems enable cells to communicate with others by
using chemical messengers.
• The endocrine system uses chemical messengers
called hormones that are transported by the circulatory
system (blood). They act on target cells that may be
anywhere in the body.
• The endocrine system is slower than the nervous system
because hormones must travel through the circulatory
system to reach their target.
• Target cells have receptors that are specific to the
signaling molecules. The binding of hormones to the
Thyroid GlandThe thyroid gland is shaped like a butterfly
and usually weighs less than one ounce.
The thyroid cartilage covers the larynx and
produces the prominence on the neck known
as the "Adam's Apple".
The thyroid gland controls the rate at which
the body produces energy from nutrients.
If the body does not get enough iodine, the
thyroid gland cannot produce a proper
amount of hormones for this conversion
process.
The result can be a goiter, an enlargement of
the thyroid gland.
In some parts of the world, iodine is so
scarce that most of the population have
goiters.
37
• Thyroid is composed of spherical follicles
– Follicle cells: produce thyroglobulin, the precursor of
thryoid hormone (thyroxin)
– Colloid lumen is of thyroglobulin
– Parafollicular “C” cells: produce calcitonin
Action of
thyroid
hormons
Hypersecretion of the
thyroid glands at adults
Exophthalmos of
Grave’s disease
Enlarged thyroid
(goiter) from
iodine deficiency
1. Cretinism (in infancy) – dwarfs, retarded
- hypothyroidism
2. Myxedema (in adults) – swelling, slowness
- hypothyroidism
3. Regular Goiter – too little iodine yields
pituitary response
4. Toxic Goiter – TSH overproduction
Malfunctions of Thyroid gland
Hyposecretion of the
thyroid gland at
adults
Hyposecretion of the thyroid gland in childhood
Hyposecretion of the thyroid gland
Parathyroid Glands• There are four
parathyroid glands, which are located behind the thyroid.
• The sole purpose of the gland is to regulate the calcium level in our bodies within a very narrow range in which our muscular and nervous systems can function properly.
• Regulates or supports a variety of important cardiovascular,
metabolic, immunologic, and homeostatic functions including
water balance
People with adrenal insufficiency: these stresses can cause
hypotension, shock and death: must give glucocorticoids, eg for
surgery or if have infection, etc.
Adrenal medulla
• Part of autonomic nervous system
• Spherical chromaffin cells are modified postganglionic sympathetic neurons
– Secrete epinephrine and norepinephrine
– Amine hormones
– Fight, flight, fright
• Vesicles store the hormones
Pathology of
Adrenal gland
Cushing’s syndrome:
Usually caused by an
ACTH-secreting
pituitary tumor, rarely
by tumor of adrenal
cortex, iatrogenic
Addison’s
disease
Hyposecretion
(under
secretion) of
adrenal cortex
Usually involves
cortisol and
aldosterone: low
blood glucose
and sodium,
severe
dehydration,
fatigue, loss of
appetite,
abdominal pain
Note the
generalised skin
pigmentation but
ispecially the
deposition in the
palmer skin, nails
& gums.
The pancreas
• Endocrine tissue in the pancreas (the islets of Langerhans) secrete hormones that regulate the blood sugar level.
Ilets of
Langerhans
Pancreas
Pancreas • The Pancreas has
two main
functions:
• to produce
pancreatic
endocrine
hormones, which
help regulate
many aspects of
our metabolism,
and
• to produce
pancreatic
digestive enzymes.
Located slightly behind the stomach
• Insulin: reduces blood glucose
– Facilitates glucose transport into the
cells
– Promotes glycogenesis
– Inhibits gluconeogenesis
• Glucagon: increases blood glucose
• When low plasma
glucose levels occur, the
catecholamines are
released to accelerate
lypolysis.
• Triglycerides are
reduced to free fatty
acids by lipase which is
activated by:
– Cortisol
– Epinephrine
– Norepinephrine
– Growth Hormone
• Glucose must not only be
delivered to the cells, it
must also be taken up by
them. That job relies on
insulin.
• Exercise may enhance
insulin’s binding to
receptors on the muscle
fiber.
• Up-regulation (receptors)
occurs with insulin after 4
weeks of exercise to
increase its sensitivity
(diabetic importance).
73
The PancreasExocrine and endocrine
cells
• Acinar cells (forming
most of the pancreas)
– Exocrine function
– Secrete digestive
enzymes
• Islet cells (of
Langerhans)
– Endocrine function
ThymusThe thymus is a gland that forms part of the immune
system.
It is situated in the upper part of the chest, behind the
breastbone, and is made up of two lobes that join in front
of the trachea.
Each lobe is made of lymphoid tissue, consisting of tightly
packed white blood cells and fat.
The thymus enlarges from about the 12th week of
gestation until puberty, when it begins to shrink.
Its function is to transform lymphocytes (white blood cells
developed in the bone marrow) into T-cells (cells developed
in the thymus).
These cells are then transported to various lymph glands,
where they play an important part in fighting infections
and disease.
Swelling of lymph glands and fever are a signal that
immune cells are multiplying to fight off invaders of the
body: bacteria, fungi, viruses or parasites.
Gonads Female ovariesMale testes
Gland Principle hormones Action
Male gonads
The testes
Testosterone Male secondary sexual
characteristics
Female gonads
The ovaries
Oestrogen
(estrogen)
Progesterone
• Female secondary sexual
characteristics
• Development of the
endometrium
• Maintenance of endometrium
Testes
The scrotum is a sac that hangs under the penis and holds the testes.
It is divided internally into two halves by a membrane; each half containing a testis.
It has an outer layer of thin, wrinkled skin over a layer of tissue which contains muscle.
The testicle lies inside the scrotum and produces as many as 12 trillion sperm in a male's
lifetime, about 400 million of which are ejaculated in one average intercourse.
Each sperm takes about seventy-two days to mature and its maturity is overseen by a
complex interaction of hormones.
The scrotum has a built-in thermostat, which keeps the sperm at the correct temperature.
It may be surprising that the
testicles should lie in such a
vulnerable place, outside the body,
but it is too hot inside.
The sperm production needs a
temperature which is three to five
degrees below body temperature.
If it becomes too cool on the
outside, the scrotum will contract
to bring the testes closer the body
for warmth.
Ovaries
The
ovaries
produce a
female
hormone,
called
estrogen,
and store
female sex
cells, or
“ova.”
The Gonads (testes and ovaries) main source of the steroid sex hormones
• Testes– Interstitial cells secrete androgens
– Primary androgen is testosterone
• Maintains secondary sex characteristics
• Helps promote sperm formation
• Ovaries– Androgens secreted by thecal folliculi
• Directly converted to estrogens by follicular granulosa cells
– Granulosa cells also produce progesterone
– Corpus luteum also secretes estrogen and progesterone
Functions of
the gonads
Regulation of the ovarian
and menstrual cycles
• The ovarian cycle (the monthly sequence of changes that take place in the ovaries) is regulated by the pituitary hormones follicle stimulating hormone(FSH) and luteinising hormone (LH).
• The menstrual cycle (the monthly sequence of changes that take place in the uterus) is regulated by the ovarian hormones estrogen and progesterone.
• Both cycles are regulated by complex feedback processes.
Hormonal action on the female reproductive organs
Progesterone Luteinising
hormone (LH)
Estrogen Follicle
stimulating
hormone (FSH)
Ovarian hormone
(corpus luteum)
Target –
endometrium
Role –
maintenance of
endometrium
Predominant in
second part of
cycle
Anterior pituitary
hormone
Target – corpus
luteum
Roles – ovulation,
maintenance
of corpus
luteum
Predominant in
second part of
cycle
Ovarian hormone
(ovarian follicle)
Target –
endometrium
Role – repair of
endometrium after
menstruation
Predominant in
first part of cycle
Anterior pituitary
hormone
Target – ovarian
follicle
Role –
maturation of
ovarian
follicle
Predominant in
first part of
cycle
Hormonal control of ovarian/menstrual cycle
85
Endocrine cells in various organs continued
• The heart: atrial natriuretic peptide (ANP)
– Stimulates kidney to secrete more salt
– Thereby decreases excess blood volume, high BP and high blood sodium concentration
• GI tract & derivatives: Diffuse neuroendocrine system (DNES)
• The placenta secretes steroid and protein hormones
– Estrogens, progesterone
– CRH
– HCG
• The kidneys
– Juxtaglomerular cells secrete renin
• Renin indirectly signals adrenal cortex to secrete aldosterone
– Erythropoietin: signals bone marrow to increase RBC production
• The skin
– Modified cholesterol with uv exposure becomes Vitamin D precursor
– Vitamin D necessary for calcium metabolism: signals intestine to absorb CA++
Pathology• Pituitary
– Gigantism –too much GH in childhood
– Acromegaly – too much GH in adulthood
– Pituitary dwarfs – too little GH in childhood
– Diabetes insipidus - too much ADH
• Pancreas– Diabetes mellitus – one type of insulin (not enough)
• Thyroid– Hyperthyroidism, commonest is Grave’s disease (autoimmune)