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Pancreas.ppt
1. Pancreas.
• Introduction.
• The pancreas is a double gland partly exocrine and
endocrine.Thus it is referred to as a heterocrine gland.
• Location.
• The pancreas lies just behind the lower part of the
stomach.
• Shape and Size.
• It is J-shaped or retort shaped.It is about 6-8 inches
long,1-2 inch broad and ½ inch thick.The pancreas
weight about 80-85 grams.
2. • Parts of Pancreas.
• The pancreas is composed of two major types of tissues.
• 1- The Acini,Secrete digestive juices.
• 2- The islets of Langerhans.
• Human pancreas contains about 1-2 million islets.
• Islets of Langerhans consists of four types of cells.
• Alpha Cells (25%),which secrete glucagon.
• Beta Cells (60%),which secrete insulin.
• Delta Cells (10%),which secrete somatostatin.
• PP-Cells (5%),which secrete pancreatic polypeptide.
3. Insulin.
• Introduction.
• Insulin is a small protein acts to lower the blood
glucose level.This hormone is secreted by beta
cells of the islets of Langerhans of the pancreas.
• Chemistry.
• Insulin is a polypeptide with 51 amino acids and
a molecular weight of 5808.It has two amino
acids chains called Alpha and Beta chains which
are linked by disulfide bridges.The Alpha chain
of insulin contains 21 amino acids,and Beta
chains contains 30 amino acids.
4. • Plasma Level and Half-Life.
• Basal level of insulin in plasma is 10
uU/ml.Its biological half-life is 5 minutes.
• Synthesis.
• Synthesis of insulin occurs in rough
endoplasmic reticulum of beta cells in
islets of Langerhans.It is synthesized as
preproinsulin that gives rise to proinsulin.
5. • Proinsulin undergoes a series of peptic
cleavages leading to the formation of
mature insulin and C peptide.
• C peptide is a connecting peptide that
connects Alpha and Beta chains.
• At the time of secretion,C peptide is
detached.
6. • Metabolism.
• Binding of insulin to insulin receptor is
essential for removal from circulation and
degradation of insulin.Insulin is degraded
in liver and kidney by a cellular enzyme
called insulin protease or insulin degrading
enzyme.
7. • Actions of Insulin.
• Insulin is the important hormone that is
concerned with regulation of carbohydrate
metabolism and blood sugar level.It also
concerned with metabolism of proteins and fats.
• Effects on Carbohydrate metabolism.
• 1- It increases the entry of glucose into cells by
stimulating the process of facilitated
diffusion,especially in muscles,adipose tissue,
8. • The heart,smooth muscles of the uterus by
activating glucokinase.
• But on the other hand,insulin does not facilitate
glucose entry into the brain and RBCs.
• 2- It increases utlization of glucose for energy.
• 3- It increases glycogen storage in cells.
• 4- It increases the conversion of glucose into fat
to be stored in adipose tissues.
9. • 2-Effects on Protein metabolism.
• 1- Facilitates the transport of amino acids into
the cell from blood.
• 2- Increases the premeability of cell membrane
for amino acids.
• 3- It promotes translation of mRNA in ribosomes
to form new proteins.
• 4- It promotes transcription of DNA in the
nucleus to form mRNA.
• 5-It inhibits protein catabolism.
10. • 3- Effects on Fat metabolism.
• 1- Form fatty acids from excess liver glucose by
activating acetyl-s-CoA carboxylase.
• 2- Fatty acids are utilized from triglycerides
which are stored in adipose tissue.
• 3-It inhibits hydrolysis of triglycerides in fat cells
by inhibiting hormone sensitive lipase.
11. • 4-Effects on Growth.
• 1- Along with growth hormone,insulin promotes
growth of body.
• 2- It enhances the transport of amino acids into
the cells and synthesis of proteins in the cells.
• Regulation of Insulin Secretion.
• Insulin secretion mainly regulated by blood
glucose level.
12. • In addition,other factors like,
• Amino Acids.
• Lipid Derivatives.
• Gastrointestinal Hormones.
• Endocrine Hormones.
• Autonomic nerve fibers.
• Role of Blood Glucose Level.
• When the blood glucose level is normal (80-
100mg/dl),the rate of insulin secretion is low (up
to 10uU/minute).
13. • When the blood glucose level increases
between 100-120mg/dl,the rate of insulin
secretion rises rapidly to
100uU/minute.when the blood glucose
level rises above 200mg/dl,the rate of
insulin secretion also rises very rapidly up
to 400uU/minute.
14. • Role of Proteins.
• The excess amino acids in the blood also
stimulates insulin secretion.The potent
amino acids are Arginine and Lysin.
• Role of Lipid Derivatives.
• The Beta ketoacids such as acetoacetate
also increase insulin secretion.
15. • Role of Gastrointestinal Hormones.
• Insulin secretion is increased by some of the
gastrointestinal Hormones such as gastrin,secretin and
cholecystokinin.
• Role of Endocrine Hormones.
• The hormones like glucagon,growth hormone and
cortisol also stimulate insulin secretion indirectly.
• Role of Autonomic Nerve.
• The stimulation of parasympathetic nerve to the
pancreas increases the secretion of insulin.
16. Glucagon.
• Introduction.
• Human glucagon is a hormone whose principle
physiological activity is to increase blood
glucose levels.This hormone is secreted by the
Alpha cells of the islets of Langerhans of the
pancreas.
• Chemistry and Half-Life.
• Glucagon is a polypeptide with a molecular
weight of 3485.
17. • It contains 29 amino acids.Half-Life of glucagon
is 3-6 minutes.
• Synthesis.
• Glucagon is synthesized from the
preprohormone precursor called preproglucagon
in the Alpha cells of islets.
• Metabolism.
• About 30% of glucagon is degraded in liver and
20% in kidney.50% of circulating glucagon is
degraded in blood itself by enzymes such as
serine and cysteine proteases.
18. • Actions of Glucagon.
1- Effects on Carbohydrate metabolism.
1- Increases the blood glucose level
(hyperglycemic hormone)in the following ways.
2- It promotes glycogenolysis in the liver by
activating phosphorylase.
3- It promotes gluconeogenesis.
19. • 2- Effects on Protein Metabolism.
• Glucagon increases transport of amino
acids into liver.
• The amino acids are utilized for
gluconeogenesis.
• 3-Effects on Fat Metabolism.
• 1- It mobilizes fatty acids from adipose
tissues by activating adipose cell lipase.
20. • 2- It inhibits storage of triglycerides in the liver.
• 3- It promotes utilization of free fatty acids for
energy.
• 4- It promotes gluconeogenesis from glycerol.
• 4- Other Actions.
• 1- Inhibits the secretion of gastric juice.
• 2- Increases the secretion of bile from liver.
21. • Regulation of Glucagon Secretion.
• The secretion of glucagon is controlled mainly
by blood glucose and amino acid levels in the
blood.
• The important factor that regulates the secretion
of glucagon is the decrease in blood glucose
level.When blood glucose level decreases below
80mg/dl of blood,Alpha cells of islets of
Langerhans are stimulated and more glucagon
is released.
22. • The glucagon in turn increases the blood
glucose level.On the other hand,when the blood
sugar level increases,Alpha cells are inhibited
and the secretion of glucagon decreases.
• 2- Role of Amino acid Level in Blood.
• Increase in amino acid level in blood stimulates
the secretion of glucagon.Glucagon ,in turn
converts the amino acids into glucose.
23. • 3-Role of Other Factors.
• Factors which increase glucagon
secretion.
• Exercise.
• Stress.
• Gastrin.
• Cortisol.
• Cholecystokinin.
25. Diabetes Mellitus.
• Introduction.
• Diabetes Mellitus is a metabolic disorder
characterized by high blood sugar (glucose)
level associated with other manifestations.In
most of the cases,the diabetes mellitus develops
due to the deficiency of insulin.
• Types of Diabetes Mellitus.
• Type 1 Diabetes Mellitus.
• Type 2 Diabetes Mellitus.
26. • Type 1 Diabetes Mellitus.
• It is due to the deficiency of insulin.
• It occurs b/c of the dysfunction or absence of
Beta cells in islets of Langerhans.
• Also called insulin dependent diabetes mellitus
(IDDM).
• It is not associated with obesity.
• May be associated with acidosis or ketosis.
27. • May occur at any age of life.
• Usually occur before 40 year of age.
• Causes of Type 1 Diabetes Mellitus.
• 1- Degeneration of Beta cells in the islets of
Langerhans of pancreas.
• 2- Destruction of Beta cells by viral infection.
• 3- Destruction of Beta cells during Autoimmune
diseases.
•
28. • Type 2 Diabetes Mellitus.
• It is due to the absence or deficiency of
insulin receptors.
• It usually occurs after 40 years.
• May or may not be associated with
ketosis.
• Also called non insulin dependent diabetes
mellitus (NIDDM).
29. • Causes for Type 2 Diabetes
Mellitus.
• The diabetes develops b/c of absence
reduced number of insulin receptors in the
cells of the body.
• Major causes,
• 1- Hereditary disorders.
• 2- Endocrine disorders.
30. • Signs and symptoms of Diabetes
Mellitus.
• 1- Increased blood sugar level (300-400mg/dl)
due reduced utilization by tissue.
• 2- Mobilization of fats from adipose tissue for
energy purpose,leading to elevated fatty acid
content in blood.
• 3- Depletion of proteins from the tissues.
31. Others Signs and Symptoms of
diabetes mellitus.
• 1- Glucosuria. Loss of glucose in urine.
• 2- Osmotic diuresis. Diuresis due to osmotic effects.
• 3- Polyuria. Excess urine formation.
• 4- Polydipsia. Increase in water intake.
• 5- Polyphagia. Intake of excess food.
• 6- Asthenia. Loss of strength.
• 7- Circulatory Shock. Osmotic diuresis lead to dehydration,which causes
circulatory shock.It occurs only in severe diabetes.
•
Others Signs
32. • Complications of Diabetes Mellitus.
• 1- Cardiovascular complications like,
• Hypertension.
• Myocardial infarction.
• 2- Degenerative changes in retina called
diabetic retinopathy.
• 3- Degenerative changes in kidney known as
diabetic nephropathy.
