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HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2

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Page 1: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

HOMEOSTASIS:THE LIVER AND PANCREAS

CHAPTER 4.2

Page 2: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Overview Mammalian Liver

Anatomy Functions

Lipid Regulation Protein and Amino Acid Regulation Blood Sugar regulation Bile production Other functions

Chemical classification of Hormones Water and lipid soluble hormones Hormonal Feedback loop Antagonistic Hormones

Mammalian Pancreas Blood sugar regulation

Page 3: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Liver: Bodily Metabolic Centre

Largest gland in the body with many metabolic and regulatory roles

Lies on the upper right section of the abdominal cavity, under the diaphragm

Receives plentiful blood supply where substances are extracted for processing. 2 main vessel:- Hepatic artery – brings oxygenated blood from dorsal artery Hepatic portal vein – bring nutrient rich blood from small

intestines Hepatic vein - Blood from liver is brought back to heart

via this vein and posterior vena cava.

Liver cell/hepatocytes are undifferentiated and structurally identical.

Page 4: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 5: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Contains approximately 0.1 millions lobules that serve as structural and functional units Each lobe contains rows of liver cells

1. Liver artery arm2. Bile duct 3. Bile duct arm4. Portal vein a. Lobe (simplified) b. Hepatocyte

Page 6: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 7: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Functions of the Liver Over 500 functions. Most importantly

Regulation of lipids Lipids used for energy for cellular functions (more energy

than glucose) Liver responsible for proper lipid concentrations in the blood. Lipids removed from blood by liver cells or transported to fat

storage areas in the form of adipose tissue or lipoproteins for brain and nerve tissue synthesis

Cholesterols removed and some converted to bile salts Fatty acids conversion to acetyl-coA via fatty acid

spiral/lipolysis Lipid synthesis – cholesterol synthesis (Mevalonate

pathway) and lipogenesis Abnormally high lipids – arthrosclerosis, coronary thrombosis

Page 8: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 9: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 10: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 11: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 12: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Functions of Liver

Regulation of amino acids and proteins Non-essential aa can be synthesised by

transamination

Excess aa and proteins cannot be stored in the body. Any excess in returned to the liver for catabolism through deamination into non-nitrogenous and nitrogenous parts (amino group - NH2)

The non-nitrogenous, keto acid is converted into glucose in the liver to be stored as glycogen or broken down to release heat.

The nitrogenous ammonia, is potently toxic. Hence, it is converted into urea using the urea or ornithine cycle

This is transported by the blood the kidneys for excretion

Page 13: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 14: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 15: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 16: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 17: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

+ ATP

Page 18: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 19: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 20: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Functions of Liver

Bile production Bile comprises of bile salts and bile

pigments that is stored in the gall bladder till needed in fat digestion

Bile salts are synthesized from cholesterol Bile pigments (yellowish-green) are from the

incorporation of the by-products of red blood cell disassembly

Gallstones are an accumulation of cholesterol crystals that can cause blockage of the bile/biliary duct and increase pressure of the gall bladder.

Accumulation stems from bile constituents’ imbalance.

Page 21: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 22: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Functions of Liver

Regulation of blood sugar level Excess glucose is either converted by pancreatic

insulin for storage as glycogen; or broken down into H2O + CO2 + heat

When the body has excess glucose, glycogenesis is the synthesis of glycogen from glucose that is stimulated in the presence of the pancreatic hormone insulin.

Prevention of glucose from falling below the crucial level is performed by a process called glycogenolysis.

Glycogenolysis is the catabolism of glycogen that requires the activation of hepatic enzyme glycogen phosphorylase by pancreatic hormone glucagon.

Page 23: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Hexokinase is stimulated by insulin

Glycogen phosphorylase is stimulated by glucagon

Page 24: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Functions of Liver

Regulation of blood sugar level In skeletal muscles, glycogen cannot be

converted into glucose directly through glucose-6-phosphate route as in the liver due to the lack of the enzyme glucose-6-phosphotase.

Instead it is channeled through glycolysis and converted into pyruvate. Consecutively, processed through aerobiosis or anaerobiosis.

In anaerobiosis, lactate that will be carried to the liver for conversion – firstly, to glucose and then glycogen using the Cori cycle.

Page 25: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Cori Cycle

Page 26: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Functions of Liver

Thermoregulation Liver is large Plenty of blood and high metabolic rate Hence, easy to release excess heat to maintain body

temperature.

Detoxification of blood – Kupffer cells Elimination of steroids Storage of blood Formation of red blood cells in foetus Production of plasma protein (fibrinogen,

albumin and globulin) Storage of vitamins and minerals

Page 27: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Chemical Classes of Hormones

Three major classes of molecules function as hormones in vertebrates: Polypeptides (proteins and peptides) Amines derived from amino acids Steroid hormones

Lipid-soluble hormones (steroid hormones) pass easily through cell membranes, while water-soluble hormones (polypeptides and amines) do not

The solubility of a hormone correlates with the location of receptors inside or on the surface of target cells

Page 28: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Fig. 45-3

Water-soluble Lipid-soluble

Steroid:Cortisol

Polypeptide:Insulin

Amine:Epinephrine

Amine:Thyroxine

0.8 nm

Page 29: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Fig. 45-5-2

Signalreceptor

TARGETCELL

Signal receptor

Transportprotein

Water-solublehormone

Fat-solublehormone

Generegulation

Cytoplasmicresponse

Generegulation

Cytoplasmicresponse

OR

(a) NUCLEUS (b)

Page 30: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Negative feedback and antagonistic hormone pairs

Hormones are assembled into regulatory pathways

Hormones are released from an endocrine cell, travel through the bloodstream, and interact with the receptor or a target cell to cause a physiological response

A negative feedback loop inhibits a response by reducing the initial stimulus

Negative feedback regulates many hormonal pathways involved in homeostasis

Page 31: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Fig. 45-11Pathway Example

Stimulus Low pH induodenum

S cells of duodenumsecrete secretin ( )

Endocrinecell

Bloodvessel

PancreasTargetcells

Response Bicarbonate release

Neg

ati

ve f

eed

back

Page 32: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Insulin and Glucagon: Control of Blood Glucose

Insulin and glucagon are antagonistic hormones that help maintain glucose homeostasis

Glucose that is absorbed from the gut into the hepatic portal vein, increases the blood glucose concentration. This is detected by the pancreas

The pancreas has clusters of endocrine cells called islets of Langerhans with alpha cells that produce glucagon and beta cells that produce insulin

Page 33: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Pancreas: Endo- and Exocrine Functions Lies deep within the abdominal cavity, on the

posterior of the abdominal wall Elongated and somewhat flattened organ with

endo- and exocrine functions. As an exocrine gland, it functions in the

digestive system due to the secretion of pancreatic juice via the ducts to the small intestines.

As an endocrine gland, it function in the secretion of hormones (insulin, glucagon and somatostatin)

This is thanks to the cells on the islet of Langerhans

Page 34: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 35: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood
Page 36: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Fig. 45-12-1

Homeostasis:Blood glucose level

(about 90 mg/100 mL)

Insulin

Beta cells ofpancreasrelease insulininto the blood.

STIMULUS:Blood glucose level

rises.

Page 37: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Fig. 45-12-2

Homeostasis:Blood glucose level

(about 90 mg/100 mL)

Insulin

Beta cells ofpancreasrelease insulininto the blood.

STIMULUS:Blood glucose level

rises.

Liver takesup glucoseand stores itas glycogen.

Blood glucoselevel declines.

Body cellstake up moreglucose.

Page 38: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Fig. 45-12-3

Homeostasis:Blood glucose level

(about 90 mg/100 mL)

Glucagon

STIMULUS:Blood glucose level

falls.

Alpha cells of pancreasrelease glucagon.

Page 39: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Fig. 45-12-4

Homeostasis:Blood glucose level

(about 90 mg/100 mL)

Glucagon

STIMULUS:Blood glucose level

falls.

Alpha cells of pancreasrelease glucagon.

Liver breaksdown glycogenand releasesglucose.

Blood glucoselevel rises.

Page 40: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Fig. 45-12-5

Homeostasis:Blood glucose level

(about 90 mg/100 mL)

Glucagon

STIMULUS:Blood glucose level

falls.

Alpha cells of pancreasrelease glucagon.

Liver breaksdown glycogenand releasesglucose.

Blood glucoselevel rises.

STIMULUS:Blood glucose level

rises.

Beta cells ofpancreasrelease insulininto the blood.

Liver takesup glucoseand stores itas glycogen.

Blood glucoselevel declines.

Body cellstake up moreglucose.

Insulin

Page 41: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Target Tissues for Insulin and Glucagon

Insulin reduces blood glucose levels by Promoting the cellular uptake of glucose Slowing glycogen breakdown in the liver Promoting fat storage (lipogenesis)

Glucagon increases blood glucose levels by Stimulating conversion of glycogen to glucose in the

liver Stimulating breakdown of fat and protein into

glucose

Page 42: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Diabetes Mellitus

Diabetes mellitus is perhaps the best-known endocrine disorder

It is the failure of glucose homeostasis

It is caused by a deficiency of insulin or a decreased response to insulin in target tissues

It is marked by elevated blood glucose levels

Page 43: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

Type I diabetes mellitus (insulin-dependent) (30%) is an autoimmune disorder in which the immune system destroys pancreatic beta cells

Type II diabetes mellitus (non-insulin-dependent) (70%) involves insulin deficiency or reduced response of target cells due to change in insulin receptors

Diabetes Mellitus

Page 44: HOMEOSTASIS: THE LIVER AND PANCREAS CHAPTER 4.2. Overview  Mammalian Liver  Anatomy  Functions Lipid Regulation Protein and Amino Acid Regulation Blood

You should now be able to:

1. Note the anatomy and function of the liver lobules and their components

2. Difference in canaliculi and sinusoid.3. Distinguish between the major functions

of the liver especially lipid, protein, amino acids and glucose regulation.

4. Describe the difference between water-soluble and lipid-soluble hormones

5. Explain how the antagonistic hormones insulin and glucagon regulate carbohydrate metabolism

6. Distinguish between type 1 and type 2 diabetes