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Anat and Phys > Gastrointestinal Tract III (IV) > Flashcards

Gastrointestinal Tract III (IV) Flashcards

1
Q

Accessory organs of the small intestine with a function in digestion

A

liver: production
gall bladder: storage of bile
pancreas: enzyme and bicarbonate secretion

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2
Q

The liver

A
  • largest gland in body
  • has thin capsule of dense connective tissue
  • weighs 1200g - 1600g
  • high metabolic activity
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3
Q

gross anatomy of the human liver

A
  • consists of four primary lobes: right, left, caudate, quadrate
  • falciform ligament: separated larger right and smaller left lobes, suspends liver from diaphragm and attached the liver ventral body wall
  • round ligament: remnant of foetal umbilical vein
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4
Q

Hepatic blood circulation

A
  • blood supply of the liver unusual because it has a dual blood supply
    liver receives:
  • arterial blood from the hepatic artery
  • from the hepatic portal vein (from small intestines) - all toxins are taken out at the liver before the blood goes back
  • branched of hepatic portal vein and hepatic artery empty together and mix in the liver sinusoids
    blood leaves liver:
  • through hepatic vein -> inferior vena cava
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5
Q

Hepatic arterial circulation

A
  • liver received approx. 30% arterial blood from the hepatic artery
  • highly oxygenated
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6
Q

Hepatic (liver tissue) portal system

A
  • liver receives 70% venous blood from organs of the gastrointestinal tract and spleen through the hepatic portal vein
  • contains nutrients absorbed from the GI tract
  • Oxygen poor
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7
Q

Blood supply of the liver - the liver as a filter

A
  • Liver functions as a filter to remove potentially harmful xenobiotics
  • Xenobiotics: chemical compounds that are foreign to a living organism = not normally naturally produced by or expected to be present within the organism
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8
Q

Microscopic anatomy of the liver

A
  • Liver lobules: hexagonal structural and functional units
  • Hepatocytes (liver cells) filter nutrient-rich blood, produce bile
  • central vein located in longitudinal axis
  • central vein for the blood vessels and nerves
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9
Q

Hepatocytes = liver cells

A
  • make up about 80% of the cells in the liver (others can be white blood cells)
  • filter and process nutrient-rich blood
  • increased rough and smooth ER, golgi, peroxisomes and mitochondria
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10
Q

Hepatocyte functions

A
  • produce 900mL bile/day
  • produces blood nutrients
  • store fat-soluble vitamins (fat storage)
  • perform detoxification
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11
Q

portal triad

A
  • not necessarily a triad at each corner of the hexagon, but it was what called when it was thought to have 3
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12
Q

5 parts in each corner of portal triad contain

A
  1. branch of hepatic artery, which supplies oxygen (from the heart)
  2. branch of hepatic portal vein, which brings nutrient-rich blood from intestine
  3. bile duct, which receives bile from bile canulicali
  4. lymphatic vessels
  5. a branch of the vagus nerve
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13
Q

Microscopic anatomy of the liver

A
  • liver sinusoids (liver blood vessels): leaky capillaries between hepatic plates
  • blood enters liver lobules through branched of hepatic portal vein and hepatic artery empty together and mix in the sinusoids
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14
Q

Stellate macrophages

A
  • hepatic macrophafes = kupffer cells
  • line walled of liver sinusoids
  • star-shaped, phagocytic
  • phagocytose invading agents
  • remove debris and old red blood cells
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15
Q

Bile

A
  • dark green/yellow fluid due to chemicals within and their composition
  • produced by the liver hepatocytes
  • collected in lobule canulicali (= bile capillaries)
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16
Q

Bile consists of

A
  1. water = 97%
  2. bile salts = 0.7%, fat emulsification and absorption
  3. bilirubin = 0.2%
  4. fats (cholestrol) = 0.5%
  5. electrolytes (the rest)
17
Q

Bile enterohepatic circulation

A
  • 95% of secreted bile salts are recycled
    1. reabsorbed into blood by ileum
    2. returned to liver via hepatic portal blood -> only 5% newly synthesised
    3. re-secreted in newly formed bile
  • after being produced, stored in gall bladder. Then once eating occurs, the bile is released and goes through pancreatic duct into the ileum
18
Q

Function of bile in digestion

A
  • fat is water repellent, but enzyme responsible for fat digestion (lipase) is water soluble
  • bile salts emulsify (mix of water and oils to the point where it looke like one) fats in the intestine
  • they surround fat droplets to from micelles, providing a greater surface area for pancreatic lipase to break down the fat
19
Q

The gallbladder definition

A
  • a thin-walled muscular sac
  • attached to visceral layer of the liver = on ventral liver surface
  • received and stored bile from the liver via the hepatic and then cystic duct
  • muscular contractions released bile via cystic duct, which flows into the bile duct
20
Q

the gallbladder

A
  • lined by a simple columnar epithelium
  • functions to store and concentrate bile by absorbing water and ions
  • can store 50-100mL in humans
  • contains many honeycomb folds that allow it to expand as it fills
21
Q

Functions of a healthy liver: metabolism

A

carbohydrates, amino acids and fats

22
Q

Functions of a healthy liver: energy homeostasis via

A

glycogenesis, glycogenolysis, gluconeogenesis, ketogenesis, repackaging excess FA

23
Q

Functions of a healthy liver: synthesis and secretion of

A

albumin, plasma proteins, clotting factors, transport proteins, insulin-like growth factoe-1, cholestrol, bile salts, glutathione

24
Q

Functions of a healthy liver: storage of

A

glycogen, vitamin A, vitamin B12, iron, copper

25
Q

Functions of a healthy liver: purification transformation and clearance of:

A

toxins, drugs, hormones, ammonia -> urea, bilirubin

26
Q

the pancreas

A
  • no distinct capsule, but covered by a thin layer of loos connective tissue
  • location: mostly retroperitoneal, deep to greater curvature of stomach
  • head is encircled by duodenum
  • tail touches spleen
27
Q

Exocrine functions of pancreas (basic)

A

produces pancreatic juice

28
Q

Endocrine functions of pancreas (basic)

A
  • secretion of insulin and glucagon by pancreatic islet and cells = islets of Langerhans
  • clumps of secretory cells supports by reticulin fibres, and containing fenestrated capillaries
  • delicate capsule arounf each islet
  • paler than the surrounding exocrine cells due to less rough endoplasmatic reticulum
  • isles do not have an acinar organisation
  • endocrine pancreas is made up of clusters of cells called islets of langerhans
29
Q

the endocrine pancreas - islets of Langerhans

A
  • islets cells: 3 secretory cell types:
  • 20% alpha - secrete glucagon
  • 75% beta - secrete insulin
    (insulin stimulates the synthesis of glycogen, protein and fatty acids)(facilitates the uptake of glucose into cells and activated glucokinase in liver)
  • 5% delta - secrete somatostatin
    (locally acting hormone which inhibits other endocrine cells)
30
Q

The exocrine pancreas

A
  • closely packed serous acini= clusters of secretory cells
  • produce zymogen granules containing proenzymes
  • secrete an enzyme rich alkaline fluid into the duodenum via the pancreatic duct
  • the alkaline pH is due to the presence of bicarbonate ions, and helps to neutralise the acid chyme from the stomach, as it enters the duodenum
  • the enzymes digest proteins, carbohydrates, lipids and nucleic acids
  • > ducts: secrete to duodenum via main pancreatic duct
  • > smaller duct cells produce water and bicarbonate
31
Q

Secretions of the exocrine pancreas

A
  • secretions of the acini empty into ducts lined with a simple low cuboidal epithelium, which becomes stratifies cuiboidal in the larfer ducts
32
Q

what is secreted of the exocrine pancreas

A
  1. proteases: digests proteins, secreted in inactive form to prevent self-digestion
  2. lipases: digests fats
  3. amylase: digest carbohydrates
  4. bicarbonate: neutralises chyme
33
Q

Structure of the enzyme - producing tissue of the pancreas

A

DIAGRAM

34
Q

Pancreatic juice composition and role in digestion

A
  • 1200-1500mL produced daily containing: watery, alkaline solution (pH 8), electrolytes, primarily HCO3-
    1. neutralises gastric acid and acidic chyme in duodenum
    2. enzymes to break down protein (protease), fat (lipase), starch (amylase) and nucleic acids (nucleases
    3. suppresses gastric acid secretion
35
Q

Enzyme-producing tissue of the pancreas - histology

A

DIAGRAM

36
Q

Activation of pancreastic proteases in SI

A

DIAGRAM

37
Q

Bile and pancreatic secretions into the small intestine

A
  • bile duct and pancreatic duct unite in wall of duodenum
  • fust together in the bulblike structure called heaptopancreatic ampulla
  • ampulla opens into duodenum via volcano-shaped majoy duodenal papilla
  • hepatopancreatic sphincter controls entry of bil and pancreatic juice into duodenum
38
Q

Control of secretion

A
  • bile and pancreatic juice secretions are both stimulated by neural and hormone controls

Anat and Phys (19 decks)

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