histology- the digestive tract

Question 1

what is liver and pancreas composed of

Answer 1

glandular epithelial cells

Question 2

functions of the liver

Answer 2

most divers tissue in the body
detoxification of metabolic waste products, toxins and drugs
synthesising cholesterol, bile

etc
varied

Question 3

portal vein

Answer 3

capillary bed at one end and at the other end

Question 4

how fast reaches the liver

Answer 4

thoracic duct dumped into venous circulation

Question 5

porta hepatis

Answer 5

groove a deep fissure in the inferior surface of the liver through which all the neurovascular structures (except hepatic veins) and hepatic ducts enter or leave the liver

Question 6

incoming blood

Answer 6

arrives in segments in different place to where the outgoing blood drains

Question 7

liver capsule

Answer 7

covered by collagenous connective tissue

Question 8

liver structure

Answer 8

made up of segments called lobules
each lobule if approximately hexagonalk and has a branch of the hepatic vein called the centrolobular vein (central vein) at its centre and portal triads at each corner

Question 9

sinusiods

Answer 9

blood hyperfrolirates till gets into central veins

Question 10

blood entering in portal tracks

Answer 10

spill into all the different lobules

Question 11

difference between human and pig lung

Answer 11

pig doesn’t have clear connective tissue septa between lobules

Question 12

portal triad

Answer 12

branches of the vessels which enter at the porta hepatis that is the hepatic portal vein and the hepatic artery. They are also called the portal triad because they also include a third ‘tube’, a branch of the conduit which leaves the liver at the porta hepatis, the bile duct.

Question 13

what does portal tracts include

Answer 13

branches of
hepatic portal vein
heptatic artery
bile ductale- lined by simple cuboidal cells called cholangiocytes

tracts also typically include lymphatic vessels

Question 14

lymph producer

Answer 14

liver largest producer in the body

large structure with lots of fluid

can see thin walled lymphatic vessels in lab

Question 15

looking for bile ducts on cells

Answer 15

cuboidal cells

Question 16

hepatocytes

Answer 16

main cells of the liver
these polyhedral epithelial cells form what appear in sections to be cords of liver cells but in fact are plates or sheets of cells with spaces in between for blood to flow through
these blood channels are called sinusoids

Question 17

the lobule

Answer 17

classic lobules- centred on central veins surrounded by triads
liver acinus- two portal tracks in centre of attention
when toxins enter body arrive at this point so good to see as a way of understanding how liver works

Question 18

direction of blood flow

Answer 18

central vein- 5 triads surrounding it and blood flows towards each of the 5 triads

Question 19

sinusoids ultrasound

Answer 19

sinusoids are lined by endothelial cells- sit slightly away from hepatocytes- space is called the space of disse or the perisinusiodal space
microvilli of the hepatocytes project into this space

Question 20

hepatocytes and sinusoidal ultrasound

Answer 20

stuffed with mitchocondria need energy

Question 21

connective tissue of the liver

Answer 21

place of disse- find type 1 collagen

portal tracts

Question 22

hepatic stellate cells

Answer 22

also called ito cells
found scattered in the space of disse
modifies fibroblasts and make connective tissue
also store vitamin A within fat droplets in their cytoplasm
in some pathological conditions they transform into myofibroblasts and produce scar tissue in the liver

Question 23

Kupffer cells

Answer 23

these are resident macrophages scattered within the sinusoids

they act to remove particulate matter from the blood and help remove worn out red blood cells

Question 24

bile

Answer 24

an alkaline solution containing water, ions, phospholipids, bilirubin and bile salts

all heaptocytes produce bile

Question 25

bilirubin

Answer 25

a pigment which results from the breakdown of hemoglobin in the spleen, and when excreted in the bile, is the principal cause of the brown colour of feces.

Question 26

the bile salts

Answer 26

necessary for the emulsification of fats in the digestive tract. Primary bile that is produced by the hepatocytes is modified in several ways (e.g. addition of bicarbonate ions and water) by the cholangiocytes, the cells that line the biliary tree.

Question 27

bile travel

Answer 27

Bile flows via bile canaliculi toward the bile ducts in the portal tracts and thence to the hepatic ducts.

Question 28

bile canaliculi

Answer 28

small channels (1µm dia.) formed by tight junctions in the cell membranes of adjacent hepatocytes

Question 29

gall bladder

Answer 29

a muscular sac which is
lined by simple columnar epithelial backed by a lamina propria of loose connective tissue rich in blood vessels and lymphatic vessels, a coat of smooth muscle and an outer collagenous layer of adventitia.
Stores bile.
Has a folded mucosa when empty – this flattens when distended.
Modifies the bile stored within it.

Question 30

volume of bile arriving from the liver

Answer 30

About 80%-90% of the volume of the bile arriving from the liver is removed by the gall bladder. This is done by actively pumping Na and Cl ions from the bile into the spaces between adjacent epithelial cells. Water then follows due to the increase in osmotic pressure in these spaces, which become distended with fluid when the gall bladder is actively concentrating bile. The water is carried away, largely by the lymphatic vessels of the lamina propria.

Question 31

gall balder contraction

Answer 31

The gall bladder is stimulated to contract and deliver bile to the duodenum, both under nervous control (chiefly vagal), and via release of the hormone cholecystokinin by endocrine cells of the duodenum when fatty food enters it.

Question 32

cholecystitis

Answer 32

inflammation of the gall bladder is not uncommon. Here gallstones have obstructed the cystic duct leading to expansion of the gall bladder, thickening of the muscle layers and inflammation

Question 33

pancreas

Answer 33

both and exocrine and an endocrine gland

.

Question 34

pancreas endocrine gland

Answer 34

The endocrine pancreas consists of small, scattered islands of tissue called islets of Langerhans, which produce a number of hormones including insulin and glucagon. Islets make up about 1%-2% of the pancreas

Question 35

pancreas exocrine gland

Answer 35

The exocrine pancreas produces about a litre of digestive juices containing proteases to break down proteins, lipases to break down lipids, nucleases to breakdown DNA/RNA, amylase to break down starch, etc, each day. These enter the duodenum via the pancreatic duct

Question 36

pancreas on microscope

Answer 36

thin connective tissue capsule that is continuous with connective tissue septa that divide the glands into lobules

Question 37

exocrine cells

Answer 37

basal part- typically basophilic- more purple due to extensive RER

apical part- eosinophilic- prescience of zymogen (pre-enzyme granules)

Question 38

centroacinar cells

Answer 38

duct cells within the acini

smallest ducts doesn’t begin at end of acinus but in the middle of the acinus and carries on

Question 39

he hepatopancreatic ampulla (of Vater).

Answer 39

The main pancreatic duct joins the common bile duct and opens into the duodenum on a papillae: