Histology - Intestines

Front 1

Functions of Small Intestines (2)

Back 1

1) Digestion completed
2) Absorption of Nutrients

Front 2

How is its surface area maximized for optimal absorption? (look at handout) (5)

Back 2

1) Length is about 15-20 feet in humans
2) Valves of Kerckring AKA plica(e) circular(es) (circular folds)
3) Villi
4) Crypt of Lieberkuhn - are the invaginations on the circular folds
5) Microvilli - brush border

Front 3

Layers of Small Intestine (From top to bottom)

Back 3

Lumen, circular folds, submucosa (Meisnner's Plexus underneath), muscularis mucosae, muscularis propia (made up of circular, longitudinal - auerbach in these layers, stimulates peristalsis), celom serosa

Front 4

Epithelium Type of the Small Intestine and the 5 Cell types found

Back 4

Simple Columnar
1)Enterocytes
2)Goblet Cell
3)Paneth Cell
4) Endocrine Cell
5) M-Cell

*only cells 1-3 are seen in lab

Front 5

Enterocyte (5)

Back 5

-makes up brush border
-absorbs digested nutrients
-has some digestive enzymes projecting from cell membrane = "surface digestion
-considered another place of holocrine secretion
-some are found squeezed between goblet cells
-produced in the crypts via cell division and then travels up to the villus when it assumes its mature structure.

Front 6

Goblet Cell

Back 6

Has 1 Function - MUCUS
-it is the main mucus producer in the small and large intestine.
-when you get to the jejunum, they are very abundant
-as you move down the small intestine in general they become very abundant
-can have the same microvilli, but not significant enough to produce a brush border
-both this and enterocytes are located in the top portion of the small intestine called the villus, which also has a lot of lymphocytes; almost looks like lymphatic tissue
-produced in the crypts and then travels up to the villus when it assumes its mature structure.
-produced in the crypts via cell division and then travels up to the villus when it assumes its mature structure.

Front 7

Paneth Cell (4)

Back 7

are granules, found in the base (bottom) of the crypts aka the bottom portion of the small intestine (look at handout), the crypts can be used as ducts and contain GALT (lots of clusters of lymphocyted),
stem cells are also found here
-secretes anti-microbial peptides (enzymes) called defensins.
-The paneth cell has its own activator
-also secretes trypsin, which is involved in the cleavage and activation of the defensins made by paneth cells.
-might be trying to protect the stem cells through its secretions.

Front 8

Endocrine Cell (2)

Back 8

releases two hormones:
1) CCK
2) Secretin

Front 9

M-Cell

Back 9

Is a cell of the immune system (look at handout). If an antigen/virus comes in contact with the intestinal epithelium, M cells pass the antigen onto macrophages and B cells, which then create antibodies to neutralize the antigen. The M cells import bacteria into the dome region of the GALT where dendritic cells engulf the microbes and transfer them to B and T cells.

Front 10

In what organs are glands in the submucosa found

Back 10

Not in the stomach nor the colon. The only other gland that has glands in the submucosa are the duodenum and esophagus (so far in these slides, the duodenum and jejunum have been described)

Front 11

Lamina propria

Back 11

It runs from the muscularis mucosae towards the villus. It is composed of strands of smooth muscle used for contraction

Front 12

Brunner's Glands

Back 12

-are invovled with mucus
-are found in the submucosa of the duodenum, above the muscularis propia

*must identify duodenum on lab exam, but for jejunum and ileum you can just say small intestine

Front 13

Acidic Chyme

Back 13

It is squirted into intestines via pyloric sphincter from the stomach. This acidity must be neutralized, which is done by the Brunner's glands

Front 14

Portal Veins

Back 14

begin and end in capillaries w/o going through the heart. will see a lot of them in today's slides

Front 15

Final Products of proteins, cb's, and fats, and where they are sent to

Back 15

proteins --> amino acids and small peptides
cb's --> monosaccharides (glucose)
fats (triglycerides --> glycerol & fatty acids. also broken down into fatty acids & monoglycerides, which are both preferentially sent to the lymphatic vessel (aka Lacteals) which go to the liver.
-Most of the final products are sent through the hepatic portal vein to the liver

Front 16

Hepatic Portal Vein

Back 16

Goes to the liver, from which the hepatic vein emerges, which goes to the heart

Front 17

Large Intestine - Colon (4)

Back 17

-No villi are found here.
-Have very long crypts of Lieberkuhn
-Enterocytes and goblet cells are found here, goblet cells are needed so that they can lubricate its lining so that hard, undigested material in the large intestine can be moved out of the body via the anus, which is stratified squamous.
-lots of water is found here, which the enterocytes reabsorb