Digestive System (From Small Intestine)

Front 1

Small Intestine

Back 1

- Major events of digestion and absorption
- Approximately 90% of digestion and absorption occur in small intestine
- Begins at pyloric sphincter of stomach
- Coils through central and inferior part of abdominal cavity and opens into large intestine

Front 2

Divisions of the Small Intestine

3

Back 2

- Duodenum ( shortest)
- Jujunum
- Ileum ( longest )

Front 3

Wall of the Small Intestine

Back 3

Wall structure same except
- Circular folds/ plicae circulares :
- Permanent ridges in the mucosa
- Begin near proximal portion of duodenum and end at mid ileum
- Increase surface area and cause contents to spiral through lumen of small intestine

Front 4

Villi

Back 4

- Finger like projections of mucosal layer ( millions)
- Increase surface areas of epithelium available
- For absorption and digestion
- Gives lumen feathery/ or velvety appearacne radiographically

Front 5

Embedded in tissue are:

4

Back 5

- An arteriole, venule, capillary network and LACTEAL ( lyphatic capillary)

Front 6

Where are nutrients absorbed?

Back 6

- through epithelial layer into blood and lymph vessels of villi

Front 7

Mucosa contains cavities :

Back 7

- Cells lining cavities from intestinal glands ( crypts of lieberkuhn) and secrete intestinal juice

Front 8

Wall of the Small intestine

Back 8

- Several types of cells line small intestine:
- Free surface has microvilli: brush border
- Increase membrane surface area and ability to absorb

Front 9

Goblet cells

Back 9

- Produce and secrete muscous for lubrication

Front 10

Enteroendocrine cell Hormones

3

Back 10

- Secreti
- Cholecystokinin
- Gastric inhibitory peptide

Front 11

Cholecystokinin

Back 11

- hormone carried by blood to G.B

- Stimulates GB to contract and empty bile into duodenum

Front 12

Paneth cells

Back 12

- Secrete a bactericidal enzyme and capable of phagocytosis

Front 13

Lymphatic tissue

Back 13

- Solitary lymphatic nodules: Distal part of lumen
- Aggregated lymphatic follicles ( Peyer's patches) most numerous in terminal ileum

Front 14

3 types of secretions

Back 14

- Convey to small intestine and mix with chyme
1) Bile
2) Pancreatic juice
3) Intestinal juice

Front 15

Functions of the Small Intestine

Back 15

Provides onward movement of contents by
- Segmentation and peristalsis

Front 16

Segmentation

Back 16

- Localized contractions in areas containing food

- Mixes chyme with digestive juices
- Brings particles of food into contact with mucosa for absorption

Front 17

Peristalsis

Back 17

- Waves of muscular contractions move along wall of intestine pushing contents ahead of each wave

Front 18

Large Intestine

Back 18

- Large intestine terminal portion of the GI tract
- Overall functions
- Completion of absorption
- Production of certain vitamins
- Formation of feces
- The expulsion of feces from the body
- No digestive enzymes secreted
- Secretes mucus to lubricate passage

Front 19

Divisions of the Large Intestine

Back 19

- Cecum
- Appendix
- Ascending colon
- Rt. Colic flexure/ hepatic flexure
- Transverse colon
- Lt colic flexure / splenic flexure
- Descending colon
- Sigmoid colon
- Rectum
- Anal canal- anus

Front 20

Muscularis

Back 20

Teniae coli:
Haustra:
Semilunar folds
Microanatomy:

Front 21

Teniae coli

Back 21

- 3 bands of longitudinal muscle fibers situated @ even intervals around colon

Front 22

Haustra

Back 22

- Sac like pouches
- Result of teniae coli

Front 23

Semilunar folds

Back 23

- Folds of inner mucous lining of large intestine b.t haustra

Front 24

Microanatomy:

Back 24

- Mucosa

Front 25

Mucosa

Back 25

- Simple columnar epithelium
- Contains absorptive and goblet cells
- Lack microvilli and do not secrete enzymes

Front 26

Digestive Process in the Large Intertine

Back 26

- Haustral churning
- Peristalsis
- Bacteria in large bowel alter contents
Producing gas &Some vitamins
- Some water absorption takes place

Front 27

Liver accessory organ of digestion

Back 27

Largest gland of body
Approx 1.4 kg ( 3lbs ) in adult
- Inferior to diaphragm
- Occupies most of right upper quadrant
- Under the dome of diaphragm
- Lower edge of normal sized liver level with lower margins of ribs

Front 28

Structure of the Liver

Back 28

- Fibrous capsule encloses the liver
- Connective tissue divides organ into a large right lobe and a smaller left lobe
- Falciform ligament

Front 29

Falciform ligament

Back 29

- A fold of parietal peritoneum that separates liver lobes
- Fastens liver to abdominal wall anteriorly and diaphragm
- Remnant of umbilical vein in fetal circulation

- Free border of falciform ligament called : LIGAENTUM TERES ( round ligament)

Front 30

Minor lobes of the Liver:

2

Back 30

- Quadrate lobe ( near gall bladder)
- Caudate lobe ( close to the vena cava)

- Lobes divided into lobules

Front 31

Blood form hepatic artery and portal vein passes through:

Back 31

- liver sinusoids

Front 32

Liver Sinusoids

Back 32

Highly permeable capillaries
- Where blood comes in contact with liver cells
Blood flows to hepatic veins and then IVC
Bile canaliculi collect bile secreted by liver cells

Front 33

Liver Sinusoids Unit and form:

Back 33

- Right and left hepatic ducts
- Drains bile from liver

Front 34

Functions of the Liver

Back 34

Carbohydrate metabolism
- Maintenance of blood glucose levels
Lipid metabolism
Protein metabolism
Removal of drugs and hormones
- Detoxifies
Excretion of bile
Synthesis of bile salts
Storage

Phagocytosis

Front 35

The Liver Stores:

Back 35

- Glycogen
- Vitamins ( A, B12, D,E,K) and
- Minerals

Front 36

Phagocytosis (reticuloendothelial cells)

Back 36

- Phagocytize word out red and white blood cells and some bacteria
- Activation of vitamin D

Front 37

Gallbladder

Back 37

- Hollow, pear shaped sac located in depression on inferior surface of liver: RUQ
Capacity of 30- 50 milliliters
Mucosa arranged in rugae
Lacks a submucosa

Front 38

Muscularis of smooth muscle

Back 38

- Contacts by hormonal stimulation
- Contents from gallbladder

Front 39

Function of Gallbladder

Back 39

- Stores bile bt meals
- Concentrates bile by reabsorbing water
- Releases bile into duodenum when stimulated by cholecystokinin from the small intestine

Front 40

Common bile duct

Back 40

- formed by union of common hepatic and cystic ducts
- Leads to duodenum where the hepatopancreatic sphincter remains contracted
- Bile collects in common bile duct
- Backs up into cystic duct
- Bile flows into GB where it is stored

Front 41

Bile

Back 41

- Salts in bile act as detergent to emulsify fats into small drops
- Partically an excretory product
- Partially a digestive secretion
- Bile salts aid in absorption of lipids following digestion

Front 42

Bile Flow

Back 42

- Secreted by liver cells
- Conveyed by the bile canaliculi
- Passes out of liver via
---> Right and left hepatic ducts
---> Enters the biliary apparatus
- Bile enters and leaves GB through cystic duct
- Bile leaving GB joins the common bile duct &
- Joins pancreatic duct to form HEPATOPANCREATIC AMPULLA ( ampulla of vater)
- Fatty foods stimulate hormone release activating GB contraction and
- Forcing bile into descending duodenum

Front 43

Pancrease

Back 43

- Soft oblong gland ( retroperitoneal)
- Mixed gland : both exocrine and endocrine parts

Front 44

Divisions of the Pancrease

3

Back 44

- Head
- Body
- Tail

Front 45

Head of the Pancreas

Back 45

- Lies within the c loop of the duodenum

Front 46

Body of the Pancreas

Back 46

- Posterior to the antrum of the stomach

Front 47

Tail of the Pancreas

Back 47

- Caudal to the body of the stomach

Front 48

Pancreatic duct ( duct of wirsung)

Back 48

- Joins common bile duct and
- Enters duodenum at hepatopancreatic ampulla ( ampulla of vater)

Front 49

Endocrine part of Pancreas

Back 49

Glands of internal secretion, ductless,
- Pass into blood
- Secretes hormones ( glucagon and insulin)- pancreatic islets or islets of langerhands
Secretes insulin directly into blood capillaries
Concerned with sugar metabolism
- Breaks down sugar
- Not enough insulin with result in diabetes
Secretes glucagons
- Accelerates breakdown of glycogen into glucose in liver
- Releasing glucose into blood as body needs it
- Raises blood sugar levels

Front 50

Exocrine part of Pancreas

Back 50

Small ducts drain pancreatic juice into main pancreatic duct
Joins common bile duct ( CBD)
- Form liver and gall bladder
Secrete enzymes and pancreatic juice
Forms common opening ( hepatopancreatic ampulla) opens into duodenum
Delivers pancreatic juice into duodenum

Front 51

abdominal aorta

Back 51

- extends from diagram (T12) to the L4 vertebra and bifurcates into the rt and lt common iliac arteries

Front 52

Un-paired Branches

3

Back 52

Celiac trunk or axis "trifurcated " into :
- Lt gastric artery - supplies stomach and esophagus (s)
- Splenic artery - largest of the three (L)
- Common hepatic artery - arises from RT side (m) at the level of the T12-L1

Front 53

Superior mesentreric

Back 53

- arises apprx. 1 cm inferior to celiac @ the level of L1- anastomoses extensively and has 5 branches- supplies the small intestine and 1/2 of colon

Front 54

Paired Branches

5

Back 54

- Phrenic artery to diaphragm
- Suprarenal arteries to suprarenal glands at L1 just sup. To renals
- Renal arteries to kidneys @ L2
- Gonadal arteries to testes or ovaries also @ L2 just inferior to renal arteries
- Terminal division- two common iliac arteries at the level of L4

Front 55

Anastomoses

Back 55

- alternate routes called collateral circuits for blood to reach a particular organ or tissue- detours for arterial blood

Front 56

Inferior mesenteric

Back 56

- arises approx L3 and anastomoses extensively & has 3 branches that supplies the distal half of the colon

Front 57

Portal Circulation

Back 57

- Route - abdominal aorta to branches in abdomen to capillaries of digestive organs to veins - SMV and SV that join to the HEPATIC PORTAL VEIN! To liver capillaries to hepatic vein to IVC
- The superior mesenteric vein and the splenic vein drain blood from the organs of digestion
- They join to form the hepatic portal vein
- Which enters the liver
- Breaks up into capillaries- delivers nutrient rich blood to liver sinusoids
- Which then re-unite to form the hepatic vein
Which then leads the liver and empties into IVC

Front 58

Before nuetrients enter blood stream:

Back 58

- The liver stores some of the nutrients and modifies others before they pass into the general circulation
- Blood carrying the products of digestion MUST make a "pit stop" at the liver before entering the general blood stream