Digestive Part II - slides 1 - 68 Flashcards
Heaviest gland of the body?
Liver (3lbs)
Largest INTERNAL organ of the body?
Liver
Located inferior to the diaphragm, the Liver occupies most of the ___ _____ and part of epigastric region
Right Hypochondriac region
The Liver, almost completely covered by visceral peritoneum
Divided into two principal lobes by the ___ ____
Falciform Ligament
Which lobe of the Liver is smallest?
Right lobe Largest
Left lobe smallest
The Liver receives blood from two sources:
Hepatic artery (25%) – oxygenated blood
Portal vein (75%) – deoxygenated blood + nutrients
These compose the ___ ___:
- Bile ducts inside the liver
- Common hepatic duct (outside of the liver)
- The gallbladder and its cystic duct
- Common bile duct
- Ducts of the pancreas
Biliary Tree
Functions of the Biliary Tree: (3)
- Make, store, and secrete bile
- Rids liver (and body) of some waste products
- Aids in digestion of foods in small intestine
Major functional unit of the Liver:
Hepatic Lobules
Hexagonal in shape
Comprise rows of hepatocytes
Perform a wide array of metabolic, secretory, and endocrine functions
Hepatic Lobules
Found in the corners of the Hepatic Lobules:
Portal Triads
These all comprise ___ ____:
- A bile duct (flows away from central vein)
- Branch of hepatic artery (flows toward central vein)
- Branch of portal vein (flows toward central vein)
(see slide 7)
Portal Triads
Specialized epithelial cells interspersed throughout the liver
Make up ~80% of the mass of the liver
Hepatocytes
Forms a crucially important cell layer that separates sinusoidal blood from the canalicular bile
Hepatocytes
Location of synthesis of:
- Many transport proteins like albumin, and fibrinogen
- Lipoproteins, fatty acids, triglycerides
- Cholesterol
- Bile
Hepatocytes
Highly permeable blood capillaries between rows of hepatocytes
Hepatic Sinusoids
Hepatic Sinusoids:
Receives oxygenated blood from branches of ___ ___
Receives nutrient rich deoxygenated blood from the ___ ___
Hepatic Artery
Portal Vein
Fixed phagocytes found within sinusoids that help “clean” blood
Destroy worn-out red and white bloods cells, bacteria, and other foreign matter
Stellate reticuloendothelial (Kupffer) cells**
Functions of the Liver:
- Carbohydrate (starch) metabolism
- Lipid Metabolism
- Protein Synthesis
- Processes Drugs and -Hormones
- Excretion of Bilirubin
- Storage
- Phagocytosis
- Bile Synthesis
…further explained in other cards
Carb Metablolism:
Plasma glucose is low:
Glycogenolysis
Carb Metabolism:
Plasma glucose is high:
Glyconegesis
What function of the Liver involves:
Synthesizes and stores some triglycerides
Synthesizes certain lipoproteins
Synthesizes some cholesterol
-Adds some cholesterol to bile to aid in lipid metabolism
Lipid Metabolism
Bilirubin is reabsorbed from broken down RBC’s and excreted in the ___ produced within the liver
Bile
Most of the bilirubin in bile is metabolized in the __ ___ by bacteria and eliminated in feces
Small Intestine
In addition to glycogen, liver is prime site for storage of certain vitamins such as __, __, __, __ , __,
Also stores certain minerals such as ___ and ___.
These are all released when needed by the body
A, B12, D, E, K
Iron and Copper
The stellate reticuloendothelial (Kupffer) cells phagocytize aged RBC’s, WBC’s and some bacteria
Liver function: Phagocytosis
Bile synthesis involves the mixture of bile salts, ____ and ____
Bile Pigments and Cholesterol
Each day about how much bile is synthesized and secreted by hepatocytes:
600 - 1000mL
Bile is stored and concentrated in the:
Gallbladder
Bile is a yellow, brownish, or olive-green liquid
pH of ___-___
Plays important role in fat digestion and absorption
Serves as a means for excretion of waste products from blood (i.e. ____)
pH 7.6 - 8.6
i.e. blilirubin
Pear-shaped sac
Located in a depression of the posterior/inferior aspect of the liver
Gallbladder
Stores and concentrates bile made by the liver (up to 10x’s more concentrated)
Water and ions are reabsorbed by the ___ walls
Gallbladder
Between meals, bile is made and released by liver into common hepatic duct and down into ___ ___ ___
It accumulates here and starts to flow into the gallbladder when the ducts are full
Common Bile Duct
Large part of the immune system, tissue repair, Hematopoiesis, and RBC and Platelet destruction are functions of the ____
Spleen
As blood passes through sinusoids within ____, macrophages remove microorganisms and destroy them
Spleen
Monocytes and lymphocytes complete their development and become activated
During fetal development, RBC’s are also formed in the spleen
After birth, RBC’s only developed here in extreme cases of anemia
Hematopoiesis
Spleen Function:
Macrophages remove old RBC’s and imperfect platelets
Breaks apart the hemoglobin molecule to salvage the ___ and ___ for reuse
Iron and Globin
Where most digestion and absorption of nutrients occurs
Small Intestines
Small Intestines:
The length alone allows for a large surface area, but inside that length folds, ___ and ___ allow for even more surface area
Villi and Microvilli
Small Intstine begins immediately after the pyloric sphincter of the stomach
Ends at the ___ ___ (valve) where the large intestine begins
Length is ~10 ft in a living person
Diameter is ~1in
Ileocecal Sphincter
3 regions of small intestine:
Duodenum
Jejunum
Ileum
the shortest region, 10in
Retroperitoneal
Starts after pyloric sphincter, merges with jejunum
Duodenum
3 feet long
Starts at the end of duodenum and extends to the ileum
Jejunum
the longest region, 6 feet long
Starts at the end of the jejunum and extends to ileocecal sphincter (valve) merging with the large intestine
Ileum
AKA – Suspensory Ligament of the Duodenum
Ligament of Treitz
Important landmark as it signifies the anatomical difference between Upper GI and Lower GI
Ligament of Treitz (suspensory ligament of duodenum)
In the small intestine: Is actually a “suspensory muscle” covered by a fold of the peritoneum
Begins at the diaphragm, connects to the duodenojejunal flexure (DJ) suspending it upwards
Ligament of Treitz (supsensory ligament of Duodenum)
Important landmark as it signifies the anatomical difference between Upper GI and Lower GI
Ligament of Treitz (suspensory ligament of Duodenum)
Except for a minor portion (proximal aspect) of the duodenum, the small intestines are completely covered by ____ (visceral peritoneum)
Serosa
The ____ layer of small intestine
Contains the Myenteric plexus (Plexus of Auerbach) in between
Muscluaris
Contain Brunner’s glands that secrete alkaline mucous that neutralizes gastric acid in chyme
Also Contains the ____ nerve (Meissner’s) plexus
Submucosa Layer of Small Intestines
Submucosal
Contains layer of epithelial cells, lamina propria, muscularis mucosae
see slide 29/30
Mucosa of Small intestines
Deep crevices in the mucosal lining called intestinal glands (crypts of ____)
These crypts are lined with numerous types of cells with different functions
Crypts of Lieberkuhn
Sm. Intestine Mucosa: Miscellaneous Cells (which absorb/secrete_ -Enterocytes -Goblet -Paneth
Absorptive (Enterocytes): absorbs nutrients from chyme
Goblet Cells: secrete mucuous
Paneth cells: Secrete Lysozome (bactericidal enzyme, capable of phagocytosis)
Sm. Intestine Mucosa:
Enteroendocrine Cells:
- Secretes secretin
- Stimulates pancreatic juice flow
- Inhibits gastric juice flow
S Cells
Sm. Intestine Mucosa:
Enteroendocrine Cells:
- secretes cholecystokinin (CCK)
- Helps satiety (feeling full)
- Stimulates pancreatic juice flow
- Relaxes sphincter of Oddi
- Stimulates gallbladder contraction
CCK Cells
Sm. Intestine Mucosa:
Enteroendocrine Cells:
- secretes glucose dependent insulinotropic polypeptide (GDIP)
- AKA gastric inhibitory polypeptide (GIP)
- Decreases the rate at which gastric emptying occurs
K Cells
Begin near proximal portion of duodenum, end near midportion of ileum
Some extend circumferentially, others only part way
Increases surface area for absorption
Causes chyme to spiral, allowing for more dissolution
Circular Folds (Plicae Circulares)
Permanent ridges about 10mm in length
Vastly increases surface area
Gives the mucosal lining of small intestines a velvety appearance
20-40 per square millimeter
Villi (fingerlike projections in mucosa about 1-5mm long)
When viewed even through a microscope, they are seen as a fuzzy border, this is called the brush border
Estimated 200million microvilli per square millimeter
This brush border also produces several enzymes that have digestive functions
Microvilli - projections of apical membrane of absorptive cells
When ____ enters the small intestine, it contains partially digested carbohydrates, proteins and lipids
The digestion of the rest of this is a collaborative effort by pancreatic juice, bile, and intestinal juices
Chyme
~1 – 2 liters of intestinal juice is secreted each day
Clear, yellow liquid
Slightly alkaline at pH of __(#)
pH 7.6
Cells within the microvilli synthesize several digestive -____ enzymes called ___=
These cells slough off every 5-7 days into the luminal contents
They break apart and release enzymes to help digest nutrients in chyme
Brush-border enzymes
What percent of absorption occurs in the small intestine:
90%
Once chyme enters the small intestine, the leftover carbohydrates are digested by pancreatic ____
It has no effect on cellulose (indigestible fiber)
Large component of feces
After ____ (whether salivary or pancreatic) has split carbohydrates into monosaccharide molecules, they become absorbable
Amylase
Pancreatic juices – trypsin, chymotrypsin, carboxypeptidase, and ____ continue protein digestion
Digestion of proteins ends with single or small chains of amino acids (absorbable)
Elastase
____ (lingual, gastric) begins the digestion of lipids in the stomach
Pancreatic ____ continues this digestion in the small intestine
Breaks lipids down to fatty acids and monoglycerides (absorbable
Lipase
Total volume that enters small intestines daily ~9.3L
~2.3L comes from ingestion of food and liquids
~7.0L from various gastrointestinal secretions
Small intestine absorbs ~8.3L of the fluid
Large intestine absorbs ~0.9L of the fluid
Leaves only ~0.1L (100mL) that is excreted in feces each day
Small Intestine water absorption:
Terminal portion of the GI tract:
Large Intestine
- Completing the process of absorption
- Produces certain vitamins (vitamin K and biotin)
- Forms feces for excretion
- Excretes the solid waste products from the body
Functions of Large Intestine
Large Intestine:
Has four major regions extending from ileum to anus:
Cecum
Colon
Rectum
Anal Canal
Large Intestine:
~5 ft long, ~2.5inches in diameter
Attached to the posterior abdominal wall by the _____ (peritoneal fold)
Mesocolon
Opening from the ileum to the large intestine
Allows materials to be passed from small intestine into the large intestine
Ileocoecal Sphincter (valve)
Just inferior to the ileocecal valve
Small pouch ~2.4 inches long
Open end merges with the colon
Cecum
Attached to the cecum
~3 inches long
Appendix (vermiform appendix)
Colon is divided into 4 portions:
Ascending
Transverse
Descending
Sigmoid
Ascending Colon: Retroperitoneal
Ascends on right side of abdomen to lower border of liver
Turns abruptly to the left at the ___ ___ and continues on as the transverse colon
Hepatic Flexure
Transverse Colon:
Peritoneal
Crosses the abdomen until left side where it turns inferiorly at the ____ ____
Splenic Flexure
Descending Colon:
Retroperitoneal
Descends on left side to the level of the ___ ___
Iliac Crest
Sigmoid Colon:
Peritoneal
Begins near left iliac crest, projects medially to midline
Terminates at rectum ( ___ ___ vertebra)
~3rd sacral vertebra
The last 8 inches of the GI tract
Lies anterior to the sacrum and coccyx
Terminal 1 inch of the ____ is called the anal canal
Rectum
Mucous membrane of this canal is arranged in longitudinal folds called anal columns
Columns contain arteries and veins
Anal Canal
Brush border enzymes:
α-dextrinase
Maltase
Sucrase
Lactase
Carbohydrate digesting:
Brush border enzymes:
Aminopeptidase
Dipeptidase
Protein digesting (PEPTIDASES)
Brush border enzymes:
Phospholipase B1
Lipid digestion
____ (dentate) line- lies at the inferior most portion of the anal columns
Pectinate Line
Above this line, the upper 2/3rd of the canal is only sensitive to ___
Below this line, the lower 1/3rd of the canal is sensitive to ___, ___, ____
Upper 2/3 - Stetch
Lower 1/3 - pain, temperature, temp
Knowing Pectinate (dentate) line demarcations is important when discussing ____
Hemorrhoids
Large Intestine wall contains 4 layers:
Serosa
Muscularis
Submucosa
Mucosa
In the Serosa:
____ ____ - small pouches of visceral fat attached to the teniae coli
Omental Appendices
Large Intestine, ___ has two layers:
External layer of longitudinal smooth muscle
Internal layer of circular smooth muscle
Muscluaris
Portions of this layer are thickened, forming three bands called teniae coli
External Muscularis of Large Intestine
Teniae coli contract causing the large intestine to gather together forming ____
These give the colon it’s “puckered” or “pouched” appearance
Haustra
Large Intestine, _____ is areolar connective tissue
Submucosa
Large Intestine, Mucosa has 3 tissues:
Simple columnar epithelium
Lamina propria
Muscluaris mucoasae
Large Intestine, Mucosa-
Simple columnar epithelium:
Mostly absorptive and goblet cells (located in crypts of ____ in intestinal glands)
Lieberkuhn
Large Intestine:
Mucosa-
Lamina Propria
Solitary ___ ___ found in this layer extending to the submucosa
Lymphatic nodules
There are not ___ ___ (___) or villi in the Large intestine
Circular folds (plicae)
Mucus is secreted by cells in the colon
No ___ are secreted
Chemical digestion in colon occurs through the activity of ___
Enzymes
Bacteria
Large Intestine:
Releases hydrogen, carbon dioxide, methane gases
Leads to flatus (gas)
Releases indole, skatole, ___ ___
Gives odor to feces
Hydrogen sulfide
Bacteria also breakdown remaining ____ into stercobilin
Gives feces normal brown color
Bilirubin
Although 90% is absorbed in small intestine, ___ ___ continues to absorb water
Usually only 0.5-1.0L of water enters the large intestine daily
~900mL is absorbed
~100mL is excreted
Large Intestine
As chyme remains in large intestine (3-10 hours), it becomes a solid or semisolid due to water absorption/reabsorption
At it becomes more solid, it is no longer called chyme, it is called ___
Feces
Feces chemically contains:
- Water
- Epithelial cells
- Bacteria
- Products of bacterial decomposition
- Unabsorbed digested materials
- Indigestible parts of food
its poo
Smooth muscle is responsible for the movement of food from the lower esophagus to the rectum
Two types of movement occur:
- Peristalsis
2. Segmentation
Wavelike ripple of muscle of hollow organ
A bolus stretches the lumen walls triggering a reflex contraction of muscle that pushes the bolus forward
Each time bolus pushed forward, this cycle repeats itself in that new location
Peristalsis
A mixing movement
Digestive reflexes cause a forward and backward movement within single segment
Helps to mechanically break down food and mix with digestive juices
Segmentation
2 different types of motility:
Gastric Motility
Intestinal Motility
Gastric Motility:
Emptying the stomach takes approximately 2-6 hours after ingestion of a meal
The ___ ___ opens briefly every 20 seconds, allowing 2-3mL of chyme to pass through
Pyloric Sphincter
Gastric Motility: Hormonal Regulation-
Fats and other nutrients in the duodenum stimulate the intestinal mucosa to release ___ ___ ___ ___ into bloodstream
AKA GIP (Gastric Inhibitory Polypeptide)
When it reaches stomach via circulation, it has an inhibitory effect on gastric muscle, decreasing the peristalsis motions (this slows gastric emptying)
glucose dependent insulinotropic polypeptide (GDIP)
Gastric Motility: Nervous system regulation-
Chemoreceptors and baroreceptors stimulated in duodenal mucosa cause a reflex inhibition of gastric peristalsis known as ___ ____
This causes slowing of gastric emptying
Enterogastric Reflex
Motility where Peristalsis occurs and
Segmentation occurs
Intestinal Motility
Reflexes of GI system:
Gastroileal Reflex
Enterogastric Reflex
Gastrocolic Reflex
Defecation Reflex
Secretory and motor activity of the stomach send signals to the terminal/distal portion of the ileum early in the meal causing acceleration of movement through the ileocecal sphincter
Gastroileal Reflex
Signals from the small and large intestine distension inhibit stomach motility and secretion to allow for more time to move contents forward
Enterogastric Reflex
Signals from excessive stomach activity (late meal, completion) cause movement of feces in the colon to move forward into the rectum
If paying attention to it, many people can evacuate bowels 45-60 min after a meal
Gastrocolic Reflex
Distention of the rectum triggers baroreceptors that signal the colon and anal canal to contract
This occurs at a rectal pressure of ~18mmHg
Defecation Reflex
At ~55mmHg of anal pressure, the internal sphincter relaxes
At this time, the only thing keeping feces inside is the external anal sphincter being voluntarily contracted
Between 18-55mmHg of pressure, you can voluntarily defecate by straining
____ ____ increases abdominal pressure, mechanically pushing fecal matter forward allowing for a bowel movement
Once pressure nears 80mmHg, depending on the person, the external anal sphincter may fail, allowing feces to pass through
Valsalva
Aging and the GI system:
review slides 65 / 66 / 67!
Kupffer cells AKA
Stellate Reticuloendothelial cells
Fixed phagocytes found within sinusoids that help “clean” blood
Kupffer cells AKA Stellate Reticuloendothelial cells
Destroy worn out red and white blood cells, bacteria, and other foreign matter
Kupffer cells AKA Stellate Reticuloendothelial cells
Liver functions in carbohydrate (starch) metabolism?
glycogenolysis (in low blood plasma glucose)
OR
glycogenesis (high blood plasma glucose)
Liver functions in lipid metabolism?
synthesize and store triglycerides
synthesize certain lipoproteins
synthesizes some cholesterol
-adds some cholesterol to bil to aid in lipid metabolism
Liver functions in protein synthesis?
synthesis of transport proteins
-examples: haptoglobulin, IGF binding, sex-hormone binding, thyroxin binding, transferrin, vitamin-D binding
