Digestive System Flashcards
Where does the GI tract start and end?
Starts from the mouth to the anus
How does the digestive system maintain homeostasis?
- Breaks down food into forms that can be used by cells
- Absorbs water, minerals and vitamins
- Eliminates waste from the body
What are the 6 processes of digestion?
- Ingestion
- Secretion
- Mixing and propulsion
- Digestion
- Absorption
- Defecation
Describe the process of ingestion:
Taking food and liquid into mouth
Describe the process of secretion:
Release of water, acids, buffers and enzymes
How much secretion takes place per day?
7L/day
What factor determines the motility of the GI tract?
Mixing and propulsion
Describe the process of mixing:
Segmentation: Increases contact of food with digestive chemicals though mechanical digestion
What muscles are contracted during mixing/segmentation?
In the stomach
Circular muscles
What type of digestion is segmentation/mixing?
Mechanical digestion
Describe the process of propulsion:
Peristalsis: The movement of muscles within the GI tract that facillitates movement of food
What type of muscle is involved in peristalsis?
Longitudinal muscles
What are the two types of catabolism?
- Mechanical digestion
- Chemical digestion
Describe the process of mechanical digestion:
Teeth cut and grid food, mixing and churning of food
Describe the process of chemical digestion:
Required for the breaking down and absorption of large carbohydrate, lipid, protein and nucleic acid molecules into smaller molecules
What particles can ge absorbed without chemical digestion?
- Vitamins
- Water
- Ions
- Cholesterol
Describe the process of absorption:
Entrace of digested molecules into the blood stream and lymph
What is the cardiac antrum?
The distal part of the esophagus where the stomach meets
What takes place in the esophagus; segmentation or peristalsis?
Peristalsis
Describe the process of defecation
Elimination of wastes, undigested material, bacteria, cells sloughed off from the lining of the GI tract
What happens to the food that is not absorbed into the blood and lymph?
It goes into the liver
What are the four layers of the GI tract from deep to superficial?
- Mucosa
- Submucosa
- Muscularis
- Serosa
What is the purpose of the mucosa?
- To increase SA
- To allow expansion
What are the 3 layers of the mucosa from deep to superficial?
- Epithelium
- Lamina Propria
- Muscularis Mucosae
What is the epithelium of the muscosa in contact with?
Directly in contact with the contents of the GI tract
How often is the muscosal epithelium sloughed off and replaced?
Every 5-7 days
What structures does the lamina propria contain?
- Many blood vessels
- Many lymphatic vessels
- MALT
What does MALT stand for and what does it do in the body?
Mucosa assisiated lymphatic tissue
(Protects the body against disease)
The circular and longitudinal muscles are in the muscularis mucosae.
True or false?
FALSE
What is the function of the muscularis mucosae?
Throws the mucosa of the stomach and small intestine into small folds which increases the SA and allows for expansion
What structures are located in the submucosa?
- Blood vessels
- Lymphatic vessels
- Submucosal plexus
What is the submucosal plexus?
Extensive network of neurons
What are the layers of the muscularis?
- Inner layer
- Outer layer
What layer of the GI tract contains the myenteric plexus?
The muscularis layer
What layer of the muscularis contains the smooth muscle oriented in longitudinal fibers?
The outer layer
What layer of the muscularis contains the smooth muscle oriented in circular fibers?
Inner layer
Where is skeletal muscle found in the GI tract?
- Mouth
- Pharynx
- Upper esophagus
- External anal sphincter
Skeletal muscle is under voluntary control.
True or false?
True
What does the serosa form?
The visceral peritoneum
What layer of the GI tract does the esophagus lack?
The serosa
What is the largest serous membrane of the body?
The peritoneum
What are the layers of the peritoneum?
- Parietal peritoneum
- Visceral peritoneum
- Peritoneal cavity
- Retroperitoneal cavity
What does the parietal peritoneum line?
The wall of the abdominal cavity
The visceral peritoneum lines all of the organs of the GI tract.
True or false?
False. Lines SOME of the organs.
Doesnt line esophagus or reteroperitoneual organs
What is contained in the peritoneal cavity?
Peritoneal fluid
What does intraperitoneal mean?
Organs located within the peritoneum
What does retroparitoneal mean?
Organs located behind the peritoneum
What is the function of the peritoneal folds?
- Bind organs to one another and to abdominal wall
- Supply blood and lymphatic vessels, and nerves to the organs
What are the 5 folds of the peritoneum?
- Greater Omentum
- Lesser Omentum
- Falciform ligament
- Mesentery
- Mesocolon
What is the largest fold of the peritoneum?
The greater omentum
Describe the location of the greater omentum:
- Hangs from the greater curvature of the stomach
- Drops anterior to the small intestine
- Turns back upward and attaches to the transverse colon
The Greater omentum is a single layer.
True or false?
False. Double layered
What structure and tissue are located within the greater omentum?
- Lymph nodes located within it
- Contains significant amount of adipose tissue
Where is the lesser omentum located?
Extends between the inf. edge of the liver to the lesser curvature within the stomach
What structures are contained in the lesser omentum?
- Proper hepatic artery
- Hepatic portal vein
- Common bile duct (portal triad)
- Lymph nodes
What is the function of the falciform ligament?
Separates the right lobe of liver from the left lobe
What does the falciform ligament do?
Attaches the liver to the anterior abdominal wall and the diaphram
What organ is the only digestive organ attached to the anterior abdominal wall?
The LIVER
Does the stomach move during respiration?
why
Yes, because it is attached to the liver
What is the shape of the mesentery?
Fan shaped
What fold of the peritoneum binds the jeujunum and illum to the posterior abdominal wall?
The mesentery
What fold of the peritoneum binds the transverse colon to the posterior abdominal wall?
The mesocolon
What does the mesentery and mesocolon do together?
- Hold the intenstines loosely in place
2. Allows for movement from muscular contractions (mixes and propels contents)
What is an abnormal accumulation of fluid in the peritoneal cavity called?
Ascites
What is Ascites caused by?
- Cirrhosis of the liver
- Cancer
- Heart and kidney failure
What are the retroperitoneal structures?
- Suprarenal (adrenal) gland
- Aorta/IVC
- Duodenum (second and third part-decending and horizontal)
- Pancreas (except tail)
- Ureters
- Colon (ascending and descending)
- Kidneys
- Esophagus
- Rectum
Where does the head of the pancreas sit?
Sits in the C-shape (lesser curvature) part of the stomach
What parts of the colon is most posterior?
The ascending and descending
Where is the oral vestibule?
The spot between the cheeks and teeth
Where is the oral cavity proper?
Located between the dental arches (btwen the teeth and tounge)
Where is the fauces located?
From the oral cavity to the orpharynx
What does the laryngeopharynx branch into?
Branches into the larynx and esophageous
What is the function of the Uvula?
Prevents swallowed food from entering the nasal cavity
What is the funciton of the lingual frenulum?
Limits the movement of the tounge posteriorly
What are the 3 phases of swallowing?
- Voluntary phase
- Pharyngeal phase
- Esophageal phase
Describe what takes place during the volunary phase of swallowing:
Bolus of food is pushed by tounge against hard palate and then moves toward oropharynx
Describe what takes place during the pharyngeal phase of swallowing:
As bolus moves into orophraynx, the soft palate closes off the nasopharynx, the epiglottis closes over the laryngeal opening.
Describe what happens during the esophageal phase of swallowing:
Esophageal muscle contractions push bolus toward stomach, soft palate and epiglottis return to thier pre-swallowing positions.
How long is the esophagus?
25 cm
Is the esophagus collapsible?
Yes
Where does the esophagus start and end?
Starts at the junction with laryngeopharynx and ends at the cardiac antrum.
What structure does the esophagus pass through at T10?
Passes through the esophageal hiatus (opening in the diaphram)
What are the 2 esophageal sphincters and where are they located?
- Upper-C6
- Lower-T11
What esophageal sphinter is located at the gastroesophageal junction?
The lower esophageal sphincter
What controls the opening into the stomach?
The cardiac sphincter
Is there digestive enzymes in the esophagus?
No.
Where is the stomach generally located in relation to the MSP?
Mostly left of the MSP
What are the parts of the stomach?
- Cardia
- Fundus
- Body
- Pyloric part
What is the function of the Cardia?
Surrounds the opening of the esophagus
What is the most superior portion of the stomach under the diaphram?
The Fundus
What is the most posterior part of the stomach?
The fundus
What are the 3 parts of the pyloric part of the stomach?
- Pyloric antrum
- Pyloric canal
- Pylorus
What is the pylorus?
The opening in the duodenal wall
What forms the rugae in the stomach?
The muscularis muscoae
What is the purpose of the rugae in the stomach?
Allows for expansion of the stomach
Why do we have 3 layers of muscle in the stomach?
For mechanical digeston
Where does the majority of digestion take place?
In the small intestine
What are the 3 processes of the stomach?
- Mechanical digestion
- Chemical digestion
- Gastric emptying
What process of digestion in the stomach mixes saliva, food and gastric juices to form chyme?
Mechanical digestion
Where does propulsion take place in the stomach?
From the body of the stomach to the pylorus
Describe the process of retropulsion:
Food particles are initially to large to fit through the pylorus so they are forced back into body of stomach. This process continues to repeat and keeps mixing particles with gastric juices until particles are small enough to pass through.
How many L can the stomach hold?
1-1.5 L
During chemical digestion in the stomach, what solution is secreted into the blood? What is its function?
Gastrin-to create a chain of events that eventually produce the gastric juice.
What 4 things is the gastric juice made up of?
- HCL
- Pepsin/pepsinogen
- Intrinsic factor
- Gastric lipase
What is the function of HCL?
Kills bacteria and acivates pepsinogen into its active form;pepsin
What is the function of pepsin/pepsinogen?
Begins the digestion of protiens
What is the function of Intrinsic factor?
Aids in absorption of B12
Does the body naturally produce B12?
No, need to get it from food
What is the function of gastric lipase?
Aids in the digestion of fats
What causes the esophageal sphincter to contract, the pyloric sphincter to relax, and the motility of the stomach to increase?
Secretion of gastrin into the blood
What is gastric emptying?
Passage of chyme through the pyloric sphincter
How much chyme goes through the pyloric sphincter at a time?
3 mL at a time
What organs are located on the anterior surface of the stomach?
- Diaphram
- Anterior abdominal wall
- Left and quadrate lobes of the liver
What organs are located on the posterolateral surface of the stomach?
The spleen
What organs are located on the posterior surface of the stomach?
- Left kidney
- Pancreas
What is the smaller lobe of the liver?
Left lobe
Where is the spleen located in relation to the diaphram?
Immedietly inferior to diaphram
What are the 5 different cells located in the gastric pit of the stomach?
- Surface mucous cell
- Mucous neck cell
- Parietal cell
- Chief cell
- G cell
What is the function of the surface mucous cell in the stomach?
- Secretes mucus for protection of the lining of the stomach
What is the function of the mucous neck cell in the stomach?
- Secretes mucus for protection of the lining of the stomach
What is the function of the parietal cell in the stomach?
- Secretes hydrocloric acid (HCL)
- Secretes intrinsic factor
What is the function of the chief cells in the stomach?
- Secretes pepsinogen
- Secretes gastric lipase
What is the funciton of G cells in the stomach?
Secretes the hormone gastrin
What is the function of B12
- Erythropoiesis (RBC production)
Where do ulcers ussually appear in the stomach?
ON the duodenal bulb and lesser curveture
What does chyme entering the small intestine contain?
Partially digested carbs, protiens and lipids
How long in diameter and length is the small intestine?
2.5 cm in diameter
3 m in length
What are the 3 parts of the small intestine and how long is each part?
- Duodenum-0.25m
- Jejunum-1m
- Ileum-2m
What small structures are located all along the entire mucosal layer of the small intestine? How wide are these structures?
- Pilcae circulares-10mm
- Villi-.5-1mm
- Microvilli-1 microm
What is the purpose of the plicae circulares?
To stay permententally no matter how much the small intestine is stretched to increase the SA.
What forms the brush border?
The microvilli
At what vertebral level does the small intestine start and end at?
L1-L4
What are the 4 parts of the duodenum?
- The duodenal bulb (superior)
- Descending
- Horizontal
- Ascending
What part of the submucosa in the duodenum secretes alkaline mucus?
The duodenal glands/Brunners glands
What is the function of the jejunum?
Chemical digestion and absorption
Label ALL anatomy
Do this, and then you can be done studying for the day.
What is the suspensory muscles of the duodenum?
The Ligament of Treite
What are the 2 types of cells in the mucosal layer of the small intestine?
Excluding the cells in the intestinal glad
- Absorptive cells
- Goblet cells
What type of gland is located in the mucosa of the small intestine?
The crypts of lieberkuhn (intestinal glands)
What cells are located in the crypts of lieberkuhn glands?
- Paneth cells
- S-cells
- CCK cells
- K cells
What do paneth cells do?
Secrete lysozyme which regulates the microbial population
What type of cells are paneth cells?
Enteroendocrine cells
What do S-cells do?
They secrete secretin which stimulates the secretion of pancreatic juice and bile by causing the liver to increase its output
What do CCK cells do?
They secrete cholecystokinin which acts mostly on the gall bladder and stimulates the release of pancreatic juices
What do K-cells do?
They secrete a gastric inhibitory peptide which stimulates the release of insulin by the pancreas and slows gastric emptying
What cells contains the microvilli in the small intestine? What do these cells form?
The absorptive cells which forms the brush border
What do absorptive cells in the small intestine produce?
Brush border enzymes
What does Enterokinase do?
Activates trypsinogen into trypsin
What is the function of the goblet cells in the small intestine?
They secrete mucus
What does the crypts of lieberkuhn gland produce? How much does it produce?
Intestinal juice (1-2 L)
What does the intestinal juice in the small intestine contain?
-Water
-Mucus
(is slightly alkaline)
What are the 3 phases of digestion?
- Cephalic phase
- Gastric phase
- Intestinal phase
What is the purpose of the cephalic phase?
To prepare the mouth and the stomach for food we are about to eat
What are the stimulators of the cephalic phase?
Taste, thought, smell of food
What happens physiologically during the cephalic phase?
- Increase of saliva
- Gastric juice secreted
- G cells triggered
When does the gastric phase begin? How long does it last?
A the arrival of food in the stomach, lasts 3-4 hours
What happens physiologically during the gastric phase?
- Stomach stretches
- pH increases
- Simulation of gastric juices
- Increase of peristalsis
What does the intestinal phase control?
The rate at which the chyme is entering the small intestine
What happens physiologically during the intestinal phase prior to entering the small intestine?
- CCK, GIP and secretin secreted
- Distention of the duodenum
What happens physiologically during the intestinal phase when food enters the small intestine?
- Duodenum stretches
- pH decreases
How long is the cephalic phase?
Minutes long (short)
Go over the phases of digestion in the lecture:
Just read over them
How do we know when we will convert the cephalic into the gastric phase?
Mechanical receptors in the walls of the stomach send signals to the brain to begin digestion
Why does pH increase when food arrives?
Because the food is absorbing some of that acid and tells the stomach to stimulate parietal cells to secrete HCL
How long is the large intestine in length and diameter?
Length:1.5 m long
Diameter: 6.5 cm
What is the the muscular layer of the large intestine made of?
Longitudinal bands of muscle called taenia coli which contract to form the haustra
Are there villi in the large intestine?
No
How was this image acquired?
-Erect with a barium and air contrast
-AP or PA
What are the functions of the large intestine?
- Absorbs water
- Absorbs vitamins
- Formation of feces
- Elimination of feces
What are the problems associated with having a colon that is too long?
Too much absorption would take place, leading to impaction
Where is the cecum located in relation to the ileocecal valve?
Inferior to the level of the ileocecal valve
What structure hangs of the cecum?
The appendix
Where is the vermiform appendix located?
On the posteromedial surface of the cecum in the RLQ
Where is the oblique layer of muscle located in the stomach?
Before the circular layer
What are the different parts of the colon?
- Ascending
- Transverse
- Descending
- Sigmoid
What is the hepatic flexure/right colic flexure?
Where the ascending and transverse colon meet
What is the splenic flexure/left colic flexure?
Where the transverse and descending colon meet
How long is the rectum?
6 inches/15 cm
What parts of the colon are most anterior?
- Cecum
- Transverse colon
- Proximal part of the sigmoid colon
What structures of the colon are located posteriorly to the transverse colon?
The ascending and descending colon are most posterior to the transverse colon
What structures of the colon are located the most posterior?
- The rectum
- Recto-sigmoid colon
Where is the barium sitting in the colon in this image?
(i.e. ant, posterior, medial, lat)
In the most anterior part
How do you image the hepatic flexure?
Patient erect, LPO
How do you image the splenic flexure?
Erect RPO or LAO
Where is the splenic flexure located in relation to the hepatic flexure?
Why?
Splenic flexure is superior to the hepatic flexure because of the liver near the hepatic flexure
Does the large intestine have microvilli?
Yes, just not villi
What creates the stacked coin appearence in the abdomen?
The plicae circularis in the small intestine
What is the function of the absorptive cells in the large intestine?
Water absorption
What is the function of the goblet cells in the large intestine?
Secrete mucus
What part and how much of the tounge is in the oral cavity?
The anterior 2/3 of the body is in the oral cavity
What part and how much of the tounge is in the oropharynx?
The posterior 1/3 of the root is in the oropharynx
What movement does the lingual frenulum limit?
Posterior movement
What does the tounge attach to inferiorly?
- Hyoid
- Mandible
- Styloid processes of the temporal bone
What muscle of the tounge moves the tounge side to side, in and out, form bolus, and force food back for swallowing?
Extrinsic
What muscle of the tounge changes shape of the tounge for speech and swallowing?
Intrinsic
What is the function of the papillae on the tounge?
Taste buds, increase friction to make it easier to form a bolus
What is the function of the lingual glands?
To secrete mucus and lipase
What is the general function of lipase?
To break down fats
How much saliva is secreted per day?
1-1.5 L
What is the pH of saliva?
6.35 to 6.85
What is the first step in mechanical digestion?
Mastication
What is saliva made of?
-99.5% water
-.5 % solutes
What duct is assisiated with the parotid salivary gland?
The parotid or stensen’s duct
What duct is assosiated with the submandibular salivary gland?
Wartons duct
What duct is assosiated with the sublingual salivary gland?
Rivinus ducts
What are the 3 salivary glands?
- Parotid
- Submandibular
- Sublingual
What solutes are in saliva?
- Electrolytes
- Mucus
- Lysozyme
- Immunoglobulin A
- Salivary amylase
What electrolytes are in the saliva?
- Sodium
- Pottasium
- Cloride
- Phosphate
- Bicarbonate
What is the function of mucus in saliva?
Lubricates food mass
What is the function of lysozyme in saliva?
Kills bacteria
What is the function of IgA in saliva?
Inhibits bacteria growth
What is the function of salivary amylase in saliva?
Starts the breakdown of starch into simpler sugars
What is the largest salivary gland?
The parotid gland
Where is the parotid gland located?
-anteriorinferior to the ears
Where is the submandibular gland located?
Located medial to mandibular angle, opens lateral to the lingual frenulum
Where does the parotid gland conduct secretions into?
Into the vestibule near the upper 2nd molar
How much of saliva is produced by the submandibular gland?
60-70%
(the most out of all the salivary glands)
How much of the pancreas has an exocrine function? What percentage is responsible for the endocrine function?
Exocrine: 99%
Endocrine:1%
Where is the head of the pancreas located?
At L2/L3 and sits adjacent to the descending duodenum
Where is the body and tail of the pancreas located in relation to the stomach?
Located posterior to the stomach
What is the pancreatic juice made of?
- Water
- Pancreatic amylase
- Proteolytic enzymes
- Pancreatic lipase
- Nucleases
What does pancreatic amylase break down?
Starch
What does Proteolytic enzymes breakdown?
Protiens
Go over pancreatic ducts
Do it.
What is the difference between the endocrine and exocrine functions of the pancreas?
Exocrine: Secretes pancreatic juice into the pancreatic duct
**Endocrine: ** Secretes hormones (glucagon, insulin, somatostatin) directly into the blood stream to control blood glucose levels
What function does the acinar cells preform and how much secretions do they produce a day?
They secrete 1.2-1.5 L of pancreatic juice per day
Why is the pH of pancreatic juice alakaline?
-Buffers the acidic chyme
-Stops the action of pepsin
-Creates the proper pH for the digestive enzymes
7.1-8.2 pH
What are the 2 exocrine ducts in the pancreas?
- Pancreatic duct/duct of wirsung
- Accessory duct (duct of santorini)
What forms the hepatopancreatic duct?
The pancreatic duct joining with the common bile duct
Where is the stomach located in relation to the spleen?
More medial and anterior than the spleen
Where is the spleen located?
Posterolateral and superior, just under the diaphram
What vertebral level is the duodenum located at?
L1-L4
Label the right hepatic duct, left hepatic duct, common hepatic duct on this image
Refer to notes
WHat does the cystic duct come from?
The gallbladder
What enzyme passes through the pancreatic duct?
Tripsinogen
As the enzyme tripsinogen goes through the duodenum, what is it converted into? What activates it?
Converted into trypsin; activated by enterokinase
What enzymes does trypsinogen trigger in the pancreas?
- Chymotrypsin
- Elastase
- Carboxypeptidase
- Pancreatic lipase
- Nucleases (RN, DRN)
What cell produces pancreatic juice?
Acinar cells
Where is the liver located in the quantrants of the abdomen?
Right hypochondriac and epigastric region
What lobe of the liver is bigger?
Right lobe is larger
What is located lateral to the caudate lobe?
IVC
What is located lateral ot the quadrate lobe?
Gallbladder
How does the liver produce bile?
By emulsifying fats
What does the liver detoxify?
Waste or drugs
What does the liver convert glycogen into?
Glucose
What are the three main cells located in the liver?
- Hepatocyte
- Bile canaliculi
- Hepatic sinusoids
What is the function of the hepatocytes and bile canaliculi in the liver?
- Hepatocytes: Marjor functional cells
- Bile canaliculi: Small ducts between hepatocytes that collect bile
What are the hepatic sinusoids in the liver?
- Highly permeable capillaries between rows of hepatoxytes that recieive oxygenated and deoxygenated blood
What vessel provides the hepatic sinusoids with nutrient rich, deoxygenated blood?
The hepatic portal vein
What vessel provides the hepatic sinusoids with oxygenated blood?
The hepatic artery proper
What is the portal triad?
- Branch of hepatic artery proper
- Branch of hepatic portal vein
- common bile duct
What percentage of blood is supplied to the liver by both the hepatic artery proper and the hepatic portal vein?
Hepatic artery proper: 30%
Hepatic portal vein: 70%
Label 1-6
1=Abdominal aorta
2=IVC
3=Caudate lobe
4=Stomach
5=Left lobe of liver
6=Right lobe of liver
What is chirrhosis of the liver? What does it lead to?
End stage liver disease that leads to hematemsis (vomiting up blood) because blood is unable to go through the portal vein
What creates the common hepatic duct?
The R and L hepatic duct
What creates the common bile duct?
The common hepatic duct and the cystic duct
What is the function of the gall bladder and where is it located?
-Stores and concentrates bile
-Located on the inferior surface of the liver
What lobe of the liver is more inferior? caudate or quadrate?
Quadrate
Label the; falciform ligament, liver, common hepatic duct, cystic duct, duodenum (descending), body of pancreas and head of pancreas.
What effects occur with the presence of acidic chyme and the stretching of the duodenum?
- Secretions of CCK–>
- Stimulates pancreas to secrete enzymes–>
- Stimulates gallbladder to contract and the sphincter of Oddi to relax
What effects does secretin have on the small bowel?
Stimulates the pancreas to secrete enzymes
What is the function of GIP?
Gastric inhibitory peptide-reduces gastric motility
What 3 hormones reduce gastric motility and empying?
- GIP
- Secretin
- CCK
What is the effect of gastrin the the stomach?
Promotes the release of more HCL and pepsinogen and increases gastric motility
(stimulates cheif and parietal cells)
When is salivary amaylase secreted?
The cephalic phase
What is it called when there is air under the hemidiaphram?
Pneumoperitoneum