digestive system Flashcards
What are the seven organs of the GI tract?
- mouth
- pharynx
- esophagus
- stomach
- small intestine
- large intestine
- anus
What are the accessory organs of the digestive system? 6
- teeth
- tongue
- salivary glands
- gallbladder
- liver
- pancreas
Where are most digestive organs
In the abdominopelvic cavity
What are the 9 abdominal regions
- 3 superior
- 3 middle
- 3 inferior
What are the 3 superior abdominal regions
right and left hypochondriac, central epigastric
What are the 3 middle abdominal regions
right and left lumbar regions, central umbilical region
What are the 3 inferior abdominal regions
right and left iliac regions, central hypogastric
What is peristalsis?
- Wave of muscular contraction occurs throughout the GI tract (similar to pushing toothpaste through tube)
- Adjacent segments alternatively contract and relax
What is segmentation?
- Back-and-forth churning that occurs mainly in the small intestine
- Non-adjacent segments alternatively contract and relax
What is visceral peritoneum?
Covers the external surfaces of most digestive organs
What is the parietal peritoneum
lines the body wall and is continuous with the visceral peritoneum
What is the peritoneal cavity
It is between the visceral and parietal peritoneum, contains fluid to reduce friction
What is the mesenteries
- a double layer (folds) of peritoneum that extends from body wall to the digestive organs
- Holds organ in place, stores fat, route for vessels
What are the 3 parts of the ventral mesentaries?
Falciform ligament - liver to anterior abdomen wall and diaphragm
Greater omentum - greater curvature of stomach to posterior abdominal wall
Lesser omentum - liver to the lesser curvature of the stomach
What are the 4 parts of the dorsal mesentaries
Greater omentum - greater curvature of stomach to posterior abdominal wall
Mesentary - supports coils of jejunum and ilium
Transverse mesocolon - transverse colon to posterior abdominal wall
Sigmoid mesocolon - sigmoid colon to posterior pelvis wall
What organs are classified as intraperitoneal organs?
Organs that are suspended into the peritoneal cavity CONTAIN mesenteries and are movable
What organs are classified as retroperitoneal?
Organs that are NOT suspended into the peritoneal cavity LACK messentries and are immobile
What are examples of retroperitoneal organs?
pancreas, kidneys, duodenum, ascending and descending colon of LI
What are the four layers of the alimentary canal wall?
- the mucosa
- the submucosa
- the muscularis externa
- the serosa
What is the mucosa
Innermost layer of the alimentary canal wall
- consists of epithelium,lamina propria, muscularis mucosae
What is the submucosa?
external to the mucosa, contains bllod lymphatic vesseels, nerve fibres
What is the muscularis externa
external to the submucosa
Two layers: sircular muscularis - inner layer and logitudinal muscularis - outer layer
What is the serosa
the outermost layer of the alimentary canal wall
What is the oral cavity?
- entrance way for food
- lined with thick stratified squamous epithelium
What are five main features of the oral cavity?
- oral vestibule: space between teeth and lips
- oral cavity proper
- hard and soft palate: form roof of mouth
- palatoglossal arch: anchors tongue to soft palate
- Palatopharyngeal arch: anchors tongue to oropharynx
What are three main functions of the tongue
- assistance in chewing
- touch, temperature and taste
- secretion of mucins and the enzyme lingual lipase that aids in breaking down triglycerides
What are the 3 types of projections of mucosa of the tongue
- filiform - roughen
- fungiform and vallate papillae - tastebuds
What are the tonsils?
- patches of lymphatic tissue found at the entrance of the pharynx
- protection against ingested and inhaled pathogens
What are the pharyngeal tonsils?
are in the posterior wall of the nasopharynx
What are the palatine tonsils?
Are in the posterolateral region of the oral cavity
What are the lingual tonsils
Are along the posterior one-third of the tongue
What are the functions of the salivary glands?
- lubricate the oral cavity and moisten food
- dissolve chemicals that stimulate the tastebuds
- anti-microbial substances
- parasympathetic innervation simulates salivary gland secretion
What are the four jaw opening muscles?
- lateral pterygoid
- digastric
- mylohyoid
- gemiohyoid
What are the three jaw closing muscles
- temporalis
- masseter
- medial pterygoid
What does the lower esophageal or cardiac sphincter do?
- closes lumen to prevent stomach acid from entering the esophagus
Where is the upper esophageal sphincter
between the esophagus and larynx
What are the four main functions of the stomach?
- storage of digested food
- mechanical breakdown of ingested food
- chemical digestion via acids and enzymes (primarily protein digestion)
- ingested food, now called chyme (viscous, acidic, soupy mixture)
What are the 4 important regions of the stomach
- cardia
- fundus
- body
- pyloric
What are the three sections of the small intestines?
duodenum
jejunum
ileum
Where does the small intestine start and end?
Begins at PLYORIC SPHINCTER and ends at the ILEOCECAL VALVE
How can the small intestine be innervated?
Parasympathetic fibers from vagus nerve; sympathetic from thoracic splanchnic nerves
What kind of organ is the Duodenum, where does it originate, how does it connect to the liver and whats it covered with?
- Retroperitoneal apart from from the most proximal part which is intreperitoneal
- originates from pyloric sphincter
- connects to the liver by the lesser omentum
- covered by a lining of mucous membrane which protects epithelium from acid chyme
What are the three types of duodenum secretions?
- bile and pancreatic enzymes travel to the duodenum via the main pancreatic duct a bile duct
- sphincters control entry of bile and pancreatic juices
- enter the eall of the duodenum at the hepatopancreatic ampulla which opens into the major duodenal papilla
Where does the jejunum begin and what kind of organ is it?
What does it digest
Begins at the duodeno-jejunal junction
Intreperitoneal suspended by the mesentry proper
Digests and absorbs carbohydrates, proteins and fats
What does the ileum absorb and what kind of organ is it?
Absorbs vitamin B12; salts and all products of digestion that were not absorbed by the jejunum
- intraperitoneal suspended by the mesentry proper
Where does the illeum end and what does the structure do?
The illium ends at the ileocecal valve, which controls the flow of materials from the ileum into the cecum of the large intestine
What are the circular folds of the small intestine and what do they do?
PLICAE CIRCULARES
- transverse ridges of mucosa and submucosa
- increase surface area for absorption and to slow the passage of food
What are the projections along the small intestine called and what are they covered with?
Intestinal villi covered by simple columnar epithelium of enterocytes, which absorb digested nutrients
What are the microvilli and what do they do?
- finger like projections of plasma membrane on apical surface of columnar epithelial cells
- increase surface area for absorption and chemical digestion
What are the five divisions of the large intestine?
Cecum appendix colon rectum anal canal
What four colons does the large intestine form?
ascending, transverse, descending and sigmoid
The cecum
- receives chyme from the ileum
- sphincter prevents feces from travelliing back into illeum
- mostly intraperitoneal
The appendix
- blind tube that opens into posterio-medial wall of cecum
- contains lymph nodes, neutralises pathogens
- intraperitoneal
Ascending colon
- originates from cecum
- retroperitoneal
Transverse colon
Origin: hepatic flexure
- intraperitoneal
Descending colon
Origin: splenic flexure
- retroperitoneal
Sigmoid colon
Origin: sigmoid flexure
- intraperitoneal
Rectum
- retroperitoneal muscular tube
- stores feces prior to defacation
Anal canal
- approx. 3 cm long
- lines with stratified squamous epithelium
- internal and external anal sphincter regulate movement of feces
What are the three special features of large intestine
- Teniae coli - thickening of longitudinal muscularis, 3 longitudinal strips
- Haustra - puckering created by teniae coli
- Epiploic appendages - fat-filled pouches of visceral peritoneum
What are the three arteries going to the GI tract?
celiac trunk, superior and inferior mesenteric arteries
What organs does the celiac trunk supply?
Organs located above transverse mesocolon
What organs do the superior mesenteric artery supply?
Organs located on the right side of the mesentery
- ascending and transverse colon
- small intestine
- inferior parts of pancreas and duodenum
What organs do the inferior mesenteric artery supply?
Organs on the left side of the mesentry
- descending and sigmoid colon
- upper parts of rectum
What is the celiac trunk and where does it supply?
The celiac trunk (artery) is a branch of the abdominal aorta and supplies all organs (liver, stomach, spleen) which are located intraperitoneally and the transverse mesocolon
- Supplies superior parts of the pancreas and duodenumm
What are the four accessory organs of the digestive system?
- salivary glands
- liver
- gall bladder
- pancreas
What does cholecystokinin (CCK) trigger?
Release of bile and pancreatic enzymes
What is the liver covered with?
- it is covered by connective tissue capsule and visceral peritoneum (NOT the bare area)
What is the overall function of the liver?
To remove and add compounds to the blood as it circulates through the lobule
What secretion does the liver do?
- secretes plasma proteins and bile
- water and ions dilute and buffer the acids inthe chyme as it enters the SI
- aids in fat digestion
What are the two blood supplies the liver receives?
- the “hepatic portal vein” contains nutrient rich, oxygen poor blood
- The “hepatic artery proper” contains oxygen rich blood
What is the hepatic portal system?
A network of veins that carries blood from the GI tract to the liver
Where does the hepatic portal system carry blood?
carries venous blood from the GI tract and spleen to the liver before it returns to the inferior vena cava and heart:
- capillaries of GI organs
- hepatic portal veins
- sinusoids of liver (storage/metabolic conversion/excretion)
What are the three veins which drain into the hepatic portal vein?
- splenic vein
- inferior mesenteric vein
- superior mesenteric vein
What is the divide for blood supply in the liver?
- portal veins contributes 75%
- hepatic artery contributes 25%
Where dose blood from the portal veins and heptaic artery mix?
Through a liver lobule
What are the two anterior lobes of the liver called?
Right (large) lobe and left love
What is the liver ligament connecting it to the diphragm
- coronary ligament
What is the ligament between the two lobes of the liver and what does it do?
The falciform ligament
- peritoneal fold that secures the liver to the abdominal wall
What is the ligament inferior to the falciform ligament in the liver and what does it do?
Round ligament
- remnant of the fetal umbilical cord
What are the four lobes on the posterior side of the liver and where are they situated
Right lobe (largest) left lobe Caudate lobe (on top of right lobe) Quadrate lobe (inferior to caudate lobe, between L and R)
What is the part of the liver where all the blood vessels enter and exit?
Porta hepatis
What is the ligament posterior to the left lobe, seen on the superior surface?
Left triangular ligament
What structure spans between the liver and the lesser curvature of the stomach?
the lesser omentum
What does the lesser omentum contain?
the veins/arteries of the liver and stomach as well as the bile duct
What are the three parts of the gallbladder? starting inferiorly
Fundus -> body -> neck
What does bile do?
emulsifies fat
What does the cystic duct do?
connects the gallbladder to the common bile duct
What is the endocrine functions of the pancreas
AKA islet of langerhans
- produces hormones (insulin and glucagon)
- is ductless and delivers the hormones directly into blood stream
What are the exocrine functions of the pancreas?
- produces enzymes to break down fat, proteins and carbohydrates
- delivers its productinto the duodenal lumen via its pancreatic duct
What is the pathway of pancreatic enzymes?
The main pancreatic duct delivers pancreatic juice, which drains into the duodenum
