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148 Cards in this Set

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Describe how the testis descend in a developing embryo.
The gubernaculum guides the testis down from the posterior abdominal wall to the scrotum. The testis already have developed their connections to nerves and blood vessels before they start to descend, so these come too. The parietal peritoneum evaginates from the lower abdominal wall and forms the processus vaginalis that grows inferiorly and pushes the abdominal wall layers ahead. (This causes the transverse fascia and internal and external oblique muscles to evaginate as well.) The tranversus abdominus does NOT invaginate, though. The testis follows the gubernaculum and descends along the process vaginalis. This process forms the inguinal canal.
What is the gubernaculum?
A condensation of mesoderm that guides the testis into the correct position. It is located between the inferior portion of the testis and the skin of the presumptive scrotum.
What is the processus vaginalis?
An evagination of the parietal peritoneum that eventually becomes part of the scrotum as the testis descend.
Embryo, developing testis
Where is the transverse fascia in the developing embryo?
Exterior to the peritoneum, but interior to (and just beneath) the three layers of abdominal muscles (transversus abdominus, internal and external obliques). It will evaginate with the testis and become part of the scrotum.
Between the peritoneum and the transversus abdominus
What is the inguinal canal? How is it formed?
It is formed from the descent of the testis. It begins internally at the deep inguinal ring, where the transversalis fascia evaginates around the processus vagenalis and testis. The canal ends at the superficial inguinal ring, where the external oblique evaginates.
The inguinal canal contains the spermatic cord (nerves, vessels and ducts of the testis) in males.
How does the ovary descend? How does it differ from the descent of the testis?
The process is similar to testicular descent. A process vaginalis evaginates and the inguinal canal forms in the abdominal wall. The gubenaculum attaches to the ovary and the labium majus, but the ovary only descends into the pelvis.
The testis descend much further than the ovaries.
Final destination
What is left of the gubernaculum in adulthood?
In males, it pretty much diappears but can remain as the scrotal ligament. In the female, the gubernaculum remains are longer (b/c the ovary did not descend as far as the testis). The part from the ovary to the uterus is called the round ligament of the ovary, while the remnant from the uterus to the labium majus is the round ligament of the uterus (which traverses the inguinal canal).
Round ligaments...
The transversalis fascia, the first layer encountered by the descending processus vaginalis and testis/ovaries, forms an evagination called the ____ ____ ____.
internal spermatic fascia
The site where the transversalis fascia evaginates is the ____ ____ ____.
Deep inguinal ring.
Where is the deep inguinal ring located?
The inguinal region, idiot. It lies lateral to the interior epigastric artery and vein and above the inguinal ligament.
What is the inguinal ligament?
The inferior edge of the external abdominal oblique aponeurosis. It extends to the pubic tubercule as the lateral crus of the superficial inguinal ring.
Which structures enter the deep inguinal ring in the adult?
The ductus deferens, testicular vessels, and the round ligament of the uterus.
The internal abdominal oblique muscle gets pushed ahead of the descending processus vaginalis and testis to form the ____ ____ in the adult male.
Cremaster muscle
What is the function of the cremaster muscle?
To regulate temperature in the testis and allow for the optimal temperature for spermatogenesis. The muscle contracts to pull the scrotum closer to the body and make it warmer.
What happens as the processus vaginalis and testis descend through the external oblique?
The muscle fiber of the external oblique end more laterally to where the testis and process vaginalis descend, so the structures only go through the aponeurosis of the external abdominal oblique. The aponeurosis splits to form the superficial inguinal ring. The two bands of tissue formed by the aponeurotic tissue are called medial and lateral crura. The fascia covering the aponeurosis forms the external spermatic fascia. The inguinal ligament continues to the pubic tubercule as the lateral crus.
What exits through the superficial inguinal ring?
The spermatic cord (round ligament)
The conjoint tendon is formed from tendons of which muscle groups?
Fusion of the transversus abdominus and internal abdominal oblique muscles aponeuroses, where they attach to the pubis.
What are the types of inguinal hernias?
Direct and indirect
Define hernia.
The protrusion of an organ or part of an organ into an opening where it does not belong.
What happens during a direct hernia?
There is a weak spot at the region lateral to the conjoit tendon and medial to the inferior epigastric artery that consists of only peritoneum, transversalis fascia, and external oblique aponeurosis. Small intestine can easily push through this weak spot. Since the width of the conjoint tendon varies considerably from person to person, some people have a higher propensity to have a direct hernia than others. When the internal oblique and transversus abdominus contract, the weak area arch is reduced.
What is the inguinal triangle?
It is an area bound by the inferior epigastric vessels laterally, the lateral edge of the rectus abdominus medially, and the inguinal ligament inferiorly. This is the site of the direct inguinal hernia
What happens during an indirect inguinal hernia?
When the processus vaginalis remains patent, there is an open pathway that can extends all the way to the scrotum. The deep inguinal ring is the weak spot for this hernia, where a hernia can follow the pathway parallel to the one the descending testis took. It would remain within the tunica vaginalis, even if the hernia proceeds all the way down to the scrotum.
Because the deep inguinal ring lies lateral to the inguinal triangle and lateral to the inferior epigastric vessels, it is called an indirect inguinal hernia.
What is the tunica vanginalis?
The remaining portion of the processus vaginalis after the testis descend that exists as a celomic sac that surrounds the testis.
What is the procedure for checking for either type of inguinal hernia?
Use a finger to invaginate the scrotal or labial skin to the site of the superficial inguinal ring. Push upward and laterally. The hernia will bulge toward your finger when the patient is asked to cough.
Which hernias of the groin are more prevalent in men? In women?
Indirect inguinal hernias are more common in men. Femoral hernias are more common in women.
What two major phenomena happen to transform the gut tube of the developing embryo into the adult gut tract?
1. Elongation and differential growth in various parts of the tube
2. Series of positional changes= gut rotation
Where is the midgut loop located in the developing embryo?
It is a long loop that extends into the body stalk. This will be the forerunner of the small intestine and ascending and transverse components of the large intestine.
Name the three branches of unpaired arteries that supply the gut and which structures they support?
1. Celiac artery- foregut; stomach, portion of the duodenum, liver, gall bladder, pancreas
2. Superior mesenteric artery- midgut; duodenum, jejunum, ileum, cecum, ascending and transverse colon
3. Inferior mesenteric artery- hindgut; descending and sigmoidal colons and rectum
What happens to the ventral mesentery?
The abdominal forgut retains the ventral mesentery where the liver develops. Howevert, the ventral mesentery of the midgut and hindgut breaks down, forming a single peritoneal cavity.
Describe the rotation of the stomach.
It rotates and bends to the right. The original dorsal margin faces to the left, forming the greater curvature of the stomach. The original ventral margin faces to the right, forming the lesser curvature of the stomach.
What happens to the dorsal mesogastrium during embryo development?
The dorsal mesogastrium (which lies right behind the stomach initially) grows and bulges left and downward. It forms the greater omentum that extends over the transverse colon and loops of the small intestine.
Describe the rotation of the midgut loop.
The midgut loop rotates 270 degrees, with the superior mesenteric artery as the point of rotation. The loop initially extends into the body stalk, but as it rotates (clockwise if you are looking from the perspective of the embryo), it returns back to the peritoneal cavity.
What is a communicating vs. noncommmunicating hydrocele in the scrotum?
A communicating hydrocele means that the tunica vaginalis maintains an opening with the peritoneum. A noncommunicating hydrocele has had that canal fused off.
How does the hindgut rotate?
There is no rotation of the hindgut.
Define primarily retroperitoneal vs. secondarily retroperitoneal. Which structures are associated with each?
Primarily retroperitoneal structures developed along the posterior body wall, behind the parietal peritoneum, and NEVER had a mesentery. The kidneys are this type.
Secondarily retroperitoneal- structures that had mesenteries, but got pushed against the body wall during development and their mesenteries fused with the peritoneum and disappeared. These structures include the duodenum, pancreas, and ascending and descending colon.
What is the purpose of mesentery?
To supply the suspended organs of the body with blood vessels and nerves.
What happens to the ventral mesentery during embryo development?
Below the umbilicus, the ventral mesentery disappears. But the foregut retains the mesentery around the liver and is called ventral mesogastrium (the ventral mesentery for both the stomach and upperportion of the duodenum).
The liver grows into the ventral mesogastrium and becomes interposed between the stomach and duodenum and the attachment of the mesentary to the ventral body wall. The ventral mesentery forms two structures- the lesser omentum (connects stomach, duodenum to liver) and the falciform ligament (connects liver to vental body wall). The liver is suspended ventrally and dorsally by the ventral mesogastrium.
A direct inguinal hernia occurs ____ to the inferior epigastic artyer, while an indirect hernia occurs ____ to the same artery.
Medial, lateral. The direct inguinal hernia occurs through the inguinal triangle, while the indirect hernia occurs through the deep inguinal ring.
Name the derivatives of the ventral mesentery.
Falciform ligament= connects liver to anterior body wall; contains round ligament of the liver (formerly umbilical vein)
Lesser omentum= connects liver to stomach and duodenum; composed of hepatogastric and hepatoduodenal ligaments
Falciform, lesser omentum
What forms the greater omentum?
Dorsal mesogastrium- a potion balloons out to form the greater omentum, which hangs over the abdominal organs, starting below the greater curvature of the stomach.
Apron hanging over abdominal organs
How does the spleen interact with the dorsal mesentery?
The spleen develops within/subdivides the dorsal mesogastrium.
The gastrosplenic (lienogastric) ligament connects the stomach to the spleen.
The lienorenal ligament connects the spleen to the posterior body wall over the left kidney.
Describe what happens to the secondarily retroperitoneal structures. Which structures are they?
They are pressed against to the posterior body wall and their dorsal mesenteries fuse with the parietal peritoneum. Their mesenteries are the former mesoduodenum, the former ascending mesocolon, and the former descending mesocolon.
What is the mesentery proper?
The retention of the dorsal mesentery by the jejunum and the ileum. It connects the small intestine to the posterior body wall.
What is the transverse mesocolon?
The part of the dorsal mesentery retained by the transverse colon.
What does the dorsal mesogastrium do? What are its regions?
It connects the stomach to the dorsal body wall. The regions are: greater omentum, gastrocolic, gastrosplenic, lienophrenic, and lienorenal ligaments.
The gastrocolic ligament connects the _____________ to the __________.
Greater curvature of the stomach to the transverse colon. It is a portion of the greater omentum, which is a region of the dorsal mesogastrium.
The gastrosplenic ligament connects the ____ to the ____.
Stomach to the spleen. It is a region of the dorsal mesogastrium.
The leinorenal ligament connects the ____ to the ____________.
Spleen to the parietal peritoneum of the body wall over the kidney.
The mesentery proper connects the _____ and ______ to the ______________.
Jejunum and ileum to the parietal peritoneum of the posterior body way.
The transverse mesocolon connects the __________ to the ______________.
Transverse colon to the parietal peritoneum of the posterior body wall.
What are the two regions of the peritoneal cavity and what comprises them?
The greater and lesser omental bursa sacs. The greater sac comprises most of the peritoneal cavity and the lesser sac a small compartment located posterior to the stomach.
They communicate via the epiploic/omental foramen.
How is the greater omental bursa sac in the abdomen subdivided?
The transverse colon subdivides the greater sac into a supracolic compartment (stomach, liver, spleen) and the infracolic compartment (small intestine, ascending and descending colons).
Communication between the areas is along the paracolic gutters (depressions along the lateral borders of the ascending and descending colons).
Where are the subphrenic spaces located?
Beneath the diaphragm, above the liver, stomach and spleen.
What does the digestive system develop from?
A portion of the endodermally lines yolk sac that is incorporated into the body.
Salivary glands secrete a substance that begins _____ _____.
Carbohydrate digestion
The stomach initiates digestion of _____.
What is chyme?
The pasty substance of partially digested food that is moved from the stomach into the intestine.
What is mixed with the chyme once it is moved into the small intestine?
Alkaline secretions from the pancreas, liver and intestinal glands.
Name the four main layers of the digestive tract.
Mucosa, submucosa, muscularis externa, serosa (or fibrosa)
What does the mucosa of the digestive system consist of?
1. Epithelium- either nonkeratinized stratified squamous epithelium or simple columnar epithelium w/ goblet cells
2. Lamina propria- a layer of loose connective tissue that contains lymphatic vessels, capillaries, macrophages, leukocytes
3. Muscularis mucosae- a layer of smooth muscle
What is the submucosa of the digestive tract consist of?
Dense irregular connective tissue, with arteries and veins that supply the lamina propria of the mucosal layer.
Describe the muscularis externa of the digestive tract.
The muscularis externa has two layers- an inner circular and outer longitudinal- of smooth muscle.
What is the difference between the serosa and fibrosa outermost layers of the digestive tract?
They are found in different locations. The serosa is found where the get wall is covered by visceral peritoneum (stomach, jejunum, ileum, and sigmoid colon). The fibrosa is found where there is no visceral peritoneum (esophagus, duodenum, ascending and descending colons, rectum, anal canal).
Serosa consists of connective tissue covered by simple squamous epithelium. Fibrosa consists ONLY of connective tissue.
Name the two intrinsic nerve plexuses within the walls of the digestive tract. Describe them and their function.
Submucosal (Meissner's) plexus- lies in the submucosa
Myenteric (Auerbach's) plexus- lies between the circular and longitudinal layers of the muscularis externa.
Together, they form the enteric nervous system and are only found from esophagus to the anal canal. They control reflexes related to muscular movement and glandular secretion. They are strongly influenced by the autonomic nervous system. They are post-ganglionic parasympathetic neurons, but also receive innervation from sympathetic axons. Some enteric neurons have sensory function as well.
Describe the histology of the esophagus.
At the beginning all four layers of tissue. The mucosa is lines with nonkeratinzed stratified squamous epithelium that changes to simple columnar epithelium as the cardioesophageal junction. The lamina propria consists of loose connective tissue. The mucosa and lamina propria are folded extensively.
The muscularis mucosae is thick longitudinal smooth muscle. The submucosa is made of dense irregular connective tissue. The muscularis externa has an inner circular layer and an outer longitudinal layer. In the upper third of the esophagus, the muscularis externa is skeletal muscle, while the middle third is a mix of smooth and skeletal, and the lower third is entirely smooth.
At the end of the esophagus, the inner circular layer of muscularis externa is thickened to form a strong band of smooth muscle called the cardiac sphincter.
What is the function of the cardiac sphincter?
To prevent back flow and regurgitation from the stomach, so the gastric acids are contained and don't damage the esophagus.
What is the function of the stomach?
To store food, to digest proteins, and to secrete gastric juices. It is not meant to absorb much, but lipid soluble compounds, like ethanol and aspirin, are easily absorbed.
What are the regions of the stomach?
The fundus is dome shaped and is considered all area superior to the cardiac sphincter (upward and left of the cardiac sphincter). The cardiac region is the area around and including the cardiac sphincter. The body is caudal of the fundus and extends to the angular notch at the lower part of the lesser curve. The pyloric region extends from the angular notch to the pyloric sphincter.
What are rugae?
The folds in the lining of the stomach.
Describe the mucosal layer of the stomach.
It is simple columnar epithelium with many invaginations into the lamina propria. These are ducts of simple branched tubular glands. The luminal surface of the stomach and pits (adenomeres of gastric glands) are lined with surface mucous cells (simple columnar cells with round or oval basal nuclei that secrete mucus that protects the stomach).
Describe the gastric glands of the stomach mucosa.
The gastric glands are in the body and fundus of the stomach. Their adenomeres have a base, a long neck, and an isthmus where the simple tubular ducts join. There are five epithelial cell types in gastric glands: surface mucous cells, mucous neck cells, parietal cells, chief cells, and enteroendocrine cells.
Which types of cells are located in the neck of the gastric gland adenomeres? How can you distinguish them?
Mucous neck cells and parietal cells are located in the neck of the adenomere. The parietal cells are puffy and larger. The mucous neck cells have flattened, basal, dark nuclei, and pale staining apexes.
What is the difference between secretion types of the mucous neck cells and surface mucous cells in the gastric glands of the stomach?
The surface cells secrete a more neutral mucus, while the neck cells secrete acidic glycoproteins.
What is the function of parietal cells in stomach tissue? How do they work?
Parietal cells are responsible for secreting high concentrations of HCl as well as intrinsic factor. They are large and have clear or acidophilic cytoplasm.
They secrete hydrogen and chloride ions into the lumen that combine to form .1M HCl. The cells bring carbon dioxide into their cytoplasm, where it combines with water to make carbonic acid. This dissociates to form a hydrogen ion. Both are pumped from the cell but in opposite directions (blood and gut lumen). Chloride ions are pumped directly from the blood to the stomach lumen.
The cells contain intracellular canaliculi (invaginations in their apical surface) that are lined with microvilli that increase the surface area. The tululovesicular membrane allows the cells to store large amounts of membrane that are seen when the cells are actively secreting HCl. When the cells are inactive, the tubulovesicular membranes are internalized.
Intrinsic factor is used to protect vitamin B12 in the stomach. Vitamin B12 is necessary for erythropoiesis.
Why is HCl secreted into the stomach lumen?
To cleave pepsinogen to pepsin and to kill microorganisms in the stomach.
How can you differentiate between an active parietal cell of the gut and an inactive one that is not secreting HCl?
The inactive cells contain large reserves of plasmalemma in their cytoplasm, while in active cells, the plasmalemma is on the apical surface of the cell.
What is the function of chief cells in gastric glands of stomach tissue?
Chief cells are found at the base of the gastric glands. They are cuboidal or low columnar cells with zymogen granules in their apical cytoplasm that contain pepsinogen. They have prominent Golgi and RER.
How are proteins broken down in the gut?
Chief cells secrete pepsinogen, which is cleaved into active pepsin by HCl. Pepsin initiates the digestions of proteins. Enzymes from the pancreas that digest proteins act in the duodenum. These substances hydrolyze proteins into amino acids and oligopeptides. The final digestion is by peptidases in the glycocalyx from absorbative cells in the small intestine.
What is the function of enteroendocrine cells of gastric glands the stomach?
They are hormone secreting cells found near the base of glands. They secrete vasoactive intestinal peptide, serotonin, and gastrin. They have reverse polarity because their products are secreted into the blood. They have secretory granules, an APICAL nucleus, and modest amounts of RER and Golgi.
What is gastrin and where is it secreted?
Gastrin is produced by special enteroendocrine cells called gastrin cells (G cells). In the presence of proteins in the stomach, the G cells secrete gastrin, which stimulates parietal cells to secrete HCl.
Describe the lamina propria of the stomach.
It is very cellular with numerous fibroblasts and capillaries. They are many lymphocytes and other immune cells.
What does the submucosa of the stomach consist of?
Dense irregular CT, with larger blood vessels, lymphatics, and nerves. This layer also contains the submucosal plexus.
Describe the muscularis externa and serosa of the stomach.
The muscularis externa has three layers- inner oblique, middle circular, and outer longitudinal. (It has an EXTRA layer compared to rest of GI tract!) The myenteric plexus is located between the middle circular and outer longitudinal layers.
The serosa consists of loose CT covered by mesothelium. This tissue is referred to as the visceral peritoneum.
What makes up the pyloric sphincter?
The pyloric sphincter is an enlargement of the circular layer of the muscularis externa at the duodenal junction.
Enlargement of which muscle layer?
Which three structures make up the small intestine? What nutrients get absorbed in each?
Duodenum- carbohydrates, lipids, proteins, calcium, and iron
Jejunum- same as duodenum
Ileum- bile salts, vitamin B12, water, electrolytes
Describe the layers mucosa of the small intestine that are responsible for increasing the surface area.
Four specializations increase surface area- plicae circulares (crescent-shaped folds of the mucosa and submucosa), villi, intestinal glands (crypts between bases of villi to the muscularis mucosae), and microvilli on absorptive cells. The lamina propria (loose CT) is found in the cores of the villi.
What cell types are present in the small intestine? Where are they found?
There are 5 cells types in the simple columnar epithelium of the small intestine: enterocytes, goblet cells, Paneth cells, enteroendocrine cells, and M-cells. Absorptive and goblet cells are found in the glands AND villi, while Paneth and enteroendocrine cells are found ONLY in the glands. M-cells are found only in the ileum.
Describe the absorptive cells of the small intestine.
These cells are tall, columnar with basally located, oval nuclei. Their microvill appear as a brush border that has a very thick layer of glycocalyx. The glycocalyx contains enzymes which aid in carbohydrate and protein digestion. These cells also aid in fat absorption.
How are goblet cells situated in the small intestine tissue?
They are most numerous on the villi and they are unicellular glands that secrete mucus.
What are Paneth cells in the small intestine?
Paneth cells secrete lysozyme and are most prominent in the ileum. They contain large secretory granules that stain red with eosin.
What do enteroendocrine cells of the small intestine secrete?
Gastrin, motilin, cholecystokinin, secretin, substance P, and serotonin.
What is the function of M-cells in the small intestine epithelium? What is their structure?
M-cells trap antigens in the intestinal lumen and present them to immune cells. They have a few short microvilli and its apical surface has invaginations that contain pockets of lymphocytes and macrophages.
How is the lymphatic system of the small intesine organized?
There are many lymphocytes in the lamina propria and in aggregations called lymphatic nodules. The amount of lymphatic tissue increases from the duodenum to the ileum, where the lymphatic nodules form Peyer's patches. Peyer's patches fill the lamina propria and occupy much of the submucosa. The epithelium over each nodule is smooth and dome-shaped (no villi or crypts).
How does epithelial cell turnover in the small intestine work?
Cells proliferate in the crypts, where just above the base there is a region of high mitotic activity since it is a zone of stem and proliferating cells. The dividing cells migrate up the crypts and onto the villus, becoming absorptive and goblet cells as they go. At they top of the villus, they reach the sloughing off point, where dead cells are removed from the epithelium. The lifespan of an epithelial cells is 7 days.
Describe the underlying tissues of the villi in the small intestine.
The lamina propria forms the core each villus and surrounds the crypts. A lacteal, a blind lymphatic capillary, runs through the center of each villus and elongated strands of smooth muscle (derived from the muscularis mucosae) surround each lacteal. The smooth muscle shortens and lengthens the villi, so that they squeeze the lacteals and force their chylomicrons into the lymphatic vessels in the submucosa. The smooth muscle is the principle of villus motility.
What is the submucosa of the small intestine like?
In the duodenum, the submucosa contains large mucous glands called Brunner's glands with ducts that open into crypts. They secrete alkaline mucus that neutralizes the stomach's contents. This tissue also contains the submucosal plexus and it is found throughout the small intestine.
Describe the muscularis externa of the small intestine.
The muscularis externa has two layers- an inner circular layer and outer longitudinal layer. Both are made of smooth muscle. The myenteric plexus is located between the two layers.
Does the serosa or fibrosa cover the small intestine?
Both. The duodenum is covered with fibrosa, since it is not covered by visceral peritoneum. The jejunum and ileum are covered by serosa.
Name the distinguishing features of each of the parts of the small intestine. (i.e. duodenum, etc.)
Duodenum- Brunner's glands
Jejunum- plicae circulares
Ileum- Peyer's patches
Describe the mucosal layer of the large intestine.
This tissue does NOT have a large surface area like the small intestine. There are intestinal crypts, but that is it. There are absorptive cells, goblet cells, enteroendocrine cells, and a few Paneth cells. There are more goblet cells in the distal portions of the digestive tract, as the feces become more solid.
What is the role of the large intestine?
To absorb water and electrolytes.
What is the submucosa of the large intestine like?
It is similar to the small intestine- with large mucous glands. The exception is in the appendix, where there are many large lymphatic nodules that occupy the entire submucosa (some extending even further).
How does the muscularis externa vary along the large intestine?
It is modified in ascending, transverse, and descending colons where it is gathered into three thick bands called taeniae coli. (The outer longitudinal layer is not continuous around the circumference.)
At the rectum, the layer is more continuous. At the anus, the inner circular layer is thickened, forming the internal anal sphincter, while the outer longitudinal layer continues over it to form the connective tissue insertion.
How do the internal and external anal sphincters differ?
The internal is composed of smooth muscle, while the external is composed of skeletal muscle.
Which layers of the large intestine are covered by serosa and which are covered by fibrosa?
The transverse and sigmoidal colons are covered by serosa. The ascending and descending colons, rectum and anal canals are covered by fibrosa.
Name the three main branches of unpaired arteries that supply the GI tract.
Celiac artery supplies the foregut, the superior mesenteric artery supplies the midgut, and the inferior mesenteric artery supplies the hindgut. All of these systems anastamose.
Name the three main branches of the celiac artery trunk.
Common hepatic artery, left gastric artery, splenic artery.
What does the common hepatic artery branch into? Where do these branches lead?
Proper hepatic, gastroduodenal, splenic
What does the proper hepatic artery supply? What does the proper hepatic branch into?
The liver. A branch of the proper hepatic called the right gastric artery supplies the lesser curvature of the stomach
What does the gastroduodenal artery supply?
The stomach and pancreas. The gastroduodenal artery branches into the right gastroepiploic artery, which supplies the greater curvature of the stomach closer to the pyloric sphincter. The other branch of the gastroduodenal artery is the superior pancreaticoduodenal artery (a small part of which branches from the right gastroepiploic artery).
Describe the branches of the splenic artery and what they supply.
The splenic artery travels along the superior surface of the pancreas to reach the spleen via the lienorenal ligament. The splenic artery gives off the left gastroepiploic artery to supply the greater curvature of the stomach. In the lienorenal ligament, the splenic artery gives off short gastric branches to the fundus of the stomach. As it travels along the superior aspect of the pancreas, it also gives off arteries to the body and tail of that organ (pancreatic branches).
What are the four main branches of the superior mesenteric artery to the right side of the abdomen?
1. A stem that divides into anterior and posterior inferior pancreaticoduodenal arteries
2. Middle colic artery
3. Right colic artery
4. Ileocolic artery
Where does the superior mesenteric artery branch?
It passes posterior to the pancreas to enter the root of the mesentery.
What does the inferor pancreaticoduodenal arteries supply?
The pancreas and duodenum. They anastamose with the superior arteries to the same organs that come from the gastroduodenal artery.
What does the middle colic artery supply?
The transverse colon
What does the right colic artery supply?
The ascending colon
What does the ileocolic artery supply?
The ileocolic junction (ileum and cecum), where it supplies the ileum, cecum, first part of the ascending colon, and the appendix.
What is the marginal artery and how is it formed?
Interconnections among the vessels of the ileocolic artery forms the marginal artery, which is an anastamoses between the inferior and superior mesenteric arteries.
What do the arteries that arise from the left side of the superior mesenteric artery do?
They travel through the mesentery proper to the small intestine. There, they form arcades (multiple interconnections making multiple routes for blood), which branch into straight arteries (vasa recta) that go into the intestine. These are end arteries and if there is an occlusion in any of them, there will be necrosis in that portion of the intestine.
What are the three main branches of the inferior mesenteric artery?
Left colic artery, sigmoidal arteries, and superior rectal artery.
Which arteries form the marginal artery?
The ileocolic, right colic, middle colic, and left colic.
What does the left colic artery supply?
The descending colon
What do the sigmoidal branches of the inferior mesenteric artery supply?
The sigmoid colon
What does the superior rectal artery supply?
The major blood supply of the rectum
Name the two major veins that drain the abdominopelvic cavity.
Inferior vena cava and hepatic portal vein.
What is a portal system? Name the two that exist in the body.
A route in which the blood flows through two separate capillary beds before returning to the heart. The two main portal systems are the hepatic portal system and the hypophyseal portal system.
Which veins unite to form the hepatic portal vein? Where does this blood go?
Splenic, superior mesenteric, and inferior mesenteric veins. The left gastric vein drains directly into the hepatic portal vein as well. The hepatic portal vein carried blood to the second capillary bed within the liver. It drains all portions of the digestive tract that are responsible for absorbing nutrients.
Where do the spleen and pancreas drain? What significance does this have?
The hepatic portal system and into the liver. The liver receives bilirubin from the spleen (after it breaks down RBCs) and it is the first organ to receive endocrine products of the pancreas (which is important for carbohydrate metabolism in the liver).
Describe the blood flow to and through the liver.
Nutrient rich, oxygen poor blood drains to the sinosoidal beds of the liver from the hepatic portal system. This blood mixes with oxygen rich blood from the hepatic artery. The mixed blood empties through the hepatic veins and into the inferior vena cava.
Name a few of the things that can cause narrowing of the hepatic vessels and the problems that result.
Congential stenosis of the portal vein, thrombosis, hepatitis, cirrhosis of the liver. All these cause portal hypertension, which can cause blood to be shunted from the portal system through collateral pathways into the systemic system (venae cavae).
What are portosystemic anastomoses?
Connections between the hepatic portal vein and the caval system of veins. This allows for collateral circulation of the blood returning to the heart from the lower half of the body.
What are the three major pathways in the portosystemic anastomoses?
1. Superior rectal vein can drain through the middle and inferior rectal veins into the internal iliac veins
2. Left gastric vein can drain through the esophageal veins into the azygos system.
3. Paraumbilical veins (tributaries of the left portal) can drain into the superficial epigastric system at the level of the umbilicus
What are esophageal varices?
Enlarged veins caused by increased blood flow in the mucosa. These can be torn or damaged and can cause extensive internal bleeding.
What is the caput medusae?
A cluster of vessels that radiate from the umbilicus caused by the dilation of the superficial epigastric system from portal hypertension.
What are the minor anastamoses between the portal and caval system?
Where retroperitoneal veins connect parts of the azygos system or with capsular veins of the kidney, the inferior phrenics, and lumbar veins.
Describe the development of the pancreas.
The pancreas is formed from two buds from the dorsal and ventral endoderm of the duodenum. (The dorsal bud grows into the dorsal mesentery and the ventral bud grows into the ventral mesentery.) Gut rotation of the stomach and duodenum results in the dorsal migration of the ventral pancreatic bud so that it comes to lie adjacent to the larger dorsal bud. The primordia fuse to form a single pancreas. (The ventral bud forms the head and the dorsal bud forms the neck, body and tail.) The duct systems also fuse.
How is the pancreas supplied with blood?
The head is supplied by pancreaticoduodenal arteries (from the celiac and superior mesenteric arteries). The neck, body, and tail are supplied by branches from the splenic artery. The pancreatic branches form arcades within the gland that anastamose with other arteries around the pancreas.
How are the chief pancreatic duct and common bile duct related?
They join as they enter the major duodenal papilla.
What causes acute hemorrhagic pancreatitis?
If the chief pancreatic duct and common bile duct fuse and are occluded by a gallstone, the bile can reflux and enter the pancreas. There, it activates pancreatic enzymes and causes a breakdown of the pancreas.
What is the basic histology of the pancreas?
It is a mixed endocrine and exocrine gland. Enzymes are synthesized by exocrine cells. Clusters of endocrine cells called Islets of Langerhans synthesize hormones.
Describe the histology of the exocrine portion of the pancreas.
It is a compound acinar gland, where the acini are lined with pyramidal cells. Each acinar cell rests on a basement membranes and has a spherical nucleus near the base, well-developed Golgi and RER, and apical cytoplasm filled with zymogen granules. Near the lumen, acinar cells are interconnected by junctional complexes. The zymogen granules are membrane bound and released by regulated exocytosis. The granules contain enzymes and proenzymes that digest carbohydrates, proteins, fats, and nucleic acids).
What digestive enzymes are secreted by the pancreas? What do they digest?
Protein digestion- trypsinogen (secreted into duodenum, converted to trypsin by enterokinase in the glycocalyx of enterocytes), procarboxypeptidase (converted to carboxypeptidase by trypsin)
Carbohydrate digestion- amylase
Lipid digestion- bile salts (gall bladder) emulsify lipids, lipase digests lipids
Nucleic acid digestion- deoxyribonuclease and ribonuclease
What happens to nutrients once they have been digested in the intestine?
The enterocytes absorb nutrients and transfer them to the lamina propria. Amino acids, monosaccharides, and nuclei acids enter blood capillaries. Fatty acids and glycerol enter lacteals.
Describe the histological structure of the pancreatic duct.
The proximal portion of the duct begins inside the acinus. There may be one or more pale-staining centroacinar cells visible in the center of the acinus.
What is the defining feature of the pancreas histologically?
Centroacinar cells- pale staining cells visible at the center of the acinus that look slightly flat. They lie within the lumen of the duct.
What is the difference between intralobular(intercalated) ducts and interlobular ducts within the pancreas?
Intralobular ducts- intercalated among acini (within lobules); lined with simple squamous or simple cuboidal epithelium; secrete thin, watery fluid containing sodium and bicarbonate; these drain into larger interlobular ducts
Interlobular ducts- found within the connective tissue septa that divide the gland into lobules; large ducts lined with simple columnar epithelium with goblet cells that drain into the main pancreatic duct and the accessory pancreatic duct
Which two main hormones control pancreatic secretion? What do they do? What produces them?
Cholecystokinin (CCK)- stimulates secretion of a small amount of fluid rich in pacreatic enzymes, therefore promotes secretion by acinar cells; causes gall bladder to contract and deliver bile to the duodenum
Secretin- promotes secretion of an abundant fluid with lots of bicarbonate (and little enzyme) that acts on the intercalated duct cells
Both are produced by the cells of the duodenal mucosa.
What cells of the pancreas are endocrine cells? Describe their histology.
Islets of Langerhans are collections of endocrine cells that differentially stain in pancreatic tissue. The groups of cells are embedded among acini and have fenestrated capillaries connecting them. There are three cell types that can be seen with a special stain: B/beta cells, A/alpha cells, and D/delta cell.