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Histology
Digestive System Development 1
| Question | Answer |
|---|---|
| As the embryo grows, it folds ___________. As it folds this way, it also folds___________. | Cephalocaudally, Laterally. |
| As a result of cephalocaudal folding, a portion of the endodermic lined yolk sac becomes incorporated into te embryo, forming the? | Primitive gut |
| The primitive gut forms a blind ending pouch that extends from _____________ to____________. | buccopharyngeal membrane to the cloacal membrance |
| What are the four divisions of the gut tube, and where are they associated with? | 1. Pharyngeal gut, or pharynx Extends from the buccopharyngeal membrane to the tracheobronchial diverticulum. 2.Foregut -Caudal to the pharynx, extends to the liver bud. 3.Midgut -Caudal to the liver bud, extends to a point between the right 2/3 |
| What embryonic tissue forms the lining of the digestive tract? | Endoderm |
| What e. tissue forms the hepatocytes of the liver and endocrine cells of the pancreas? | endoderm |
| The stroma (CT) of glands is derived from what e. tissue? | Splanchnic mesoderm |
| Muscle, connective tissue, and peritoneal components of the gut wall are derived from what e. tissue? | Splanchnic mesoderm |
| Specifies the esophagus and stomach | SOX2 |
| Specifies the duodenum | PDX1 |
| Specifies the remaining small intestine | CDXC |
| Specifies the large intestine and rectum | CDXA |
| The endoderm-mesoderm interaction is initiated by what gene? A. Where is it expressed? B | Sonic Hedgehog, Expression throughout the gut tube. |
| As the embryo grows, it folds _______ and ______ | Cephalocaudally and laterally |
| As a result of cephalocaudal folding, part of the endoderm lined yolk sac becomes incorporated into the embryo,forming the? | Primitive gut |
| The primitive gut forms a blind pouch that extends from the _________ to the _____. | Bucscopharyngeal membrane to the cloacal membrane |
| What are the four sections of the gut tube and where are they located? | 1. Pharyngeal gut or pharynx -extends from buccopharyngeal membrane to the tracheobronchial diverticulum 2.Foregut -Caudal to the pharynx, extends to the liver bud. 3.Midgut -Caudal to the liver bud, extends to a point between the right 2/3 and t |
| What e. tissue forms the epithelial lining of the digestive tract? | endoderm |
| what e. tissue forms hepatocytes and endocrine cells of the pancreas? | endoderm |
| the stroma (connective tissue) of the glands is derived from what e. tissue? | Splanchnic mesoderm |
| Muscle, CT, and peritoneal components of the gut wall are also derived from what e. tissue? | Splanchnic mesoderm |
| Specifies the esophagus and stomach? | SOX2 |
| Specifies the duodenum? | PDX1 |
| Specifies the remaining small intestine | CDXC |
| Specifies the large intestine and rectum | CDXA |
| The endoderm-mesoderm interaction is initiated by what gene? This gene is expressed where? | Sonic Hedgehog; expression throughout the gut tube. |
| What does Sonic Hedgehog do? | Upregulates factors in the mesoderm that then determine the type of structure that forms, such as the stomach, duodenum, etc. |
| Cells of the SOMATIC MESODERM that line the intraembryonic cavity become? | Mesothelium |
| mesothelium forms the __________layer of the serous membranes that line the outside of the peritoneal, pleural, and pericardial cavities | Parietal layer |
| What e. tissue forms the visceral layer of the serous membranes covering the abdominal organs,, lungs, and heart. | Splanchnic mesoderm |
| What are mesenteries?> | Double layers of peritoneum that provide a pathway for blood vessels, nerves, and lymphatics to the organs. |
| What are organs suspended by mesenteries referred to as? | Intraperitoneal |
| organs that lie against the posterior body wall and are covered by peritoneum on their anterior surface are called what? | Retroperitoneal |
| What are peritoneal ligaments? | Double layers of peritoneum that pass from one organ to another or,from an organ to the body wall. |
| When does the respiratory diverticulum (lung bud) appear at the border with the pharyngeal gut? | 4 weeks |
| when the foregut divides into a ventral portion, the respiratory primordium, and a dorsal portion, called the? | ESOPHAGUS |
| What is the muscular coat of the esophagus derived from? | Splanchnic mesoderm |
| The upper 2/3 of the esophagus contains both skeletal and smooth muscle and is innervated by? | Vagus nerve |
| The lower 1/3 contains only smooth muscle and is innervated by the? | Splanchnic plexus |
| The stomach appears as a fusiform dilation of the foregut in the ____week of development | 4th week. |
| How does the stomach rotate in development, and what does this cause? | 90 degrees around a longitudinal axis, the left side to face anteriorly and the right side to face posteriorly. |
| The original side of the stomach grows faster, to become the? | Greater curvature. |
| The anterior side of the stomach becomes the? | Lesser curvature |
| What structures form the duodenum? | the terminal part of the foregut and the cephalic part of the midgut |
| During the ________ (time period) the lumen of the duodenum is obliterated by the proliferation of cells in its walls. What happens shortly after to the lumen? | 2nd month, it recanalizes |
| Where does the duodenum receive its blood supply from? | the celiac trunk (from foregut)and the superior mesenteric artery (from midgut) |
| The liver primordium appears in the middle of the third week, as an ________________________- of the distal end of the foregut | outgrowth of the endodermal epithelium The outgrowth is called the HEPATIC DIVERTICULUM, or LIVER BUD |
| What does the liver bud consist of? | Rapidly proliferating cells that penetrate the septum transversum. |
| What is the septum transversum? | a mesodermal plate that is found between the pericardial cavity and the yolk sac. |
| The septum transversum also helps form part of the...? | Diaphragm |
| The ventral outgrowth of the bile duct becomes? | the gallbladder and the cystic duct. |
| Epithelial liver cords mingle with vitelline veins and umbilical veins, forming the ? | Hepatic sinusoids. |
| What do the liver cords differentiate into? | liver parenchyma, lining of the bile duct |
| Mesoderm of the septum transversum divides into? | Hematopoetic stem cells, Kupffer cells, and CT |
| During what week is the liver 10% of the body weight? | 10th |
| Large clusters of proliferating hematopoetic stem cells lie between the hepatic cells and the vessel walls, which produces? | Red and white blood cells |
| When do the hepatic cells begin to form bile? | 12th week |
| The action of inhibitors in the regulation of liver induction are blocked in the prospective hepatic region by? | FGF2, secreted by cardiac mesoderm. |
| Other factors that participate in the induction of the liver formation are? | BMP's produced by the septum transversum |
| What is the action of BMP's? | Seem to enhance the competence of prospective liver endoderm to respond to FGF2 |
| Cells in the liver field differentiate into both hepatocytes and biliary cell lineages, a process at least partially controlled by | hepatocyte nuclear transcription factors HNF3 and HNF4 |
| What forms the pancreas? | Two buds from the endodermal lining of the duodenum, the dorsal pancreatic bud and the ventral pancreatic bud. |
| What does the main pancreatic duct (the duct of Wirsung) develop from? | The distal dorsal pancreatic duct and all of the ventral duct. |
| What happens to the proximal portion of the dorsal pancreatic duct? | it's either obliterated of persists as an accessory duct. (duct of Santorini) |
| Where are FGF2 and activin produced? What do they do? | notochord and endothelium of the dorsal aorta -repress sonic hedgehog expression in gut endoderm destined to form the dorsal pancreatic bud. |
| What is the ventral bud of the pancreas induced by? | Splanchnic mesoderm |
| What gene is the master for pancreas development? | PDX gene |
| What is the function of PAX4 and PAX6? | They specify the endocrine cell lineage of the pancreas. |
| Cells expressing both PAX 4 and PAX6 become? | Beta cells (secrete insulin) Delta Cells (Secrete somatostatin) and Gamma cells (secrete pancreatic polypeptide) |
| What do cells only expressing PAX6 become? | Alpha cells (secrete glucagon) |
Created by:
shuckybean