GI Anatomy BMS 200 Week 2

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Questions and Answers

How does embryonic folding contribute to the development of the gut?

Embryonic folding transforms the flat embryonic disc into a cylindrical shape, allowing for the elongation and formation of the primitive gut tube.

What role does the septum transversum play in the formation of the ventral mesentery and diaphragm?

The septum transversum serves as a central dividing structure that aids in the development of the ventral mesentery and contributes to the diaphragm's formation.

Describe the relationship between the respiratory tract and the digestive organs.

The respiratory tract and digestive organs arise from the foregut, sharing a common embryological origin before differentiating into distinct systems.

Identify the components of the GI tract and their arterial supply.

The GI tract consists of the esophagus, stomach, small intestine, large intestine, rectum, and anal canal, supplied by arteries such as the celiac trunk, superior mesenteric artery, and inferior mesenteric artery. Signup and view all the answers

What is the embryological origin of the wall of the gut?

The wall of the gut is derived from the splanchnopleure, which consists of splanchnic mesoderm and underlying endoderm. Signup and view all the answers

How does the intraembryonic coelom divide the lateral mesoderm?

The intraembryonic coelom divides the lateral mesoderm into somatic (parietal) and splanchnic (visceral) layers. Signup and view all the answers

Which structure does NOT derive from the intraembryonic coelom?

The intrathecal cavity does not arise from the intraembryonic coelom. Signup and view all the answers

What transforms the flat embryonic disc into a cylindrical structure during development?

Embryonic folding, which involves lateral and cephalocaudal folds, transforms the flat disc into a cylindrical structure. Signup and view all the answers

What is the primordium of the cecum and appendix called?

The primordium of the cecum and appendix is called the cecal diverticulum. Signup and view all the answers

What condition is characterized by the persistence of physiological herniation into the umbilical cord?

Congenital omphalocele. Signup and view all the answers

What causes gastroschisis?

Gastroschisis is caused by incomplete closure of the lateral abdominal wall during the 4th week of development. Signup and view all the answers

What is Meckel's diverticulum and what can it cause?

Meckel's diverticulum is the remnant of the yolk stalk and can cause symptoms mimicking appendicitis due to inflammation. Signup and view all the answers

What happens to the vitelline duct if it remains patent?

If the vitelline duct remains patent, it forms a direct communication called an umbilical fistula between the umbilicus and the intestinal tract. Signup and view all the answers

Describe the rotation of the stomach during embryonic development.

The stomach rotates 90° clockwise around its long axis during embryonic development. Signup and view all the answers

What is umbilical hernia and how does it occur?

Umbilical hernia occurs when the intestines herniate through an imperfectly closed umbilicus after returning to the abdominal cavity. Signup and view all the answers

What tissues may be contained within the wall of Meckel's diverticulum?

The wall of Meckel's diverticulum may contain patches of gastric and pancreatic tissues. Signup and view all the answers

What occurs during median (cranial-caudal) folding of the embryo?

The anterior and posterior ends of the embryo move ventrally, leading to the formation of brain vesicles and somites. Signup and view all the answers

How is the foregut formed during cranial folding?

Part of the endoderm of the umbilical vesicle is incorporated into the embryo, creating the foregut located between the brain and heart. Signup and view all the answers

What is the role of the septum transversum during embryonic development?

The septum transversum develops into the central tendon of the diaphragm, separating the abdominal cavity from the thoracic cavity. Signup and view all the answers

Describe the process of lateral folding and its significance.

Lateral folding is caused by the rapid growth of the spinal cord and somites, resulting in the incorporation of the midgut into the embryo. Signup and view all the answers

What happens to the connection between the midgut and the umbilical vesicle during lateral folding?

The initial wide connection is reduced to the omphaloenteric (vitelline) duct after lateral folding. Signup and view all the answers

What completes the closure of the ventral body wall in the developing embryo?

The ventral body wall closure is completed except in the region of the connecting stalk. Signup and view all the answers

How are the serous membranes formed during embryonic development?

The parietal layer of the lateral plate mesoderm forms the parietal layer of serous membranes, while the visceral layer forms the visceral layer lining the abdominal organs. Signup and view all the answers

What is the significance of the vitelline duct in embryonic development?

The vitelline duct serves as the temporary connection from the midgut region to the yolk sac and is eventually incorporated into the umbilical cord. Signup and view all the answers

What is the role of the greater omentum in the human body?

The greater omentum is a double-layered sac that extends from the greater curvature of the stomach to the transverse colon, providing support and protection to the abdominal organs. Signup and view all the answers

What are the primary symptoms of pyloric stenosis?

The primary symptoms of pyloric stenosis include projectile vomiting and polyhydramnios. Signup and view all the answers

How does the duodenum develop in the human embryo?

The duodenum develops from the caudal part of the foregut and the proximal part of the midgut, forming a C-shaped loop that becomes retroperitoneal. Signup and view all the answers

What causes duodenal stenosis?

Duodenal stenosis is usually caused by incomplete recanalization of the duodenal lumen. Signup and view all the answers

What distinguishes duodenal atresia from duodenal stenosis?

Duodenal atresia is characterized by a complete occlusion of the duodenal lumen, while duodenal stenosis involves partial occlusion. Signup and view all the answers

Describe the origin of the liver and biliary apparatus during development.

The liver and biliary apparatus originate from the hepatic diverticulum, a ventral outgrowth from the caudal part of the foregut. Signup and view all the answers

What is the significance of Kupfer cells in the liver?

Kupfer cells are specialized macrophages in the liver that play a crucial role in the immune response and the clearance of pathogens and debris from the blood. Signup and view all the answers

How do the celiac and superior mesenteric arteries contribute to the duodenum?

The duodenum receives blood supply from branches of both the celiac and superior mesenteric arteries due to its development from both foregut and midgut. Signup and view all the answers

What are the developmental origins of the inferior third of the anal canal?

The inferior third of the anal canal develops from the proctodeum, which is ectodermal in origin. Signup and view all the answers

Explain the significance of the pectinate line in the anal canal.

The pectinate line demarcates the border between the upper two-thirds, where internal hemorrhoids occur, and the lower third, where external hemorrhoids are found. Signup and view all the answers

What type of nerve innervation is responsible for the upper two-thirds of the anal canal?

The upper two-thirds of the anal canal are innervated by the autonomic nervous system. Signup and view all the answers

How do internal and external hemorrhoids differ in terms of pain sensation?

Internal hemorrhoids are covered by a mucous membrane that lacks pain receptors, while external hemorrhoids are covered by skin containing pain receptors. Signup and view all the answers

Describe the primary issue in Hirschsprung's disease.

Hirschsprung's disease is characterized by the absence of autonomic ganglion cells in a segment of the colon, leading to an inability to relax and propelling stool forward. Signup and view all the answers

List two functions of amniotic fluid in relation to fetal development.

Amniotic fluid provides a cushion to protect the fetus and serves as a reservoir of nutrients and fluid for fetal growth. Signup and view all the answers

What is the venous drainage for the lower third of the anal canal?

The venous drainage of the lower third of the anal canal is via the inferior rectal vein, which drains into the inferior vena cava. Signup and view all the answers

Why is amniotic fluid considered to have antibacterial properties?

Amniotic fluid has inherent antibacterial properties that help protect the fetus from infectious agents. Signup and view all the answers

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Study Notes

GI Anatomy and Development

Embryonic folding is crucial for the gut's cylindrical shape and occurs in two planes: median and horizontal folding.
The septum transversum forms the diaphragm's central tendon and separates the abdominal cavity from the thoracic cavity.
The foregut and hindgut develop from the endoderm, with the foregut located between the brain and heart, separated from the mouth by the oropharyngeal membrane.
The midgut forms as part of lateral folding, initially connected to the yolk sac via the omphaloenteric duct, later incorporated into the umbilical cord.
The developing abdominal wall consists of the somatopleure which forms the body wall and the splanchnopleure which forms the embryonic gut.

Serous Membranes and Mesenteries

Parietal layer from the lateral plate mesoderm lines the peritoneal, pleural, and pericardial cavities, while visceral layer lines the organs within these cavities.
The greater omentum is a double-layered sac extending from the stomach to the transverse colon.

Developmental Disorders

Pyloric Stenosis: Hypertrophy of pylorus causing projectile vomiting and obstructed food passage.
Duodenal Stenosis and Atresia: Stenosis is partial, typically due to incomplete recanalization; atresia is complete obstruction causing early vomiting with bile.
Congenital Omphalocele: Involves herniation of intestinal loops into the umbilical cord.
Gastroschisis: Malformation of the abdominal wall results in protrusion of the abdominal viscera into the amniotic cavity.
Meckel's Diverticulum: Remnant of the yolk stalk which can inflame, mimicking appendicitis.

Development of Organs

The duodenum develops from the caudal part of the foregut and proximal midgut, forming a C-shaped loop that becomes retroperitoneal.
The hepatic diverticulum from the foregut leads to the formation of the liver, gallbladder, and biliary ducts, with connections becoming narrower during development.

Blood Supply and Innervation

The duodenum receives blood supply from the celiac trunk and superior mesenteric artery due to its dual origin.
The anal canal is divided by the pectinate line into areas with different nerve, artery, venous drainage, and lymphatic drainage characteristics for the upper and lower thirds.

Hemorrhoids

Internal Hemorrhoids form in the upper 2/3 of the anal canal and lack pain receptors, causing minimal pain.
External Hemorrhoids occur in the lower 1/3, covered by skin with pain receptors, leading to discomfort.

Congenital Disorders of the Colon

Congenital Megacolon (Hirschsprung Disease): Characterized by absence of ganglion cells preventing colonic relaxation, leading to constipation and dilation.

Functions of Amniotic Fluid

Protects the fetus from trauma and infections and cushions the umbilical cord.
Serves as a reservoir of nutrients and provides necessary fluid for fetal growth and development of critical systems, including gastrointestinal and musculoskeletal systems.

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