Module 2B: Development Of Lymphatic And Digestive Systems Flashcards

Question

What is the main vein draining blood from the abdominal digestive organs? Inferior vena cava Renal vein Iliac vein Hepatic portal vein

Answer 1

Hepatic portal vein

Answer 2

Between the aorta and superior mesenteric artery

Answer 3

Superior mesenteric artery

Answer 4

Middle colic artery

Answer 5

Gonadal arteries

Answer 6

Hepatic veins

Answer 7

Common hepatic artery

Answer 8

Hepatic portal vien and haptic artery

Answer 9

Mesenteric veins

Answer 10

Superior mesenteric and splenic veins

Answer 11

Inferior vena cava

Answer 12

Superior mesenteric artery

Answer 13

Abdominal aorta

Answer 14

Abdominal aorta

Answer 15

Sigmoid colon

Answer 16

Vertebral column and abdominal wall

Answer 17

Renal Arteries

Answer 18

Superior and inferior mesenteric arteries

Answer 19

Adrenal glands

Answer 20

Common iliac arteries

Answer 21

Lesser curvature of the stomach

Answer 22

Inferior mesenteric artery

Answer 23

Return interstitial fluid to the bloodstream

Answer 24

Deep cervical

Answer 25

Produce RBC

Answer 26

Right arm and right side of head and thorax

Answer 27

From scratch formation from mesenchymal precursors

Answer 28

Cisterns chalk

Answer 29

Small intestine

Answer 30

• Fluid from plasma in the capillaries (red) diffuses into the interstitial space (IS) → interstitial fluid (IF) • Most is absorbed by tissue cells (pink) or resorbed into venous structures (blue) • ↑ Interstitial pressure is very damaging to structures in the IS • Lymph vessels are like an overflow valve, shunting accumulating IF away from the IS, eventually returning it to the venous blood

Answer 31

1. Vitelline veins, carrying blood from the yolk sac to the sinus venosus 2. Umbilical veins, originating in the chorionic villi and carrying oxygenated blood to the embryo 3. Cardinal veins, draining the body of the embryo proper. The lymphatic system begins mesodermally as a bilaterally symmetrical network arising from the cardinal veins.

Answer 32

Selective atrophy and remodeling of these early vessels lead to an asymmetric drainage pattern.  The thoracic duct, which drains most of the body (left head/neck, left upper limb, entire lower body), forms from the fusion of multiple lymphatic plexuses (e.g., cisterna chyli, retroperitoneal, lumbo-iliac).  The thoracic duct empties into the left venous angle (junction of left internal jugular and subclavian veins).  The right lymphatic duct, which drains the right upper quadrant, empties into the right venous angle.  This asymmetry reflects developmental remodeling of the original bilateral system into two distinct drainage pathways.

Answer 33

Two main hypotheses debated since the early 20th century: • Centrifugal hypothesis: • Lymphatic vessels sprout from veins ( lymphangiogenesis) • Centripetal hypothesis: • Lymphatic vessels form de novo from mesenchymal precursor cells ( lymphvasculogenesis) •Ongoing controversy for over a century •Recent evidence suggests both mechanisms contribute to lymphatic development

Answer 34

1. Capillary lymphatics: • Made of lymphatic endothelial cells (LECs) with discontinuous junctions that allow passive fluid entry from the surrounding interstitial tissues. 2. Collecting lymphatics: • Contain LECs with continuous junctions, intraluminal valves, lymphatic smooth muscle cells (LSMCs), and a continuous basement membrane. • Facilitate unidirectional lymph flow toward central circulation. • It provides a one-way drainage route from tissues back to the bloodstream via the great veins of the neck.

Answer 35

Structure and Function •Primary lymphoid organs (bone marrow, thymus): sites of immune cell production and maturation. •Secondary lymphoid organs (lymph nodes, spleen, mucosa-associated lymphoid tissues like Peyer’s patches, tonsils, adenoids): sites of lymphocyte activation. Major Lymphatic Ducts •The thoracic duct drains lymph from most of the body. •The right lymphatic duct drains lymph from the right side of the head and neck, the right thorax, and the right upper limb. Lymphoid Organ Organization •The spleen, Peyer’s patches, and lymph nodes are highly organized with distinct B-cell and T-cell zones. •This structure supports efficient adaptive immune response induction.

Answer 36

GALT is a key component of mucosa-associated lymphoid tissue (MALT).  Includes Peyer’s patches, isolated lymphoid follicles, appendix, and mesenteric lymph nodes.  Provides immune defense in the gastrointestinal tract. Prenatal Period: Postnatal Maturation:  Postnatal antigen exposure (microbiota, food) drives GALT expansion and maturation.  Germinal centers and IgA-secreting plasma cells develop.  Peyer’s patches sample luminal antigens.  Begins around week 11–12 of gestation in humans.  Initiated by interactions between intestinal epithelium, mesenchyme, and lymphoid tissue inducer cells.  Mesenchymal cells differentiate into lymphoid tissue organizer cells.  Formation of Peyer’s patches driven by VEGF-C and lymphotoxin signaling by week 20.

Answer 37

Relationship Between Cisterna Chyli and GALT: • Cisterna chyli is a dilated sac located at the lower end of the thoracic duct, typically at the level of L1–L2 vertebrae. • It serves as a major collecting reservoir for lymph from the intestinal trunk, lumbar lymphatics, and lower body. • The cisterna chyli is the central conduit for lymph originating from the GALT and surrounding abdominal organs, linking gut immunity with systemic circulation and helping maintain immune and metabolic homeostasis.

Answer 38

Proximal lower part of the Thoracic duct

Answer 39

Return interstitial fluid to the bloodstream

Answer 40

Deep cervical

Answer 41

Cardinal veins

Answer 42

Postitive pressure in the interstitial space

Answer 43

Lymphagiogenesis

Answer 44

Unidirectional lymph flow

Answer 45

Asymmetry due to selective remodeling

Answer 46

Thoracic duct

Answer 47

Left venous angle

Answer 48

Antigen exposure from microbiotat and food

Answer 49

Development of the esophagus, stomach, proximal duodenum, liver, gallbladder, and pancreas.. Foregut- includes the pharyngeal gut, and the remainder of the foregut that includes the esophagus, stomach, liver+ pancreas

Answer 50

Mechanisms and significance of physiological herniation and intestinal rotation Midgut - remains temporarily connected to the yolk sac via the vitelline duct. Includes duodenum, jejunum, ileum and ascending colon

Answer 51

Formation of the urogenital sinus and anal opening…… Hindgut- from transverse colon to the cloacal membrane

Answer 52

ectoderm and somatic mesoderm! Gives rise to the skin, body wall musculature, adn the parietal peritoneum (outer lining of the abdominal cavity) Encloses the entire body and eventually format the trunk and limbs

Answer 53

Splanchnic mesoderm! Forms the entire gastrointestinal tract, including the foregut, midgut, and hindgut. Which subsequently contributes to the development of associated organs such as the liver, pancreas, gallbladder a den parts of the respiratory system.

Answer 54

Lateral plate mesoderm, which splits into somatic and splanchnic layers!! The space brown these layers forms the intraembryonic coelom, which develops into the pericardial vanity (around the heart) pleural cavities (around the lungs), peritoneal cavity (around abdominal organs)

Answer 55

Ventral body wall is completely closed, except in the midgut region, where the connecting stalk (future umbilical cord) and the yolk sac are present The gut tube is also closed, except for a connection from the midgut to the yolk sac through the vitelline duct

Answer 56

Lateral folding - in the ventral direction pulls the amniotic cavity centrally - The lateral body wall of the embryo folds downwards. It consists of the partial layer mesoderm and overlying ectoderm - Vesceral mesoderm layers (surrounding the gut tube) are continuous with the parietal mesoderm layer through a membrane- the dorsal mesentery —> Dorsal mesentery extends from the caudal end of the foregut to the end of the hindgut Cephalocaudal folding - as the hold sac shrinks the cephalcaudal folding forces the shrinking hold sac towards the midgut region, away from the foregut and the hindgut

Answer 57

1.Head and Tail (Cephalocaudal) Folding: 1. The embryo undergoes a process of head and tail folding, where the cephalic (head) and caudal (tail) regions move toward the ventral side of the embryo. 2. Lateral Folding: 1. Simultaneously, the sides of the embryo undergo lateral folding, bringing the left and right sides closer together. 3.Formation of Cylindrical Structure: 1. These folding movements transform the flat trilaminar disc into a more cylindrical structure, creating the basis for the embryonic body shape. 4.Closure of Body Wall: 1 The folds eventually meet and close, forming a continuous body wall around the cylindrical embryo. 5. Establishment of Embryonic Axes: 1. The folding process establishes the three embryonic axes: anterior-posterior, dorsal-ventral, and left-right, providing spatial orientation for further development. .Differentiation of Regions: 1. As folding progresses, different regions of the embryo become more defined, setting the stage for the development of specific tissues and organs. Embryonic folding is a dynamic process that plays a crucial role in shaping the early embryo and establishing the foundation for subsequent organogenesis. It ensures that the basic body plan is correctly oriented and organized, allowing for the formation of complex structures during embryonic development.

Answer 58

1.Initiation of Folding: The embryo begins to fold along its longitudinal axis, initiating cranial-caudal folding. This folding process is essential for properly developing the neural tube and establishing the body's anterior-posterior axis. 2. Cephalic (Head) Folding: 1. Folding occurs more prominently at the anterior end of the embryo, leading to the formation of the head region. This process involves bending tissues to create the head and brain structures. 3. Caudal (Tail) Folding: 1. Simultaneously, folding occurs at the posterior end of the embryo, forming the tail region. This folding is crucial for the proper development of the posterior part of the neural tube and the tail structures. 4. Closure of Neural Tube: As the folding progresses, the neural tube continues to close along its length. The closure of the neural tube is vital for properly developing and protecting the central nervous system. 5.Establishment of Body Axes: 1. Cranial-caudal folding helps establish the anterior-posterior axis of the embryo, which is critical for the proper development of organs and structures along this axis. 6. Formation of the Gut Tube: Caudal folding contributes to the formation of the gut tube, which will eventually give rise to the digestive tract. This process is essential for the proper development of the gastrointestinal system. Cranial-caudal folding is a complex and coordinated process that lays the foundation for the subsequent development of organ systems and body structures. It is a fundamental step in the early embryonic development of vertebrates.

Answer 59

Dorsal neural tube, a notochord (derived from mesoderm) Paraxial mesodermal dominates (vertebrae skeletal muscles, and dermis) The developing embryo is organized into a tube-within-a-tube, which will develop into the gut and the outer tube is the body wall. Between these is the intraembryonic coelom, a fluid-filled body cavity that will give rise to the pleural, pericardial ,a peritoneal cavities.m **the intire structure is enclosed within a body wall derived from somatic mesoderm and ectoderm.

Answer 60

1.Bilateral Symmetry: —Vertebrates exhibit bilateral symmetry, dividing the body into two symmetrical halves. 2. Segmentation: —The body is often organized into repeating segments. (Somites) 3.Dorsal Nerve Cord (Neural tube): —Vertebrates have a dorsal nerve cord, developing into the spinal cord. (Neuralation) 4.Notochord: —A flexible, rod-like notochord provides support, and its vestiges form the intervertebral discs. 5.Vertebral Column: —The vertebral column surrounds and protects the spinal cord. (developed via the sclerotome of the somites) 6.Endoskeleton: —An internal skeleton made of bone or cartilage provides support. 7. Cranium (Skull): —Protects the brain and sensory organs. 8.Pharyngeal Arches: —Develop into gills, jaws, or throat structures. 9.Muscular System: —Well-developed for movement. (Thank you myotomes of the somites) 10.Digestive, Circulatory, Respiratory, Excretory Systems: —Specialized organs for processing food, circulating blood, obtaining oxygen, and eliminating waste. 11.Reproductive System: —-Specialized organs for sexual reproduction. 12.Nervous System: Includes a brain for processing information and coordinating body functions. These features form the foundation of the vertebrate body plan, adapting to diverse environments and species.

Answer 61

The epithelial lining of the digestive tract ‒ Epithelium modifies to form secretory cells such as hepatocytes and the exocrine and endocrine cells of the pancreas.

Answer 62

The stroma for the glands ‒ Muscle, connective tissue, and other components of the wall of the gut

Answer 63

• The foregut is temporarily closed by an ectodermal–endodermal membrane called the oropharyngeal membrane • An ***oropharyngeal membrane separates the stomodeum (the primitive oral cavity derived from ectoderm) from the pharynx (a part of the foregut, derived from endoderm) • In the 4th week, the oropharyngeal membrane ruptures, establishing an open connection between the oral cavity and the primitive gut

Answer 64

The hindgut also terminates temporarily at the ***cloacal membrane • This membrane separates the upper part of the anal canal from the lower part, called the ***Proctodeum • The membrane breaks down in the 7th week to create an opening (the anus) to the cloaca

Answer 65

The lower part of the anus

Answer 66

Oral cavity - the oropharyngeal membrane separates the stomodeum from the pharynx

Answer 67

respiratory diverticulum

Answer 68

1) the different rates of growth in various regions of the stomach wall and 2) the changes in position of surrounding organs ***During positional changes, the stomach rotates both around a longitudinal axis and an anteroposterior axis Clockwise Rotation along the longitudinal axis

Answer 69

Slightly downward

Answer 70

• The visceral mesoderm layer on the outside starts to proliferate • This creates an apron-like structure called the Greater omentum

Answer 71

As the stomach rotates, the duodenum rotates to the right The rapid growth of the pancreas swings the duodenum from its initial midline position to the right side of the abdominal cavity

Answer 72

During the second month, the lumen of the duodenum is initially blocked due to the proliferation of cells in its walls. However, the lumen is recanalized shortly after

Answer 73

endodermal epithelium Hepatic diverticulum

Answer 74

Septum transversum Central Liver

Answer 75

The fetal liver begins functioning early in development and plays several vital roles before birth. Initially, it serves as a major hematopoietic organ, producing red and white blood cells beginning around the 6th week of gestation. This hematopoietic activity peaks during the second trimester and gradually declines as the bone marrow assumes this role. In addition to hematopoiesis, the fetal liver contributes to metabolic activities, including glycogen storage and limited plasma protein synthesis (such as albumin and clotting factors). However, its detoxification function is minimal during fetal life, as the placenta primarily handles this role. Although structurally developing by week 4, the liver's full enzymatic and metabolic capacity remains immature at birth and continues to mature postnatally.

Answer 76

•Hepatocyte Development: By week 12, the fetal liver is structurally well-developed. Hepatocyte cords have formed, contributing to the epithelial lining of the bile system. •Formation of Bile Canaliculi: Specialized channels between hepatocytes. Enable transport of bile from hepatocytes into the developing billary network. Critical for initiating bile secretion. • Intrahepatic Bile Duct Development: These ducts branch throughout the liver parenchyma. Connect bile canaliculi to the extrahepatic biliary tree. • Extrahepatic Bile Duct and Gallbladder Formation: Structures including the gallbladder and cystic duct develop concurrently. Allow for bile storage and its eventual transport to the duodenum.

Answer 77

Two endodermal buds •The pancreas develops from dorsal and ventral buds that approximate and fuse during gut rotation. —-A dorsal pancreatic bud (arises directly from the duodenum) —-A ventral pancreatic bud (arises near the bile duct) •As the duodenum rotates and shifts rightward: —The head, neck, and body of the pancreas are pushed against the posterior abdominal wall. The overlying peritoneum fuses and resorbs, making these parts developmentally retroperitoneal. —The tail of the pancreas remains intraperitoneal. ** The ventral bud comes to lie immediately below the dorsal bud Later, the tissues and the duct systems of the dorsal and ventral pancreatic buds fuse together In the 3rd month of fetal life, pancreatic islets (of Langerhans) develop from the pancreatic tissue and scatter throughout the pancreas Insulin secretion begins during the fifth month

Answer 78

1) Rapid elongation of the gut and its mesentery, resulting in formation of the primary intestinal loop 2) The cephalic limb of the loop develops into the end part of the duodenum, the jejunum, and upper part of the ileum 3) The caudal limb becomes the lower portion of the ileum, the cecum, the appendix, the ascending colon, and the proximal two-thirds of the transverse colon

Answer 79

superior mesenteric artery

Answer 80

Rapid elongation of the primary intestinal loop, particularly of the cephalic limb, together with the rapid growth and expansion of the liver —> the abdominal cavity is too small at that time to contain all the intestinal loops —> causes the intestine loops to enter the umbilical cord during the 6th week of development —> physiological umbilical herniation - Occurews between Weeks 6-10 of embryonic development - rapid elongation of the midgut - large size of the developing liver and kidneys restricts abdominal space -the growing midgut hernia ties into the umbilical cord

Answer 81

• This midgut herniation is accompanied by a 270° anticlockwise midgut rotation in the abdominal cavity. • Return into the body is caused by the rapid growth of the body or a decrease in the length of the mesentery. Midgut Loop Formation: • The midgut forms a U-shaped loop around the superior mesenteric artery (SMA). • Divided into two limbs: • Cephalic limb (cranial portion) • Caudal limb (caudal portion) Derivatives: Cephalic limb becomes: • Distal duodenum • Jejunum Part of the ileum Caudal limb becomes: • Distal ileum • Cecum • Ascending colon • Proximal two-thirds of the transverse colon •Rotation: During herniation: 90° counterclockwise rotation around the SMA. During return (around week 10): additional 180° counterclockwise rotation. • Total: 270° counterclockwise rotation ensures proper intestinal positioning. • Return to Abdomen: • Midgut returns to the abdominal cavity as it enlarges. • The cecum descends to the lower right quadrant. •Clinical Relevance: Abnormalities can result in: Malrotation Volvulus (twisting of the bowel) Omphalocele (failure to return to the abdomen)

Answer 82

defect that occurs when intestinal loops, which normally herniate into the umbilical cord during the 6th to the 10th weeks of gestation (physiological umbilical herniation), fail to return to the body cavity Amnion is the sac surrounding the intestinal loops q

Answer 83

is a rare congenital abnormality characterized by a mirror-image transposition of both the abdominal and the thoracic organs • Results in failure to generate normal left- right laterality

Answer 84

to the distal third of the transverse colon, the descending colon, the sigmoid colon, the rectum, and the anal canal

Answer 85

cloacal membrane

Answer 86

Allantois: An extraembryonic membrane, like the amnion and chorion. •Appears as a small tubular outpouching from the hindgut, extending into the connecting stalk. •Unlike the amnion and chorion (which are primarily protective), the allantois: — Functions in early waste collection and fluid exchange. — Plays a minor role in reproductive development. • Later forms the urachus, which becomes the median umbilical ligament in the adult. (More on Allantois with GU development). **Relationship to the Cloacal Membrane •The allantois connects to the hindgut, which terminates at the cloaca, a common cavity for digestive and urinary outflow. •The cloacal membrane lies over the cloaca and is composed of surface ectoderm. •As the urorectal septum forms: The cloaca is divided into: Anorectal canal (posterior) - gives rise to the rectum and anal canal. • The cloacal membrane ruptures, creating the anal opening for the hindgut and an opening for the urogenital sinus (covered by the urogenital membrane). • Urogenital sinus (anterior) - associated with the allantois and becomes part of the urinary bladder. The endoderm of the hindgut forms the internal lining of the bladder and urethra •Thus, the urinary bladder is derived from the portion of the hindgut originally associated with the allantois.

Answer 87

•The allantois is a small extension from the hindgut that enters the cloaca, a shared cavity for urinary and digestive outflow. •The cloacal membrane initially covers this region externally. •The urorectal septum grows downward, dividing the cloaca into: • Anterior urogenital sinus → associated with the allantois, forms part of the urinary bladder • Posterior anorectal canal → becomes the rectum and anal canal •The cloacal membrane ruptures, forming separate openings for the anal and urogenital tracts. •The urinary bladder ultimately derives from the cloacal region linked to the allantois.

Answer 88

The heart lies outside the thorax, and there is a cleft in the thoracic wall

Answer 89

Intestines herniate through the abdominal wall to the right of the umbilicus

Answer 90

Closure in the pelvic region has failed

Answer 91

A larger closure defect in which most of the pelvic region has failed to close, leaving the bladder, part of the rectum, and the anal canal exposed

Answer 92

Oropharyngeal membrane

Answer 93

Two (longitudinal and anteroposterior)

Answer 94

Lateral plate mesoderm

Answer 95

Cloacal membrane

Answer 96

Omophalocele

Answer 97

Cloacal memebrane

Answer 98

Urorectal septum

Answer 99

Repaid intestinal and liver growth

Answer 100

Vitelline duct

Module 2B: Development Of Lymphatic And Digestive Systems Flashcards

(140 cards)