Human Embryology Flashcards

Flashcards review for Human Embryology exam.

What is the laryngotracheal diverticulum?

Out pocketing of region of foregut, behind the oropharyngeal membrane.

Where does the laryngotracheal diverticulum derive from?

Behind the protochordal membrane

How does the laryngotracheal diverticulum divide into the esophagus and trachea?

Primary and secondary bronchus, 2 bronchi on right and 3 on left.

What happens during the lung bud stage (embryonic)?

Primary bronchiole buds happening in 5th week

What happens during the pseudoglandular stage?

More branching, we get terminal or respiratory bronchiole, mesoderm gets vascularly during that time, muscularize, respiratory bronchioles

What happens during the canalicular stage?

Blood vessels cut and make contact, important for lungs to work properly as when you inhale air comes in to those sac and you have to have the vasculature in order for gas exchange to occur

What happens during the saccular stage?

Primitive alveoli

What happens during the alveolar stage?

You can establish gas exchange, final divide in 27 weeks, which continues until childhood

When are the lungs fully mature & functional?

Post 24-28 weeks (7th month)

What is esophageal atresia?

When esophagus forms into two separate segments and prevents the baby from not swallowing and if you can’t swallow then there would be too much fluid in amniotic cavity.

What is a tracheal-esophageal fistula?

When the esophagus and trachea doesn’t cut off properly, so there is an abnormal connection.

What clinical issue can be associated with both esophageal atresia and tracheal-esophageal fistula?

Failure of the laryngotracheal to branch or to cut off from the esophagus

What is the timing of early heart formation?

18-19 days in the 3rd week

Where and how does the heart develop in the 3rd week?

At the cardiogenic region, during that time 2 primitive or endocardial heart tubes join creating a single linear heart tube, and folding occurs.

When is fusion of the heart tubes?

At 23 days fully but start to fuse 21 days.

What are the first subdivisions of the primitive heart tube?

Bulbus Cordis, primitive ventricle, primitive atrium, and sinus venosus

When does the heart start beating and how does blood flow?

Day 22 heart starts to beat, blood comes in from bottom then through the heart. Bloods flood into sinus venosus to the atrium to the ventricle then to the bulbus cordis to the heart.

How many subdivisions does the heart have at 23 days?

Trunchus arteriosus (5 confirm with professor) which is a chamber is added.

What is the bulboventricular loop?

The bending of the heart tube which forms C-shape loop which position the ventricles in the mature heart with the right ventricle. Brings atrium up on the heart and to the left which is caused by elongation causes by the bulboventricular loop.

What does the embryonic heart look like at the end of the first month?

It is just a tube, the chambers just started to form, signs of division, dog ears growing as extension of the atria (one atria), and the oracle which are extensions of the atria, also one ventricle and one ventricle (ask miss). Also atria above ventricle.

What are the endocardial cushions and what do they divide?

Swellings that develop in the dorsal and ventral walls of the atrioventricular canal. Little bulbs that appear, starts growing from inside of heart where they fused in about the 5th week, they divide into two canals, which forms the valve of the heart. When they fuse, they divide into atrioventricular canal then right and left channel. The walls are the septum that separates the atria top chamber from the ventricles (bottom chamber)

How do the atria separate, and what structures are involved?

Division of atrium begins with the appearance of a crescent-shaped membrane that appears in the roof and grows ventrally toward the endocardial cushions. Separated by the interatrial septum or by miss definition the septum primum. How does this change after birth? Fossa ovale.

What does the sinus venosus give rise to in the fully developed heart?

Smooth, posterior part of the right atrium. Known as the sinus venarum

How does the truncus arteriosus subdivide, and what does it form?

It does not divide instead it becomes the aorta and pulmonary artery (ask miss)

Describe the formation of the interventricular septum.

Forms from the muscular septum (thick wall), and part of it derives from bulbar ridges, truncal ridges and endocardial cushions which becomes the membrane of the adult IV septum, what forms the muscular septum? Thick wall. The membranous septum? bulbar ridges, truncal ridges endocardial cushions

What does the bulbus cordis give rise to in the fully developed heart?

Incorporated into the Right Ventricle as the Conus arteriosus or infundibulum The left portion of the bulbus cordis is Incorporated into the Left Ventricle as the aortic vestibule.

What happens in Atrial Septal Defects (ASD)?

Interatrial septum fails to form properly.

What is an Atrioventricular Septal Defect also called?

Endocardial cushion defect; This causes a hole in the center of the heart and is affiliated with down syndrome

What happens in Ventricular Septal Defect (VSD)?

Interventricular septum incomplete and fails to fully divide ventricles

What is Dextrocardia?

Heart goes to the right instead of the left, this is because the bulbus ventricular loop to the left instead of the right causing it to go on the other side. Also, this allows the truncus arteriosus to connect the wrong out flow track to the ventricle.

What happens in Persistent truncus arteriosus?

Failure of aorticopulmonary septum to form; Necessarily includes VSD; Results in mixing of blood from R&L sides of heart; Can be fatal if untreated

What happens in Transposition of Great Arteries?

Aorticopulmonary septum does not spiral; mixing of blood through patent foramen ovale or ductus Arteriosus

What happens in Unequal Division of Truncus Arteriosus?

One artery large, other small (stenotic);Ventricle on stenotic side must work harder, typically hypertrophies; Often aorticopulmonary septum not aligned with interventricular septum and have VSD

What is Tetralogy of Fallot?

Combination of defects: pulmonary stenosis, VSD, Overriding aorta, Hypertrophy of right ventricle

When does vasculature begin to develop, and where?

Third week, circulatory system establish but 5th week is really when blood formation starts and in the mesodermal layer; Occur in liver, bone marrow and lymph nodes

What is angiogenesis?

Forming new blood vessels from existing ones or from reaping apart vessels and reconstructing them.

How does the development of the branchial arches relate to the development of the great vessels?

Aortic arches which are paired arteries running within the branchia arches give rise to the great vessels, we develop 1,2,3 aortic arches and when we reached the 4 the 1st arch disappear then the 6 comes in

Which aortic arches form in humans?

1,2,3,4,6 no 5

How does the path of the vagus nerve relate to the aortic arches?

The vagus nerve in the thorax gives off a branch that’s closely associated with aortic arch which is on the left side of the body, it dives underneath the aortic arch and becomes the laryngeal nerve/ left recurrent laryngeal nerve.

Understand the major differences between adult and fetal circulation.

Fetal circulation uses ductus arteriosum and ductus venosus Umbilical vein brings oxygenated blood from placenta to right atrium which shoots from foramen ovale to left atrium which it bypass the lungs (atria to atria)= fossa ovalis, then some of the blood bypass the lungs a second time and go to the ductus ateriosus (pulmonary artery to aorta)= ligamentum arteriosum. Return blood to placenta by umbilical artery. Adult circulation uses liver and lungs for gas exchange, as ductus arteriosum and ductus venosus closes. Ligamentum teres/ Round ligament of the liver, blood comes from body into right atrium, cannot cross over, goes down then to the lungs come back goes down then go outthe aorta

What happens in Patent Ductus Arteriosus?

If the ductus arteriosus fails to close off or involute, it can lead to significant volume of aortic blood flow being diverted to the lungs; Can lead to mixing of blood.

What happens in Coarctation of the Aorta?

Narrowing of the aorta, usually just above (preductal) or below (postductal) the ductus arteriosus.

What happens in Double Aortic Arch?

When you do not lose the connection that you are to you’re left with a remnant, a very small arch and a combine situation where you’re pinching the trachea and esophagus can be deadly if compression is significant enough to affect breathing.

What happens in Right Aortic Arch?

we are suppose to have a left aortic arch instead of a right

Based on embryological development, how do we define the foregut?

The fore Gut is everything anterior to the mid gut

What is the Midgut?

Part of the Gut that is connected to the vitelline duct

What is the Hindgut?

The hind gut is everything posterior to the mid gut

What is the dorsal mesentery?

Double layer sheet of peritoneum that separates the hind gut from the dorsal wall

What will the dorsal mesentery become?

Greater momentum, Meso duodenum, mesentery proper and dorsal meso-colon

What are the hepatopancreatic & dorsal pancreatic diverticula?

The dorsal pancreatic diverticula are an outpouching of the foregut that forms the dorsal portion of the pancreas as it comes up from the foregut and into the dorsal mesentery, specifically the body and tail. Hepatopancreatic diverticula it is the outpouching of the duodenum or gives posterior ebd of the septum transversum, which occurs close to the midgut, which is a hollow tube which also home both liver and pancreas.

What is the ventral mesentery and how is it formed?

It is a double layer of peritoneum that suspends the primitive gut tube in the peritoneal cavity and attaches the liver to the anterior abdominal wall. It is formed when the hepatopancreatic diverticulum splits giving the ventral pancreatic diverticulum which hugs the back end of septum transversum and the hepatocystic diverticulum which grows more anteriorly into the septum transversum giving rise to liver and gall bladder as it splits into the cystic and hepatic diverticulum.

What will the ventral mesentery become?

Falciform ligament and lesser momentum

What is foregut rotation?

When the fore gut rotates clockwise at 90 degree, How does it rotate and what are the consequences? where the left side moves ventrally and the right side moves dorsally, and its consequences are -

How does the pancreas form?

Formed when the duodenum rotates and shifts the dorsal and ventral pancreas from being up and down to more horizontal, causing the Meso duodenum to shift with it and as it continues to shift, the ventral pancreas rotates around the duodenum until it ends up touching the back of the dorsal pancreas. Ventral pancreas is it’s own thing with the common bile duct attach to it and also it’s at the distal end of the duodenum while the dorsal pancreas is the proximal part of the duodenum

Describe the formation of the lesser sac.

liver grows so much a touch back wall of the embryo in region of inferior vena cava, upper mesogastrium moves posteriorly up against back wall of embryo. Remnant of right peritoneal diverticulum that we block off

What is a physiological umbilical hernia?

part of your intestine bulges through the opening in your abdominal muscles near your bellybutton (navel).

What does retroperitoneal mean?

This is the space behind the peritoneum and when you’re not mobile. All gut things are retroperitoneal.

Which structures are secondarily retroperitoneal and why?

Those which were initially suspended in the mesentery, then later migrated posterior to the peritoneum during development and includes the duodenum (except for D1 – proximal segment), ascending and descending large bowel and the pancreas (except the tail). In other words you had a mesentery then you lost them

Describe the formation of the greater omentum, gastrocolic ligament and transverse mesocolon.

greater omentum- gastrocolic ligament - transverse mesocolon-

What is an omphalocele?

Abdominal viscera herniating into the base of umbilicus

How does omphalocele differ from a congenital umbilical hernia and gastroschisis?

Intestine protruding through abdominal wall defect

What different things can occur if the vitelline duct does not degenerate?

Meckel’s Diverticulum or umbilical-ileal fistula is a congenital defect in the small intestine. If your child develops symptoms, they can have surgery to remove it. A fistula opening between two structures that are not meant to be join (mid-gut and belly bottom)

What is volvulus?

Mal rotation of bulb that causes obstruction of some kind. Volvulus is an abnormal twisting of part of the large or small intestine

What is a subhepatic cecum?

The subhepatic position of the cecum and appendix is a normal variant which might present a diagnostic dilemma in cases of acute appendicitis because tenderness in such cases is not typically located at McBurney's point.

What is an annular pancreas?

An annular pancreas is a rare congenital deformity that affects the pancreas. It happens when the pancreas doesn’t develop as it should, and a ring of extra pancreatic tissue forms around the first part of the small intestine. This tissue can cause a number of symptoms and disrupt the digestive process and other bodily functions.

What is Pancreas divisum?

Pancreas divisum is a congenital disorder where the pancreatic ducts do not join properly. It occurs when two parts of the pancreas fail to fuse together during development, leaving the main pancreatic duct to drain through a smaller opening.

What is Hirschsprung’s disease and why does it occur?

Hirschsprung's disease occurs when nerve cells in the colon don't form completely. Nerves in the colon control the muscle contractions that move food through the bowels. Without the contractions, stool stays in the large intestine. Failure of neutral crest to invade parts of the colon

Define the three nephric systems that develop.

Pronephros development, mesonephros, and metanephros.

What do the three nephric systems form in the adult?

Pronephros development forms in neck and are the first kidneys which are non- functioning, they disappear as they start forming, and they initiate the second set of kidneys mesonephros (largest one, fully function as a kidney until the final kidney is fully develop and functional), the metanephros then form last in 5th week.

What is the ureteric bud?

Sprot from the mesonephric duct that appears during the embryological development of urogenital organs.

What does the ureteric bud become?

urinary collecting system of the kidney (ureters, renal pelvis, major calyces, collecting ducts, nephrons)

What is meant by “ascent” of the kidneys?

Describe the dual induction of collecting and excretory system formation.

What happens when the renal artery obstruct the ureter?

impact outflow of urine

What happens in Agenesis?

no kidney at all; Can contribute to oligohydramnios

What happens in Unilateral Renal Agenesis?

Failure of ureteric bud to develop

What happens in Polycystic Kidney?

Cyst in kidney what you do is you sacrifice the tissues of the kidney for the fluid fill sac taking from the efficiency of the kidney making it hard for the kidney to do its job

What happens in Supernumerary kidney?

resulting from two ureteric buds- Three kidneys with their separate ureter

What happens in Malrotation of kidney?

(kidney rises and never turn in)

What happens in bifid ureter with supernumerary kidney?

Bifid Ureter- Two kidneys that share one ureter, which will result in urine is going to be trucked and hangs out in a specific portion of the ureter, which can cause UTI

What happens in Ectopic Kidney – Crossed Renal?

Fused Kidneys that have their own ureter that goes to the correct place but both kidneys are at the same side of the lower abdomen.

What happens in Supernumerary Vessels?

This is where you have multiple renal arteries and veins, which is caused when the kidneys ascend and some of the arteries and veins don’t dry up.

What happens in Pelvic Kidney and Divided Kidney with Bifid Ureter?

This is where you have a ureteric bud that forms then divide into two that when it goes into the mesonephric mass it forms two separate part of the kidney with their separate attachment that fuses at the bottom end and attaches to the ureter.

What happens in Ectopic kidney’s?

Not in right place, as they are in the pelvis called pancake or discoid kidneys, as it is a fuse mass of kidney. They never ascend

What happens in Double Kidneys?

Two ureteric bud instead of one ureteric bud, gives two kidney’s on one side

What happens in Cross Ectopia?

Kidneys are on the same side of the body, ureter crosses the midline to attach into the bladder.

Describe the formation of the urinary bladder and urethra.

Derive from end of gut tube which derives from endoderm. The cloacal is partitioned into urethra bladder. The bladder is in front and rectum in back both made from endoderm. The ureters, which have formed as outgrowths of the mesonephric ducts, enter the bladder at the base of the trigone (made from the inside out terminal end of the mesonephric duct made from intermediate mesodem).

What is a cloacal septation?

This is where the urogenital sinus and the rectal passage (bladder and rectum separates) divides

How does cloacal septation occur?

Occurs when the Tourneux (comes from the front and aims from the cloacal membrane) and the left and right Rathke folds (coming towards midline) come together.

What happens if cloacal septation goes wrong?

Failure of the Tourneux and Rathke folds to form may results in a fistula between the rectum and bladder. Fistula can go towards prostate (retro- prostatic), retro- vascular fistula, Patent Urachus fistula connecting bladder and umbilical cord causing urine to come out of belly button. Urachal cyst is when fluid and tissue that forms between the bladder and belly button

What is the difference between genetic sex, gonadal sex, and somatic sex?

Genetic sex- xx female xy male; Gonadal sex- testes and ovaries; Somatic sex- When we talk about secondary sexual characteristics. DISTRIBUTION OF BODY hair, FAT AND GENITALIA. Fetal sexual differentiation of the gonads, the internal reproductive tract and the external genitalia.

How do gonads develop?

Intermediate mesoderm forms gonadal ridge. The gonadal ridge then forms both the urinary system and gonadal section/ reproductive system, to initiate formation of gonads. Primordial germ cells migrate to the Dorsal mesentery then head to the cathedral where things get crazy, hen to the gonadal cord of the gonadal ridge as they pushes their way through cathedral fighting to see what becomes what type of cell. Support cells hang out which gives message what they are going to do when they get the message is shove the cells in the walls of the cathedral and actually corporating them self into the gonadal cord. Genes in their will tell you to be male or female. Germ cells migrate from near the allantois and colonize the primordial gonads then migrate to Dorsal mesentery then they head to cathedral or gonad cords, then support cells are in their that gives the message of what they are going to be, then once you get it they put you in the wall of the cathedral and combine then with the gonad cord. Then if you have testes determine factors you develop testes and it’s also because of the medulla at the gonadal ridge.

Describe the “dual” genital duct system

This is where we have both mesonephric duct and paramesonephric duct or Mullerian duct (is a novel structure, which has nothing to do with kidney development and is also from intermediate mesoderm) which is on the opposite side to the mesonephric duct and dumps into same urogenital sinus. Only in females does the paramesonephric duct turns into reproductive organs. Mesonephric duct or Wolffian duct is left over from kidney development, which is used to drain products from initial kidneys.

Describe derivatives of the urogential sinus, mesonephric duct & paramesonephric duct in males.

all endoderm, mesonephric duct (left over from kidney develop)& paramesonephric duct in males (from intermediate mesoderm which has nothing to do with kidneys but only in females they turn in reproductive organs); Males turns paranephric duct into vas deferens.

What is hypospadias?

Opening to urethra inferiorly due to failure of zipping up, which is located under the penis and scrotum, which causes gaps or holes and urine and sperms won’t be able to come through the tip.

What is Epispadias?

Opening on the superior surface of the penis, caused by opening on anterior abdominal wall , like showing organs which aren’t suppose to be showed.

Describe maculinization of the indifferent external genitalia, and how it is induced.

Background Knowledge- Refers to the stage at 9 weeks when genitalia is identical, If Y chromosome, testosterone, induces external male gentalia to form Tubercle (clitoris/glans, Fold (minora/ urethral raphe), swelling (labia majoria/scrotums) are all shared. In Males tubercle becomes glans, the folds close of the urogenital sinus and becomes the urethral raphe and the the Swelling become the scrotum.

How does the gonad move after development?

Male gonads are outside the body or on the outside surface of the anterior abdominal wall, The push through the anterior abdominal wall and drag it’s components to the scrotum and hangs outside the body because of temperature. The testes is attach to a string called the gubernaculum which is a structure that has one side attached to testis and the other to the scrotum. Through differential growth testes gets pulled into the scrotum as a results of the shortening of the gubernaculum, when it does that is drags a bulb of peritoneum with it called tunica vaginalis

Describe derivatives of the urogential sinus, mesonephric duct & paramesnoephric duct in females.

urogential sinus- Urethra and vaginal vestibules; mesonephric duct- Regresses, but leave remnants which are Gartner’s duct and Epoophoron, Paroophoron; paramesnoephric duct- uterus, fallopian tube/ uterine tube, cervix, and the upper part of the vagina

What is Turner Syndrome?

Caused when a female is born with missing or incomplete X chromosome.

Describe the origin of the vagina and uterus.

When urogenital sinus is portioned from uterus and vagina we get another opening, it causes the sinovaginal bulbs (thick bulb of tissue in posterior wall of urogenital sinus, sinovaginal bulbs extends as a pillar of endoderm and extend the column of tissues posteriorly a little bit, it then opens up and preliferate giving the vagina and uterus.