• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/315

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

315 Cards in this Set

  • Front
  • Back
What causes club foot?
olgiohydramnios
What causes Phocomelia (meromelia, amelia)?
Thalidomide
What causes Digital hypoplasia?
dilantin
What are the 3 disruptions?
club foot, phocomeila, and digital hypoplasis
What causes Rocker bottom feet?
Trisomy 18 (Edwards)
What causes Achondroplasia?
FGFR3 defect
What causes Syndactyly?
Mutation in pro-apoptotic genes
What causes Polydactyly?
Over-expression of growth or patterning factors
What causes Postaxial deletion?
Wnt-7a mutation
What causes Synpolydactyly?
Hoxd13 defect
What causes Holt-Oram syndrome? What is Holt Oram-Syndrome?
TBX5 defect
autosomal dominant heart-hand syndrome
What is the spleen derived from?
Only mesoderm (NO ENDODERM)
Where does skeletal and CT of limb arise?
lateral plate mesoderm
What is the Apical Endodermal Ridge?
The epithelial thickening at the distal tip of each limb bud
What is the Progress Zone?
mesenchyme adjacent to AER, area of proliferative cells that remain undifferentiated until the distal tips of the digits are formed
In what kind of sequence do mesenchyme condensations of the long bones begin to appear?
proximodistal
Upper limbs rotate ______
Lower limbs rotate _______
lateral, medial
What 3 factors are apoptosis of the interdigital webbing dependent on?
the Bone Morphogenetic Protein (BMPs), a family of growth factor proteins and other proteins that promote patterning

Cellular Retinoid Binding Proteins (CRBPs)

vertebrate homologue of Muscle Segmentation Homeobox, MSX1 protein.
What are the 2 types of genes that play a role in limb development?
growth factors and homeobox genes

Growth factors control cell growth and proliferation.

Homeobox genes (box of TF) specify identity and spatial arrangement of body segments and organs.
What are the 3 axes of limb growth?
• proximodistal,
• anteroposterior
• dorsoventral.
What controls proximodistal growth?
Fibroblast Growth Factors from the AER
Those cells that remain under the influence of the AER for a longer time form progressively more distal or proximal limb structures?
distal
What establishes patterning along the anteroposterior axis?
Sonic hedgehog
Where is SHH expressed?
Shh is expressed in a discrete region along the posterior border at each stage of limb bud development, located most proximally early and more distally later.
What happens in the case of additional posterior expression of SHH? Additional anterior expression? What happens with a lack of SHH?
extra posterior digits

extra anterior digits

lack of digits
What is retinoic acid? What do excessive amounts result in? Where is it expressed?
transcriptional activator for specific pattern-forming genes (which include shh) during limb development.

congenital abnormalities.

posterior limb mesenchyme.
What establishes dorsal ventral patterning? Where is it expressed? What does it do? What is En-1? What happens with En-1 expression in the dorsal ectoderm?
Wnt-7a

Dorsal Mesoderm

induces expression of genes in the dorsal mesoderm of the limb bud and Wnt-7a and these other genes give the limb its dorsal characteristics, darker thicker hair on the skin and extensor muscles.

Engrailed-1 (En-1) is a TF activated by signal transduction and expressed in the ventral ectoderm.

Wnt-7a suppresses En-1 expression in the dorsal ectoderm, preventing double ventral pattern.
What do the products of HoxA and HoxD genes do? What axes do they effect?
The products of these homeobox genes are transcription factors that specify identity and spatial arrangement of body segments.

anteroposterior and the proximodistal axes
What is a malformation?
A malformation is a morphological defect that results from an intrinsically abnormal developmental process, such as a chromosomal abnormality like Trisomy 18 or a gene mutation like Achondroplasia and Synpolydactyly, among other possibilities.
What are disruptions?
A disruption is a morphological defect that results from the extrinsic breakdown or interference with an originally normal developmental process. Teratogens are environmental agents or drugs that cause morphological defects. The drugs Thalidomide and Dilantin can cause limb defects.
What is a deformation?
A deformation is an abnormal form, shape, or position of a body part that is correlated with unusual mechanical forces during development. For example, oligohydraminos (low volume of amniotic fluid) can result in club foot.
What is a dysplasia?
A dysplasia is an abnormal organization of cells into tissue and morphological structure. Dysplasias are not common to limbs.
Where does the ventral mesentary undergo apoptosis? Why?
Caudal to the liver

allows for folding and rotation of the digestive tract
What is the midgut originally continuous with? What are the foregut and hindgut closed off by?
yolk sac,

oropharyngeal and cloacal membranes
What type of mesoderm is the digestive tract surrounded by? What will that mesoderm form?
Splanchnic

muscle and CT
As the embryo undergoes embryonic folding and elongation, so too does the dorsal mesentery, which curves into a C-shape within the median plan, along the ____________ axis
anterior-posterior
What does the reduction of ventral mesentery allow for?
folding and rotation of the digestive tract.
What are the 4 regions of the dorsal mesentery?
mesoesophagus (containing the esophageal region of the foregut)

mesogastrium (containing the gastric region, e.g., stomach and pancreas, and more anterior duodenal region)

mesoduodenum (containing the posterior duodenal region and the midgut)

mesocolon (containing the hindgut)
What arteries supply the foregut, midgut, and hindgut?
celiac artery

superior mesenteric artery

inferior mesenteric artery to the hindgut
What is the esophagus suspended in?
What does it give rise to?
mesoesophagus and mesogastrium

lungs (laryngotracheal diverticulum)
Where does the stomach start its formation?
within dorsal mesentery (mesogastrium) and the ventral mesentery derived from the septum transversum
When does the stomach undergo a process of rotation?
When the stomach travels below the diaphragm
What generates the lesser sac, an invagination in the dorsal mesogastrium?
90 degrees in a clockwise rotation of stomach
What does the enlargement of the lesser sac create?
greater omentum, a pouch which will become located inferior to the level of the stomach.
As the dorsal side of the stomach (which becomes directed towards the left side of the body) grows faster, what is generated?
greater convex curvature and fundus
What 4 organ systems are outgrowths of the endodermal digestive tract?
lungs, liver, gall bladder, and pancreas
How does the liver start its growth?
The liver grows as an evagination of the ventral surface of the foregut (the duodenum) into the septum transversum (ventral mesentery).
What 2 buds make up the initial liver? What becomes of the common connecting stalk?
cranial and caudal buds.
becomes the common bile duct.
What does the cranial liver bud become? What about its neck?
right and left lobes of the liver, and ultimately differentiates the numerous hepatic cords.

hepatic duct
What does the caudal liver bud become? What about its neck?
gall bladder

cystic duct
What do the hepatic cords invade? What do they form anastomosis around?
blood vessels within the septum transversum

primordial hepatic sinusoids.
What secretes bile into the bile canaliculi at week 12? What does the bile caniculus grain into
Hepatocytes

bile duct.
What does enlargement of the liver help?
displacement and 90 degree clockwise rotation of the stomach
The spleen is made of only _________
What does it form inside of?
mesoderm
dorsal mesogastrum (greater omentum)
What are the two buds of the pancreas and what do they form from? What do they extend into?
dorsal bud forms from the duodenum and extends into the dorsal mesentery (greater omentum).
ventral bud forms from the common bile duct and extends into the ventral mesentery.
Where does the main Duct of Wirsung go?
The main duct of Wirsung extends from the tail and body of the pancreas, (which are formed by the dorsal bud), and extends through the head of the pancreas (which is derived from both the dorsal and ventral buds) into the uncinate process (derived from the ventral bud) to the common bile duct
When the stomach rotates, where does the ventral bud go?
To the right
What do the cells of acni and islets of Langerhans do?
• cells of the acini that secrete digestive enzymes and the adjacent pancreatic islands
• islets of Langerhans that produce insulin (beta cells) and glucagon (alpha cells).
What is the midgut loop connecting the midgut and yolk sac originally tethered by?
• connection with the yolk stalk that subsequently undergoes degeneration,
• superior mesenteric and umbilical arteries
What forms the umbilical hernia?
The descent of the stomach pushes the midgut loop outward into the base of the umbilical cord to form the umbilical hernia
What happens to the midgut when the duodenum elongates and rotates?
90 degree, counterclockwise rotation
What are the two limbs of the midgut? What do they give rise to?
The cranial limb gives rise to the duodenum, jejunum and cranial portion of the ileum (small intestine).
The caudal limb gives rise to the caudal portion of the ileum, and the proximal part of the large intestine, including the ascending and proximal half of the transverse colon.
What arises from the cecal diverticulum?
cecum and appendix
Describe the return of the midgut loop? How many degrees does the midgut turn ccw?
The midgut loop returns in a highly coordinated fashion in a proximodistal sequence.
The proximal limb including the duodenum and the jejunum moves inferiorly and to the left, below the superior mesenteric artery rotating a further 90 degrees counterclockwise around that latter structure, when viewed externally from the anterior (ventral) surface,. As the caudal limb returns it swings a further 90 degrees counterclockwise, when viewed externally from the anterior (ventral) surface; thus, the midgut loop has rotated a total of 270 degrees in the counterclockwise direction.
Where does the hindgut terminate?
cloaca, a blind pocket
What does the cloacal membrane separate?
cloaca from the amniotic cavity and the future anus
What does the hindgut give rise to?
the distal part of the transverse colon, the descending and sigmoid colons and the rectum, the superior/proximal portion of the anal canal and the epithelium of the urinary bladder and most of the urethra.
What does the greater omentum fuse with? What are the two components derived from?
left surface of the greater omentum (from splanchnic mesoderm) fuses with the left, dorsal body wall (from somatic mesoderm)
What are the 2 ligaments of the dorsal mesentary? What are the 2 ligaments of the ventral mesentary? What do they connect?
lienorenal or splenorenal ligament-attached to the spleen is called the gastrosplenic ligament- extends between the spleen and the stomach

hepatogastric ligament- separates stomach and liver
falciform ligament- anchors liver to ventral body wall
What is the lesser omentum? What is it comprised of?
fold in the ventral mesentery between the foregut and the liver

hepatogastric and hepatoduodenal ligaments of the ventral mesentery
What happens during fusion of the mesentaries?
Small intestines attach to posterior body wall via dorsal mesentery. The surfaces of the greater omentum fuse and mesentery of transverse colon fuses to the greater omentum. Splanchnic peritoneum fuses with parietal paritonium. At the same time, the duodenum, head of pancreas, and colons become retro-peritoneal.
How does the allantois form? What lies between the allantois and the yolk sac? What happens to that tissue?
The allantois forms as a diverticulum from the yolk sac that extends into the connecting stalk.

uro-rectal septum

partitions the digestive tract (anorectal canal) from the urogenital/ventral sinus. The septum fuses w/ the cloacal membrane, separating the anal membrane from the urogenital membrane.
The proximal 2/3 of the adult anal canal is lined with hindgut endoderm, while the distal 1/3 is lined with ectoderm. What separates them?
Pectinate Line
What route does the pectinate line show?
development of cancer
What is Omphalocele? What is gastroschisis? What can be done?
incomplete return of the midgut loop from the umbilical cord, causes intestinal hernia

herniated intestines uncovered by any body wall of umbilical tissues, peritoneum or amnion caused by incomplete closure of the lateral folds and rectus abdominis

Surgery
How does an anulate pancreas arise?
a bifid ventral bud may fuse with the dorsal bud around both the dorsal and ventral sides of the duodenum. This leads to duodenum obstruction.
What is an accessory pancreatic duct of Santorini?
leads from the pancreas to the duodenum
What is a Meckel's Diverticulum? What the complication?
proximal part of the yolk stalk that did not undergo normal degeneration

generally okay, but may become inflamed or form an ulcer if ectopic gastric tissue forms in this structure
What is an umbilical fistula?
external opening to the umbilicus persisting after birth
What is a volvulus? What are the complications?
abnormally twisted and constricted intestines and mesentery

may be asymptomatic or the circulation may become obstructed leading to necrosis and gangrene. For instance, the blood supply, via the superior mesenteric artery, may be obstructed.
What is the other name for aganglionic megacolon?
What causes it?
What are the signs after birth?
Hirschsprung’s disease

failure of migration of neural crest cells to form the myenteric plexus in the sigmoid colon and rectum.

enlarged colon and rectum and abdominal distention, due to failure of peristalsis and abnormal fecal retention.
What is recanalization? What problems may occur?
Intestinal endothelial lining proliferates, occluding lumen. Recanalization (cell rearrangement and apoptosis) reopens them.
stenosis or atresia in the esophagus, bile ducts, or small and large intestines. Sometimes a duplicated lumen may develop, leading to the splitting or duplication of the intestines.
How does a persistent cloaca form? What else can occur? How do you solve them?
The urorectal septum fails to fuse with the cloacal membrane, leaving a persistent cloaca and a shared opening of the urethra and the rectum.

A fistula may form that connects the rectum to the perineum, the vagina or the urethra.

surgically.
What happens is the urorectal septum fuses in a more dorsal location?
anal stenosis, anal agenesis, anal-rectal agenesis or anal-rectal atresia.
A fistula can connect the rectum to what 3 things?
perineum, the vagina or the urethra.
What do external excretory structures arise from?
paired urogenital ridges within the intermediate mesoderm and cloaca
What arises from the paired urogenital ridges?
kidneys
What arises from the cloaca?
urogenital sinus, bladder, rectum and anus
What is are the three sets of kidneys that form?
Pronephros, Mesonephros, and Metanephros
How does the Pronephros form? What does it do?
During the process of development, the nephrogenic cords form sequential, segmental nephrotomes, which hollow out as a string of small vesicles. 7 to 10 of these arise in the cervical region to form the pronephros.

Makes a little urine, but largely nonfunctional
How does the mesonephric duct (Wolffian Duct) form?
nephrotomes give off small pronephric ducts that travels through the urogenital ridge and these fuse to form a duct that passes to the cloaca, this duct becomes the mesonephric duct.
What does the Wolffian Duct form?
metanephric diverticula and the ureter and persists in the male as the vas deferens
What is the function of the mesonephric (Wolffian) duct?
3 things:
Helps develop kidneys.

All 3 kidneys empty via the mesonephric ducts.

fuses with the dorsal surface of the cloaca of the hindgut, which will ultimately be partitioned to form the bladder and part of the urethra.
Through which ducts are gametes released from gonads?
males- the Wolffian ducts or vas/ductus deferens

femaile- paramesonephric duct
What does the paramesonpehric duct form?
Müllerian ducts or uterine or fallopian tubes, and the uterus and proximal vagina
How do the nephrons form?
After the initial formation of the pronephros, the mesonephric vesicles form and their tubules also fuse with the mesonephric ducts (weeks 5-9). The individual nephrotomes give rise to the mesonephric vesicles that form individual functional units of the mesonephros, the nephrons.
What forms the mesonephric tubule?
nephrons of the mesonephros
What transports sperm to the Wolffian Duct (vas deferens or mesonephric)?
What is this structure made from?
ductuli efferentes

mesonephric tubules
What forms the metanephros?
paired ureteric buds( also known as metanephric diverticulum) (derived from the mesonephric ducts) and the surrounding metanephric mesoderm
What does the metanephric diverticula form?
The metanephric diverticula form the ureter, renal pelvis, calices and collecting tubules
What gives rise to major and minor calices?
Ureteric buds
What gives rise to the ureteric buds?
mesonephric ducts?
What gives rise to a renal lobe containing a renal pyramid?
major calice
What is at the tips of the straight and arched collecting tubes?
At the tips of each straight collecting tubule form arched collecting tubules. At the tips of the arched collecting tubules the mesoderm of the interacting metanephric blastema forms a vesicle.
How is the process of nephron development different for metanephros?
it is branching growth and involves 2 types of mesoderm
What is derived from metanephric blastema?
nephrons
Which nephrons are older? (hint: renal pelivs position)
Those lying closer to the renal pelvis (oldest nephrons) are more advanced and have a longer Henle’s loop.
When does the last nephron form?
Sometime before birth. No nephrons form after birth.
The hylum of the kidneys goes from ventral to _____________?
directed at the midline
What 4 things are bundled inside a mature nephron?
bowman’s capsule, proximal convoluted tubule, Henle’s loop and distal convoluted tubule
Describe the movement of the kidneys
The kidneys begin their development in the pelvis and ascend anteriorly (superiorly) and later become attached to the posterior body wall in the abdomen (they become stabilized and are retroperitoneal).
Do the renal arteries and veins elongate during ascension?
No new connections are formed from the aorta.
What maintains its original arterial connections?
gonads
What do suprarenal and adrenal glands derived from?
mesoderm and neural crest cell derivatives
What gives rise to the primary fetal cortex? What gives rise to the medulla?
mesenchymal cells
neural crest cell derivatives
How do ganglionic cells sort out?
Differential adhesion
How is the bladder formed?
subdivision of the cloaca, via the urorectal septum, which splits the hindgut into the urogenital sinus and the rectum
What 3 parts does the ventrally located urogenital sinus have?
the vesical, the pelvic and the phallic
What does the allantois degenerate to form?
urachus or the median umbilical ligament
What forms the trigone?
The portion of the duct common to both the ureter and the urethra is absorbed into the outer surface of the bladder on the dorsal side, and forms the mesodermal trigone
How does the mesonephric duct differ between males and females?
In the male the mesonephric duct persists as the ductus or vas deferens and enters the urethra as the ejaculatory duct, but these structures degenerate in the female.
What causes renal agenesis?
failure of development of ureteric buds
What leads to bilateral or unilateral kidney?
no induction of the mesonephric duct by the metanephric blastema
What is a consequence of Bilateral renal agenesis (Potter’s syndrome)?
oligohydramnios
What are double kidneys?
The ureteric buds may continue to divide generating a supernumerary ureter. Likewise it is possible that bifid or supernumerary kidneys may also form from separate ureteric buds. The lobes of the developing kidneys may also be more pronounced, or there may be division of the kidneys (e.g., partial or completely separated, double kidneys).
What causes a flat kidney?
fusing at the level of the bladder
The fusion event prevents ascent by trapping the kidney beneath the inferior mesenteric artery.
Can the kidneys both end up on one side of the body?
Yes
What causes polycystic kidney and what can treat it?
Old vessels obstruct the ureter.
What ectopic sites can ureters fuse with bladder?
neck of the bladder, genital duct or prostatic urethra in males or with the neck of the bladder or vestibule of the vagina in females
Where does the ureter normally connect to the bladder?
At the vesical part
What occurs during extrophy of the bladder? How do you solve this?
Normally the lateral folds close and mesenchyme migrates to the ventral midline to form ventral body wall structures (e.g., muscles) located between the bladder and the fused surface ectoderm. Should these fail to undergo normal development, the midline may remain open or weakened. Persistent openings will reveal the mucosa of the bladder.

Surgery
How do you get epispadia?
In males, problems related to fusion of the lateral folds may lead to a split, exposed urethral groove on the upper or “dorsal surface” of the penis (called epispadia).
How do you get a urachal fistula or cyst?
Normally, the allantois degenerates, however, urachal cysts, sinuses or an open fistula may persist. Isolated fluid filled urachal cysts may remain in the body or an open passage may remain (urachal fistula) that allows urine to escape through the umbilicus.
Where are PGCs initially located? Where do they migrate? How do they travel and what do they pass by during migration?
endodermal (hypoblast) layer of the secondary yolk sac near the allantois

gonadal (genital) ridges

along the hindgut and through the dorsal mesentery
When the PGCs are in the gonadal anlage, what are they called?
spermatogonia and oogonia
Where do gonads begin their development?
medial surface of the urogenital ridge in close proximity to the developing mesonephros
What does PGCs stimulate the growth of?
gonads
These ducts form initially as an invaginated groove within the mesothelium of the urogenital ridges by induction from the adjacent mesonephric ducts
paramesonephric
What forms when the paramesonephric duct fuses with the urogenital sinus?
uterovaginal primordium
What forms sex cords?
mesothelium
The gonads take on an ovoid shape and attach to the dorsal wall via what mesentery?
urogenital mesentery, which is called the mesorchium in the male and the mesovarium in the female.
In the male, the PGCs are incorporated into the primary sex cords and they become the testes cords, but what happens in the female?
Female primary sex cords degenerates. Secondary sex cord forms.
How does the tunica albuginea form?
Mesoderm proliferates into the space located between the developing primary sex cords (which now reside in the medulla), and the outer mesothelium that covers the developing gonads. These cells forms a thick layer of white extracellular matrix and connective tissue called the tunica albuginea.
What the tunica albuginea isolate?
This tissue isolates the primary sex cords away from the outer cortex. Hence, sperm cells effectively complete their maturation within in the medulla of the testis
What stops the formation of secondary sex cords in males?
tunica albuginea
What does the testis cords and rete cords lie close to respectively?
The testis cords lie closer to the mesothelium and the rete cords lie deeper and closer to Bowman’s capsules of the mesonephric tubules
What connects the rete testis to the mesonephric duct?
vas or ductuli efferentes
What is the epididymis?
region of the mesonephric duct adjacent to the vas efferentia, stores sperm
What forms the seminiferous tubules? What do they contain?
The outer testis cords

spermatogonia and the sustentacular, stromal cells (e.g., Sertoli cells).
What do Sertoli cells do?
secrete Müllerian inhibiting substances (MIS)
What family is Anti-Mullerian Hormone part of?
What does Anti-Mullerian Hormone do?
TGF-beta family of secreted growth factors.

stimulates degeneration of the paramesonephric ducts in the male and sustains the development of the mesonephric ducts.
What do Leydig cells do?
synthesize the androgenic hormones, testosterone, and dihydrotestosterone, which stimulate male development of the mesonephric duct and the external genitalia.
What stimulates production of androgenic hormones, testosterone, and dihydrotestosterone?
hCG (initially secreted by the placenta between weeks 8-18) and subsequently by fetal pituitary gonadotropins.
What are the 2 remnants of the paramesophrenic duct?
prostatic utrical
appendix testis
What are the progenitors of the appendix of the epididymis and the paradidymis?
mesonephric duct

paragenital tubules
What happens to primary sex cords in women?
The primary sex cords mainly degenerate in the female. Vascular tissue replaces the degenerated outer cords, and the inner cords give rise to the vestigial rete ovarii, which are non-functional, vestiges of these structures.
Why is the tunica albuginea delayed in women?
the secondary sex cords can form
How do the primary oocytes arise? Where do oocytes mature?
These secondary cortical cords ultimately receive the oogonia, which form clusters of cells giving rise to the primary oocytes, which are surrounded by follicle cells.

oocytes mature in tissue derived from the cortex of the ovaries.
In the absence of _____ and ________, the paramesophrenic duct is maintained?
What makes paramesonephric ducts give rise to the uterine tubes and the ostium or infundibulum ?
AMH and testosterone
Estrogen
What creates the broad ligament?
Fusion of the paramesonephric ducts joins the peritoneal folds of the mesovarium and produces the “broad ligament.”
What gives rise to the uterovaginal primordium? What does this give rise to?
caudal ends of the paramesonephric ducts fuse and join the posterior side of the urogenital sinus

uterus and proximal 1/3 of vagina
What does the uterovaginal primordium form?
The uterovaginal primordium forms the uterus and the proximal third of the vagina.
The inferior 2/3 of the vagina form?
The point where the uterovaginal primordium contacts the urogenital sinus induces the formation of the paired sinovaginal bulbs. Together these form the vaginal plate. The vaginal plate continues to grow and gives rise to the inferior two-thirds of the vagina.
What are the components of the broad ligament?
This includes the suspensory ligament of the ovary, and the remnants of the gubernaculum, as the ligament of the ovary proper, and the round ligament that passes through the inguinal canal. The gubernaculum represents a ligamentous structure derived from the mesovarium (or mesorchium in the male) that runs from the caudal end of each gonad to each of the labioscrotal folds. The mesosalpinx represents the part of the broad ligament that encloses the uterine tube and that extends from the ligament of the ovary.
What are the remnants of proximal mesonephric tubules? What are the remnants of the mesonephric duct?
What do the more distal tubules remain as? What is the remnants of their duct?
epoophoron
the duct of the epoophoron
paroophoron
Gärtner’s duct or cyst.
What drives the descent of the gonads?
The elongation of the body and the shortening of the gubernaculum
What do the testes descend towards and were do they end up?
labioscrotal folds

processus vaginalis/scrotum
What is the tunica vaginalis?
cavity (potential space) along the ventral side of the testes. The space allows for free movement of the testes (controlled by muscular contraction) and is important for normal temperature regulation and optimal sperm production in these structures.
What divides the cloacal membrane into the urogenital membrane and the anal membrane?
Fusion with urorectal septum
The genital tubercle ultimately becomes ____ or ________?
glans clitoris or glans phallus (glans penis)
What does the labioscrotal swelling become?
scrotum or labia majora
What do the urogenital folds become?
fuse --> shaft of penis or remain open --> labia minora
If the urethral groove remains open, what forms? What happens in males?
Vestibule of the vagina

penile urethra
Dihydrotestosterone is important for the development of what 3 male structures? What requires testosterone?
Penis, scrotum, and prostrate
Vas deferens, epididymis, and seminal vesicle
What gives rise to the prostate? What are the female equivalents?
urethral endothelium

Urethral and paraurethral glands of skene
What are the 2 specific cases involving SRY and DSS that cause gender reversal?
SRY on X --> XX male

2x DSS on X --> XY female
What are the 2 chromosomal diseases?
Turner’s syndrome (XO)- ovarian hypoplasia) and ambiguous external genitalia.
Klinefelter’s males (trisomy XXY)- reduced testicular size and enlarged breasts related to a decrease in androgens and an increase in gonadotropins.
What is cryptoorchidism? What are the problems and what is the treatment?
testes trapped in (more commonly) or at the openings of the inguinal canal, or may fail to fully descend in the scrotum.

If the testes remain inside the body or fail to fully descend into the scrotum, they will not produce viable sperm and may undergo degeneration. In these cases there is an increased risk of occurrence of malignant tumors, and the testis should be relocated (orciopexy) or removed (orchectomy).
Why does an inguinal hernia occur? What is an inguinal hernia? What does this lead to? Life threatening?
processus vaginalis fails to close in a male

portion of the intestines extend into the tunica vaginalis or to formation of a fluid filled swelling or hydrocele of the tunica vaginalis.

strangulated bowel

Yes
How do bicornate and unicornate uterus development?
If the septum that initially separates the fused paramesonephric ducts fails to degenerate, a bicornate uterus will result. In some cases there may be a failure in the development of one half and this results in a single-sided, unicornate uterus.
How do vaginal atresia and agenesis occur?
Failure of induction of the uterovaginal primordial, to form the vaginal plate (sinovaginal bulbs) will lead to the absence of the vagina (Vaginal atresia). Other forms of vaginal agenesis also can occur leading to the presence of a persistent urogenital sinus and opening.
How do you develop hypoplasia?
The urethral opening may be located abnormally on the ventral surface of the penis, as in the case of hypospadias (which effects 1/500 boys). This condition is related to incomplete fusion of the urogenital folds.
Why do male psuedohermaphrodites develop? What should we do?

Why do female psuedohermaphrodites develop?
Androgen Insensitivity Syndrome (don't respond to testosterone), lack of testosterone, and lack of AMF
REMOVE TESTES, MAY BE MALIGNANT

This condition is related to mutations in the genes encoding enzymes involved in adrenocortical steroid production (21-hydroxylase or 11-beta-hydroxylase). As cortisol is not produced, the negative feedback on the pituitary is removed and ACTH is produced in high quantities. This in turn stimulates the adrenal cortex and results in congenital adrenal hyperplasia and increased synthesis of androgens. Other problems are associated with this condition (e.g., salt imbalances). Treatment involves steroid hormone replacement therapy (using cotisol and mineralocorticoids).
Where does the branchial (pharyngeal) apparatus form?
forgeut
How many arches are in the pharyngeal apparatus? How many are externally visible? Why?
6
4
#5 degenerates and #6 is more internal and less prominent
What 3 things do the pharyngeal arches contain? What 4 structures are between arches?
• the aortic arches (from mesenchyme)
• cartilaginous support elements (from neural crest)
• specific cranial nerves and muscles (from CNS and epibranchial placodes)

pharyngeal pouches
What is the other name of the 1st arch? What can the arch be split into?
What type of cartilage is inside? What does that cartilage become?
mandibular arch

maxillary prominence (forming the upper lip, maxilla and palate) and the mandibular prominence (forming the lower lip and mandible)

Meckel’s cartilage
incus and malleus and core of the mandible
What is the other name for the 2nd arch? What type of cartilage does it contain? What does that cartilage become?
2nd arch- hyoid arch, and contains

Reichert’s cartilage

Reichert’s cartilage becomes
• styloid process
• part of the Hyoid bone (also derived from neural crest of the third arch)
• the third auditory ossicle, the stapes.
• lesser cornu
Where does Rathke's Pouch form? How does the pituitary form?
The ectodermal, hypophysial diverticulum or Rathke’s pouch forms in the dorsal roof of the stomodeum in the region anterior to the first arch and meets the infundibulum, a ventral midline evagination of the forebrain (from the ventral, floor of the diencephalon).

Rathke’s pouch (hypophysial diverticulum) + infundibulum = pituitary (hypophysis)
What are the 2 lobes of the pituitary and what do they do?
Pituitary consisters of anterior (adenohypophysis) and posterior (neurophypophysis) pituitary lobes

The anterior pituitary (adenohypophysis) serves as an endocrine organ:
• secreting growth hormone
• corticotropin
• luteinizing hormone
• follicle stimulating hormone
The posterior pituitary serves as a neuronal interface with the anterior pituitary and also releases various hormones, including oxytocin and vasopressin.
What gives rise to the tongue? What parts of the tongue do they form?
ventral region of the first, third and fourth pharyngeal arches

1st arch - tongue buds (oral part)
3rd and 4th arches- proximal or pharyngeal part (hypobranchial eminence)
How is hormone production regulated?
Hormone production is regulated by the hypothalamus via neural activity (to control the posterior lobe) and via releasing and inhibiting factors (to control the anterior lobe).
How do the arches overgrow each other in the tongue?
At the midline, arch 3 overgrows arch 2 in a cranial direction, and arch 4 overgrows arch 6 in the caudal direction.
What is the epiglottis derived from? What is the larynx derived from?
The epiglottis is derived from the inferior end of the hypobranchial eminence in the fourth arch. Mesenchyme derived from the fourth and sixth arches proliferates to form the bilateral arytenoid swellings of the glottis, which form the laryngeal cartilages.
How does the thyroid gland form (what arch)?
What leads to the thyroglossal duct and thyroid diverticulum?
How does the developing thyroid move?
A small evagination forms just proximal to the median tongue bud in the region of the second arches (just inferior to the median tongue bud)

foramen cecum

The developing thyroid ultimately descends in the neck to its normal location inferior to the level of the larynx.
What's a precursor to neurocranium and viscerocranium? What are they?
neural crest cells of the branchial arches
neurocranium- encloses the brain and the viscerocranium- forms the skeleton of the face.
What cartilage does the third arch and the 4th/6th arches form?
The third arch cartilage- greater cornu (horn) and inferior part of the body of the hyoid bone.
The fourth and sixth arches- thyroid and cricoid cartilages
What are the muscles of the tongue derived from?
What muscles do the 1st and 2nd arches form?
somites in the occipital region (the occipital myotomes)

Cells of the first arch make the muscles of mastication, e.g., masseter, mylohyoid and temporalis muscles. Those of the second arch make the muscles of facial expression.
Match the following nerves with their innervations:
trigeminal nerve (V, maxillary and mandibular divisions)
facial nerve (VII)
glossopharyngeal nerve
vagus nerve
accessory nerve
cranial nerve XII (hypoglossal nerve)
trigeminal nerve (V, maxillary and mandibular divisions) first arch, face lining of mouth
facial nerve (VII) second arch
glossopharyngeal nerve third arch, pharynx, and esophagus
vagus nerve fourth and sixth arch, pharynx, esophagus
accessory nerve sternocleidomastoid and trapezius muscles
cranial nerve XII (hypoglossal nerve) muscle of the tongue
How are the branchial sinuses formed?
the 2nd and 6th
arches overgrow the
3rd and 4th
&
create the cervical sinus,
which is subsequently
obliterated
What are pharyngeal grooves and pouches?
pharyngeal grooves represent external grooves located between adjacent arches. The pharyngeal pouches represent corresponding internal pockets of endoderm that extend between the adjacent arches
What are the derivatives of the pharyngeal pouches,
branchial grooves, and membranes?
The external auditory meatus forms between the first and second arches in the first branchial groove. The auditory tube (eustachian tube) is derived from the first pharyngeal pouch, and the tympanic membrane is derived from the first pharyngeal membrane. The palatine tonsils form in conjunction with the second pharyngeal pouches. The inferior parathyroid gland and thymus gland (involved in the production of thymic hormones and mature T lymphocytes, or thymocytes) are formed from the third pharyngeal pouches. The superior parathyroid gland and the ultimobranchial body ( or ultimopharyngeal body, contains C cells derived from migrating neural crest that produce calcitonin and are involved in Ca++ regulation) is derived form the fourth pharyngeal pouches. These derivatives of the third and fourth pharyngeal pouches migrate inferiorly to reach their definitive adult positions within the neck. The thymus, and inferior parathyroid gland (derived form the third pharyngeal pouches ) actually come to lie inferior to structures derived from the fourth pouch (e.g., superior parathyroid and ultimobranchial body). The thymus actually grows inferiorly into the thorax.
What are the 5 mesenchymal condensations what make up the face?
medial frontonasal prominence located superior to the stomodeum, as well as two initially paired, bilateral maxillary and two mandibular prominences
What is the source of facial mesenchyme?
neural crest cells
What contributes to the formation of the upper lip and maxilla?
fusion of the maxillary prominences along the ventral (frontal) midline with the intermaxillary segment derived from the frontal prominence
What contributes to the formation of the lower lip and jaw?
mandibular prominences, located caudal to the stomodeum, fuse
Where do the nasal placodes form?
Within the frontonasal prominence
What forms the nasal or olfactory pits and nasal sacs? What binds the nasal sacs?
nasal placodes
median and lateral nasal prominences
What happens at the same time the nasal pits move and where do they go?
The medial prominences fuse to form the intermaxillary segment

inferiorly, to a frontal, medial location on the face
Where does the otic placode being its formation and where does it migrate?
dorsal to 2nd pharyngeal arch, 1st branchial groove
What do the 6 auricular hillocks surround and what do they form?
They surround the external auditory meadis

external auricle
Where do the eyes develop? Where do they move?
laterally within the head at the junction between the frontonasal prominence and the maxillary prominences

anteriorly to the frontal surface of the face
What is the epithelial lining of the outh and nasal cavities derived from?
ectodermal invagination of the stomodeum and olfactory placodes
What part of the nasal sacs degenerate and becomes continuous with what?
floor
oral cavity
Where does olfactory epilthelium form?
roof of nasal sac
What are olfactory sensory neurons derived from?
ectoderm of the nasal sac
Where does the nasal septum start and what does it separate?
intermaxillary segment
left/right sides of nasal cavity
Where des nasal conchae and turbinate form?
lateral walls of the 2 nasal cavities

within the conchae
What is the palate a fusion of? What direction does fusion occur?
median palantine process --> primary palate
lateral palatine process --> secondary palate
Nasal septum --> roof of the nasal cavity
uvula

ventral to dorsal
What forms the hard palate? What forms the soft palae and uvula? What is the incisive foramen?
The primary palate and anterior 2/3 of the secondary palate

The soft palate and uvula are derived from the posterior 1/3 of the secondary palate.

Within the hard plate the incisive foramen represents the posterior most extent of the primary palate at the junction of the primary palate and two lateral palatine processes (secondary palate).
What causes cleft lip and/or palate?

What causes cleft lip?
What causes median cleft lip?
What causes oblique cleft lip?
What causes median cleft of the lower lip?
What causes macrostomia?
What causes microstomia?
cleft lip- abnormal, incomplete fusion of the maxillary prominences with the intermaxillary segment.

median cleft lip- incomplete fusion of the median nasal prominences.

oblique cleft lip- Incomplete fusion of the lateral nasal prominence with the maxillary prominence.

median cleft of the lower lip- Incomplete fusion of the two mandibular prominences.

Macrostomia (big mouth)- incomplete lateral fusion results in
microstomia- excessive fusion between the maxillary and mandibular prominences
What is anterior cleft plate? What is a posterior cleft palate? What is an anteroposterior cleft palate? What is a soft palate cleft classified?
Anterior cleft palate- primary palate fails to fuse with the lateral palatine processes (shelves).
Posterior cleft palate- lateral palatine processes (shelves) fail to fuse with one another and with the nasal septum.
anteroposterior cleft palate- combination of above.
All cleft palates involving strictly the soft palate are included in the posterior classification.
What causes 1st Arch Syndromes? What are 2 examples? How do you corrected them?
abnormal migration of neural crest cells to the first pharyngeal arch

Treacher Collins syndrome- underdevelopment of the zygomatic bones, mandible, and ears with possible narrow or obstructed airway

Pierre-Robin Syndrome- mandibular hypoplasia and often obstructed airway

Both surgery correctible
What is plapebral coloboma and eyelid coloboma?
condition in which the upper (more commonly) or lower eyelid develops abnormally. The latter, though rare, is a condition found in association with first arch syndrome (e.g., Treacher Collins syndrome)
What causes and what is DiGeorge Syndrome?
Deletion in chromosome 22 --> abnormal neural crest development and abnormal development of the third and fourth pharyngeal pouches --> CV defects, immunodeficiency, and hypocalcemia + facial defects
What is ankyloglossia?
the frenulum of the tongue extends abnormally to the tip of the tongue, thus preventing its normal protrusion from the mouth.
What sort of cysts and fistula develop in the neck and head region?
Under abnormal conditions a branchial or pharyngeal cyst may remain that represents a persistent opening of the branchial grooves (2, 3, or 4) or branchial sinus (typically located near the angle of the mandible). Likewise a pharyngeal fistula may form that represents an open communication between the tonsillar sinus within the neck and an external opening on the side of the neck (e.g., persistent branchial sinus). These passages may become infected.
What does persistent remnants of the thyroglossal duct form?
thyroglossal cysts, which may be visibly protrude from the neck externally (more common) or be located closer to the base of the tongue (i.e., Lingual cyst) within the pharynx. They may lie dormant for years, but problems generally occur before age 20. These cysts are rare but they may become enlarge and infected, requiring fluid aspiration, antibiotics and possibly surgery, should the problem persist.
What does persistent remnants of Rathke's pouch for? What treatment is here?
congenital benign tumor, Craniopharyngioma  visual loss (due to the close proximity of the optic chiasm), and endocrine disorders. Treatment: surgery, maybe radiation therapy, and hormone replacement therapy.
What causes congenital hypothyroidism? What does it lead to? What is treatment?
maternal thyroid deficiency early during the fetal period, fetal thyroid deficiency later during pregnancy, or lack of iodine.
Likewise, this may be related to thyroid agenesis or specific genetic mutations affecting the biosynthesis of thyroid hormone.
defects in skeletal growth, dry-rough skin, wide-set eyes, periorbital puffiness, a flat broad nose, and an enlarged protruding tongue.
If untreated, it leads to mental retardation and dwarfism.
Treatment involves thyroid hormone replacement therapy.
What does the viscerocranium arise from?
cartilaginous models derived from 1st and 2nd pharyngeal arches
squamous temporal, mandible, parts of maxilary, zygomatic bones
What does the neurocranium consist of?
(1) the base of the skull, or cartilaginous neurocranium (also called the chondrocranium, which develops in part from prechordal plate mesoderm

(2) the thin flattened bones (plates) of the calvaria (the membranous neurocranium or cranial vault).
Where do bones of the basal plate develop and encircle?
The bones comprising the basal plate that develops around the cranial end of the notochord and encircle the foramen magnum represent the cartilaginous neurocranium.
What makes up the cartilaginous neurocranium?
inferior part of the occipital bone, petrous temporal bone, ethmoid and sphenoid bones.
What is the membranous neurocranium made up? How do they form? What are they derived from? What happens to them?
The membranous neurocranium is represented by the bones of the calvaria (the thin flattened plates that includes the frontal, parietal, and superior part of the occipital bone). These bones form through intermembranous ossification without a cartilaginous model. Ossification of boney spicules spreads from primary ossification centers that fuse after birth. These plates are derived from neural crest and dermatome that form dermal bone. The bones of the calvaria ultimately fuse with those of the basal plate.
What are sutures? What are the prominent suture? What are the junctions between the bones? Where is the soft spot? When does it form and they it is important?
The initially membranous connective tissue junctions between two adjacent bones of the neurocranium are referred to as sutures. Prominent sutures of the neurocranium includes the sagittal, coronal , frontal and lambdoid sutures. The junctions between three or four bones are referred to as the fontanelles. There are six fontanelles (1 anterior, 1 posterior, 2 anterolateral and 2 posterolateral) in the neurocranium. The prominent anterior fontanelle located on the top of the head of a newborn (e.g., the “arrowhead” located at the anterior end of the sagittal suture; “sagitta” = “arrow”) is commonly called the “soft spot”. The soft spot has generally completed ossification by 12-14 months of age. The presence of the sutures and fontanelles is important to allow for proper growth and expansion of the skull and brain. They also provide for flexibility of the skull as it passes through the birth canal.
Describe the organization of the neural tube and spinal cord
developing neural tube and spinal cord with an inner, ventricular layer (where mitosis occurs), an intermediate or mantle layer (containing cell bodies of differentiated descendants, which gives rise to the grey mater) and an outer marginal zone (with neurites or axonal projections that represents the white mater)
What is the brain derived from? What are the 3 principal brain vesicles?
The brain is derived from the more anterior part of the neural tube

forebrain, (prosencephalon), the midbrain (mesencephalon) and the hindbrain (rhombencephalon)
Why does the brain inflate? Why is this pressure necessary?
By the sixth week of development the forebrain is inflated by increased internal pressure caused by the production of the cerebral spinal fluid (CSF), by the choroid plexus. This increased pressure is necessary for normal development of the brain, as evidenced by experiments performed in other vertebrates, including chicken embryos, in which a cannula was inserted to drain CSF.
What elongates faster, the neural tube or the rest of the body?
neural tube
Where do flexures form?
, one anterior flexure forms at the level of the midbrain, (the so-called midbrain or cephalic flexure), and a second posterior flexure forms between the hindbrain and the spinal cord (the cervical flexure)
What forms the cerebral hemispheres?
What makes up the telencephalon?
cerebral vesicles
paired cerebral hemispheres and anterior end of neural tube
What is the more posterior region of the forebrain? What does that give rise to? What protrudes from the sides of that posterior region?
diencephalon
epithalamus, thalamus, and hypothalamus

optic veiscles
What does the hindbrain or rhombencephalon form?
rhombomeres
What does formation of the pontine flexure do? What is the region anterior to the pontine flexure called? What does it form? What is the region caudal to that? What does that give rise to?
flattens the neural tube and thins the dorsal surface

metencephalon
cerebellum and pons

myelencephalon
medulla oblongata
Where does the 4 cranial ganglia? What are they derived from?
What do nerves do they give rise to in the branchial arches?
Adjacent to the hindbrain, between the midbrain and cervical flexures
neural crest
first arch contains the trigeminal nerve (V), the second arch contains the facial nerve (VII), the third arch contains the glossopharyngeal nerve (IX), and the fourth arch contains the vagus nerve (X).
What separates the dorsal, afferent, alar and ventral, efferent, basal plates? What separates the bilateral left and right halves of the brain dorsally and ventrally?
sulcus limitans
dorsally- roof plate
ventrally- floor plate
Explain the open book view of the rostral hindbrain.
In the rostral part of the hindbrain, the developing brain resembles an “open book” with a highly-expanded, thin, dorsal roof plate. The more thickened (ventral) regions contain the alar and basal plates (“open cover and pages of the book”), united ventrally by the floor plate, which is essentially resembles the “spine of the open book.”
What forms the tela choroidea? Where is it? What is the name of its vascularized branching organs?
ependyma, pia and arachnoid matter,

roof plate

choroid plexus
What are in the nuclei in the hindbrain and midbrain composed of? How are they arranged? Going dorsal to ventral, list the nuclei.
somatic and visceral neurons, and glia

columns which represent extensions of horns of spinal gray matter

somatic afferent, visceral, and somatic efferent nuclei
What visceral nuclei located nearest to the sulcus limitans supply the viscera of the trunk?

What nuclei flank the visceral nuclei and supply structures derived from the pharyngeal arches?
GVE and GVA

SVE and SVA
Which nuclei located in the basal plate represent extension of the lateral horn in the spinal cord as well as supply skeletal muscles derived from somitic myotomes or the paraxial mesoderm?

Which somatic nuclei located in the alar plate receive sensory input from various receptors and the special sense, respectively?
SE or GSE

GSA and SSA
How do mantle nuclei communicate with the body?
cranial nerves
What nerves are classified as nerves of the pharyngeal arches? These are mixed nerves, what does that mean?
trigeminal, V, Facial, VII, Glossopharyngeal, IX, Vagus, X, and Accessory, XI

containing both efferents and sensory fibers from neural crest derivatives
What is odd about the accessory nerve?
Note that the accessory nerve (XI) contains efferent fibers, but has two sets of efferent contributions (spinal and cranial). Though technically not a nerve of the pharyngeal arches, the spinal part of the accessory nerve (XI) is derived form cervical spinal nerves and supplies the sternocleidomastoid and trapezius muscles (the cranial part supplies muscles of the palate and larynx)
List the somatic efferent cranial nerves and what they serve?
oculomotor (III), the trochlear (IV), the abducens (VI), and hypoglossal nerve (XII). The oculomotor, trochlear and abducens nerves serve muscles of the eye. Although they are classified as somatic efferent nerves, CN, III, IV and VI also carry fibers of proprioreceptive nerves that serve the eye muscles. CN III also contains parasympathetic neurons. The hypoglossal nerve (XII) serves the muscle of the tongue.
What are the special sensory nerves? Where do they arise? What is odd about the optic nerve?
olfactory nerve (I), and the vestibulocochlear nerve (VIII). These cranial nerves are strictly afferent. In these cases the sensory fibers are actually not derived primarily from neural crest cells. Rather they arise from ectodermal placodes (e.g., the olfactory nerve I, from the olfactory placode, and the vestibulocochlear nerve VIII, from the otic placode). These afferent axons extend to SSA nuclei in the brain. Note that the optic nerve (II) is not a true cranial nerve, but rather a tract of the diencephalon, forming via the evagination of the optic vesicle and subsequent development of the optic cup.
How is the hindbrain organized?
The hindbrain (Rhombencephalon) is organized in a segmental fashion as rhombomeres, which are closely associated with the branchial arches. Arch 1 is associated with Rhombomeres 2,3; arch 2 is associated with rhombomeres 4,5; arch 3 and 4 with rhombomeres 6,7,8. Some rhombomeres are associated with specific cranial ganglia.
What are the 2 foramina behind the cerebellum? What do they allow?
Behind the cerebellum, the roof plate of the fourth ventricle possesses open foramina (the paired foramina of Luschka and the single foramen of Magendie (median aperture). These foramina form via programmed cell death, and allow CSF produced in the ventricles to enter the subarachnoid space.
What do the nuclei in the marginal zone arise from? What do the function in? Why marginal nuclei are there?
mantle cells, alar plate

afferent pathways

These include the gracile and cuneate nuclei in the dorsal marginal zone of the medulla. The inferior olivary nuclei at the pontine flexure, and the pontine, cochlear and vestibular nuclei and sensory nuclei of the trigeminal nerve. In the midbrain these include the superior and inferior colliculi, located dorsally in the tectum, and ventrally, the red nuclei and substanitia nigra in the tegmentum (it is unclear whether these ventral nuclei of the midbrain are derived from alar or basal plates).
Where does the cerebellum develop?
What is it derived from?
Explain the change in shape and over time.
rostral hindbrain (metencephalon)

rhombic lip comprised of the alar plate rostral to the pontine flexure

As the pontine flexure forms, and the hindbrain buckles, it assumes a rhombic shape hence the term “rhombencephalon.” By three months of development growth of the hindbrain has brought the rostral and caudal surfaces of the flexure in contact with one another. The rhombic lip begins to straighten out and gives rise to the transverse cerebellar plate with extra- and intraventricular parts located just anterior to the pontine flexure. This configuration resembles the shape of a short flexed rubber tube, which has been slit on one side (dorsally) and pushed together at both ends. With increasing growth, the cerebellar cortex enlarges and folds into transverse grooves that separate the various lobes, including the flocculonodular lobe (archicerebellum at the most-caudal end), the posterior lobe (neocerebellum) and the vermis and anterior lobe (paleocerebelulum). By four months the pontine flexure opens somewhat, and is more shallow. The posterior medullary vellum forms the caudal margin of the cerebellum.
What is the consequence of homozygous (wv/wv) or heterozygous (+/wv) weaver mutant mice?
abnormal development of the Bergmann glial cells, and hence abnormal migration of the granule cells, and the purkinje cells arborize abnormally.
What is the consequence of X-irradiating and destroying granule cells?
you get abnormal migration and arborization of purkinje and golgi type II cells
Describe the formation of the external granular layer.
cells migrate from the rhombic lip of each alar plate along the pial surface to form a second germinal zone called the external granular layer, which lies at the surface in the marginal zone between the purkinje cells and the pia. After week 20 this layer generates neurons that subsequently migrate deeper toward the differentiating purkinje cells. The granule cells form parallel fibers that run in the most superficial layer (molecular layer) and migrate along Bergmann glial cells (tightly associated with Purkinje cells) where their cell bodies come to reside in the internal granular layer.
Where do cells migrate to form the cerebellar cortex?
marginal zone
Where do immature Purkinje and Golgi type II cells migrate from before they enter the cerebellar plate?
the intermediate zone in the roof of the 4th ventricle
Where do basket and stellate cells go?
Basket and stellate cells remain in the molecular layer.
Where do axons of Purkinje cells travel to/from within the cerebellar cortex?
Axons of Purkinje cells pass from the cerebellar cortex and mossy fibers and climbing fibers enter it to/from the white matter of the cerebellum, which is located between the internal granule layer and the ependyma. (This is in contrast to the arrangement found in the spinal cord where axons to and from the grey matter pass through the superficial, marginal zone).
What is Crania bifidum?
Defects in the development of the skull, such as crania bifidum can cause malformations of the brain, analogous to spina bifida cystica. Such defects are often along the median plane, and the brain may herniate through the fontanelles or commonly at the junction with the foramen magnum at the base of the occipital bone. Depending on which tissues are involved, such defects may be classified with meningocele (protrusion of the meninges), with meningoencephalocele (protrusion of the meninges and brain tissues), and with meningohydroencephalocele (protrusion of the meninges, brain and part of a ventricle).
What is Anencephaly (Meroanencephaly) and Acrania?
Anencephaly is a type of neural tube defect resulting when the anterior neuropore fails to close during the fourth week of development. In this case, the brain will not enlarge properly and the developing brain tissue remains exposed to amniotic fluid. This condition causes the brain to develop abnormally. The cranium is greatly reduced or absent, a condition referred to as acrania. Typically much of the forebrain degenerates, although the rudimentary midbrain and hindbrain may remain, a condition referred to as meroanencephaly (partial anencephaly). Polyhydramnios often accompanies anencephaly, as the brain defect prevents the fetus from properly swallowing amniotic fluid. This defect is relatively common (occurring in 1/1000 births) and is always fatal shortly after birth. Such problems can be detected using ultrasonography, beginning at 14 weeks of development.
What is Microcephaly ?
Microcephaly is a condition characterized by abnormal/reduced growth of the cerebrum and cerebellum, but the cranium remains present. The overall size and shape of the face may be normal but the brain and skull are abnormally small. The development of the face is thus dissociated from that of the brain and skull. Growth of the calvaria occurs in response to the pressure of the growing brain.
What is Craniostenosis?
If the plates of the skull fuse prematurely (craniostenosis, e.g., premature ossification at the sutures) brain development may be impaired and subsequent development of the brain may lead to deformation of the calvaria. If the sagittal suture closes prematurely, this leads to the formation of an elongated thin cranium (scaphocephaly, or dolichocephaly, 50% of the cases). If the coronal and/or lambdoid sutures closes on both side prematurely this leads to a high cranium (oxycephaly or brachycephaly). This condition is associated with Apert syndrome a genetic defect in fibroblast growth factor receptor 2 FGFR2 that effects ossification of the sutures). If the coronal or lambdoid suture closes prematurely on one side, the cranium becomes twisted and asymmetric (plagiocephaly). If the frontal (metopic) suture closes prematurely this leads to a sharp keel shaped deformity of the frontal bone (trigonocephaly). Depending on the severity, these conditions may be treated by surgery or by the use of specially fitted, corrective headgear, worn by infants to reshape the head.
What is Cleidocranial dysostosis?
An autosomal dominant mutation of a transcription factor encoded by the CBFA1 gene affects intermembranous ossification and development of the teeth (e.g., abnormal development and late eruption of the teeth, and the formation of supernumerary adult teeth). The clavicles may be partial or absent giving the patient increased mobility of the shoulders. The bones of the calvaria may be poorly mineralized, and the fontanelles may never fully close or be delayed in closing. There may be bossing (bulging) of the frontal, parietal and occipital bones.
What is Arnold-Chiari syndrome?
Arnold-Chiari syndrome results in displacement of the medulla and part of the cerebellum, through the foramen magnum, into the spinal canal. This may block the flow of cerebral spinal fluid, and lead to a form of hydrocephalus. This defect is not fully understood but may arise from abnormal development of the posterior fossa of the skull, which normally contains the cerebellum and medulla, or it may be related to hypertrophic growth of the cerebellum. The condition may be asymptomatic or may lead to a range of problems (e.g., lack of motor control, headaches, etc.). More severe forms of this malformation are often accompanied by spina bifida and menengomyelocele or myeloschisis, due to abnormal localized accumulation of CSF within the brain or spinal cord. Treatment involves surgical decompression (e.g, surgery of the skull).
What 2 parts does the forebrain consist of?
the more anterior, telencephalon and the posterior diencephalon
What does the telencephalon give rise to?

What does the diencephalon give rise to?

What is the lamina terminalis?
paired cerebral vesicles or hemispheres, which initially form as bilateral out pockets.

epithalamus (dorsally), the thalamus and the hypothalamus (ventrally)

The lamina terminalis represents the anterior, midline tissue that lies between the cerebral vesicles (hemispheres).
How is the forebrain organized? How is it evident?
the forebrain is also organized in a segmental fashion, as six prosomeres. This segmental organization is not overtly obvious at the morphological level, but is revealed by the segmental expression of specific genes, including homeobox containing genes (e.g., Hox genes). The pattern of expression is further elaborated with increasing developmental time. These homeobox genes encode transcription factors that regulate downstream gene expression. Such genes are expresses in a collinear fashion in transverse overlapping bands and longitudinal stripes that serve to control development, and regional (axial) differences within the entire CNS, as well as in other tissues.
What gives rise to epithalamus, thalamus and hypothalamus?
Which of the 3 remains small/
alar plates thicken in three regions in the diencephalon

epithalamus
What forms the pineal body or epiphysis? What is its function?
The most caudal part of the roof plate in the diencephalon

the epiphysis plays an important endocrine role in the regulation of circadian rhythms via production of melatonin, and in sexual development, etc.
What is the posterior lobe or neurohypophysis derived from? What is that derived from?
posterior lobe or neurohypophysis of the pituitary gland is derived from the infundibulum, which develops from the ventral surface of the diencephalons (hypothalamus), as previously described.
Where is the thalamus?
The thalamus lies at the dorsoventral level appropriate for receiving somatic afferents.
Where is the hypothalamus?
The hypothalamus lies at the level to receive visceral afferents.
What gives rise to the cerebral hemispheres?
cerebral vesicles
What stimulates the growth of the cerebral hemispheres?

What is the cerebral hemispheres like early during development?
Pressure from the CSF

Early during development the cerebral hemispheres possess a kidney bean shape and a smooth surface.
What do the hemispheres cover?

What forms between the hemispheres?
These hemispheres eventually meet at the midline to cover the lamina terminalis, the diencephalon, and the midbrain.

falx cerebri-
fold of the dura mater called the
What is the interventricular foramen of Monro?
What narrows the interventricular foramen of Monro?
The junction between the lateral ventricles, and the third ventricle

growth of the lateral hemispheres
What and where is the choroid plexus?
At the junction between the roof of each hemisphere and the thin roof of the third ventricle is a choroid fissure. The choroid plexus develops along each of these fissures that protrudes into the lateral ventricles. These plexi extend into the interventricular foramen (of Monro) and meet the choroid plexus that forms in the roof of the third ventricle.
What is the pallium?
The pallium (cloak) represents primarily the mantle layer (gray mater) and marginal zone (white mater) of the telencephalon that forms the cerebral cortex and envelopes the brain stem.
Where is the hippocampus?
Adjacent to each fissure, each hemisphere forms the hippocampus.
Where is the paleopallium?
Where is the Neopallium?
Where does the corpus striatum form?
Laterally and dorsally lies the paleopallium.

Between the hippocampus and paleopallium lies the greatly expanded Neopallium.

The floor of each hemisphere thickens and forms the corpus striatum.
Why does the cerebral cortex grow in a C-shape?
Adjacent to the lamina terminalis the corpus striatum does not expand as rapidly as the other tissues in the cerebral hemisphere. The cerebral cortex of the cerebeller hemispheres therefore grow and curve into a folded, C-shape, with one end terminating in the frontal lobe and the other in the temporal lobe.
What creates the lateral fissure? What is the lateral fissure associated with?

What folds form on the surface of the brain?
The central cleft creates the lateral fissure, which is associated with the insula (cortex lying adjacent to the corpus striatum) and the corpus striatum.

the various ridges (gyri) separated by grooves (sulci).
Besides the cerebral cortex, what other structure become C-shape?
The limbic cortex, lateral ventricles of the cerebral cortex and corpus callosum also become C-shaped.
Where is the subventricular layer? When does it produce cells and what kind of cells does it produce?
At the cellular level, the subventricular zone is established as a second germinative layer between the apical, ventricular zone and the mantle layer. The subventricular zone remains mitotically active after much of this activity ceases in the ventricular zone and continues to generate glial cells and neurons.
What forms the cortical plate? What does the cortical plate form?
Cells from the mantle zone

cerebral cortex
What cells arrive first to the cortical plate?
How do the rest of the cells form?
principle neurons or pyramidal cells
Newer cells push past the old cells, forming the plate inside out
What becomes the white matter of the cerebrum?
The zone between the ependyma and the cortical plate, the intermediate zone, becomes the white mater of the cerebrum.
What properties of neurons are determined before and after neurogenesis?
Experimental studies reveal that cell fates are determined before the cells begin to migrate to their final positions. These studies also reveal that neurons and glia arise from separate progenitor cells. Thus, the lineage of pyramidal and non-pyramidal cells has diverged by the onset of neurogenesis, and the laminar position to which a neuron will migrate is determined while it is in the ventricular zone. Some properties of a neuron may be influenced by environmental cues during or after migration (e.g., neurotransmitter synthesis). Likewise, environmental factors, such as positive and negative guidance cues, help direct the routes of migration of specific cells.
What are the refractory elements, the lens and the cornea, derived from?
Refractory components, that include the lens and cornea, are derived from the head ectoderm that lies adjacent to the developing forebrain (the so-called “placodal ectoderm”)
What do the neuronal, sensory components of the eyes form as bilateral outgrowths of?
The neuronal, sensory components of the eyes form as bilateral outgrowths of the central nervous system (i.e., optic vesicles of the diencephalon).
What are the three tissues the eyes are derived from?
neurectoderm of the CNS, anterior (head) ectoderm, and the neural crest.
What signals control growth of the eye?
The development of these tissues is controlled by mutual cell-cell inductive interactions (so-called secondary inductive interactions) involving the developing retinal and lens tissues, as well as other tissues, such as the mesoderm that underlies the lens placode early during development.
What is Coloboma iridis?
An inferior (ventral gap will appear in the iris that may be of little consequence. The cleft may also extend into the ciliary body, the retina, the choroid ,or even the optic nerve. Other problems may occur related to the persistence of the distal part of the hyaloid artery within the vitreous chamber, which normally degenerates.
Why does congenital cataracts form?
Congenital cataracts may form as a result of defects in the development of the lens. These may arise due to various genetic conditions (e.g., aniridia, Down syndrome, galactosemia or the failure to metabolize galactose) or may form as a result of certain congenital infections, such as rubella virus, toxoplasmosis or congenital syphilis.
Why do micropthalmia and anopthalmia form?
Micropthalmia (a small eye) or anopthlamia (no eye) are conditions related to specific genetic defects (e.g., , trisomy 13, or aniridia) and may also be caused by fetal infection (intrauterine infections of the TORCH group, e.g., , toxoplasmosis, rubella virus, cytomegalovirus and herpes simplex virus that cross the placental barrier during the late embryonic or early fetal period). Eyelids do form in cases of anopthalmia, but other eye tissues are absent, due to failure of development of the optic vesicles (primary) or the forebrain (secondary).
Why does aniridia form? What happens?
The Pax6 gene encodes a transcription factor required for normal eye development.
Aniridia (e.g., in heterozygous pax6 mutant individuals) is a rare condition in which the iris fails to form and there are lens cataracts and other eye problems, such as micropthalmia.
What is Retinoblastoma?
Retinoblastoma (RB) is a retinal tumor of childhood that is derived from persistent pluripotent stem cells of the immature retina. The condition is initially apparent with a white pupil (“cat’s eye reflex,” ) called “leukocoria.” The RB gene, located on chromosome 13, is a tumor suppressor gene, encoding a regulatory factor that normally suppresses progression of the cell cycle. Hereditary RB causes multiple tumor formation in both eyes. Non-hereditary RB leads to the formation of a tumor in only one eye.
What causes Cyclopia?
Various signaling factors are responsible for the bilateral division of the CNS (e.g., Sonic Hedgehog and BMPs). If the forebrain fails to be properly patterned, a single eye or two close-set eyes will form at the midline of the presumptive forebrain. This is associated with other severe brain defects and is not a viable condition.
What causes Retrolental fibroplasia ?
Retrolental fibroplasia (retinopathy of prematurity) represents an oxygen-induced condition of retinopathy seen in premature infants thought to follow excessive oxygen therapy for respiratory distress. This leads to abnormal growth and proliferation of retinal blood vessels and subsequent problems involving retinal detachment may occur.
What causes Persistent iridopupilary membrane?
Normally a thin layer of connective tissue covers the developing lens, which is derived from surrounding mesenchyme located in the eyecup. This tissue subsequently degenerates. Small strands may persist from this iridoupilary membrane that cross the visual path. Generally these are of little consequence.
What causes congenital deafness?
Conduction deafness results when there is an interruption in the passage of sound waves through the ear. Structures of the inner ear may be otherwise fairly normal. This may result from a wide variety of conditions, such as those related to auricular atresia or absence of the external acoustic meatus (see below) or to defects in the development of the bones of the middle ear which can accompany first arch syndrome. These issues may be corrected surgically or with a cochlear implant.

Other types of congenital deafness (and nerve deafness ) may be related to a variety of genetic factors or due to abnormal development of the spiral organ of corti, which results from exposure to rubella virus, (particularly during weeks 7-8 of development) a critical period for the development of this structure.
What causes atresia of the xternal auditory meatus?
Partial or complete atresia results from failure of canalization of the meatal plug. Partial atresia results in the presence of a soft-tissue plug in the location of the tympanic membrane. Total atresia results in the presence of a boney plate in this location. These defects are often associated with first arch syndromes or defects of the second arch.
What is associated with aurical malformations?
Minor auricular malformations accompany several genetic conditions, including Down syndrome (trisomy 21) Patau syndrome (trisomy 13) and Edwards syndrome (trisomy 18), as well as first arch syndrome.
What is and what causes Microtia?
Microtia refers to a condition in which there is a very small, disorganized auricle and is generally associated with atresia of the external acoustic meatus (see below) and other middle ear malformations resulting in deafness. The condition is related to inadequate development and fusion of the auricular hillocks.

Such auricular defects have other consequences such as affecting the patient’s ability to wear glasses or headphones. Reconstructive surgery can restore the auricle and correct these issues.
What are auricular appendages?
Auricular appendages (more typically unilateral and located anterior to the auricle, in the “pretragal area”) are external skin tags that result from abnormal development of the auricular hillocks or to the formation of accessory auricular hillocks. These structures are generally more of a cosmetic issue and can be easily removed.