Structure And Function - Embrology

Front 1

Describe phases of spermatogenesis

Back 1

Phase 1: Spermatogonia ---meiosis I and II---> Spermatids

Phase 2: Spermatids---spermiogenesis--->spermatozoa

Front 2

Describe morphology of spermatozoa

Back 2

Front 3

What glands contributes to the seminal fluid?

Back 3

25. Seminal vesicle - 60%

14. Prostate gland - 30%

26. Bulbourethral Gland - 10%

Front 4

Lack of sperm in semen is called?

Deficiency in sperm is called?

The seminal fluid functions to?

Back 4

Azoospermia (zero), oligospermia (some)

1. provide a nutrient source for the spermatozoa

2. to neutralize vaginal acidity

3. promote sperm motility

Front 5

1. What is the normal site of fertilization?

2. The spermatozoa that do not get pumped up the fertilization site colonize what part of the uterus?

Back 5

1. Ampulla of the uterine tube

2. The cervical crypts

Front 6

Describe the two non disjunction events that could lead to aneuploidy

Back 6

non disjunction in meiosis I

- Gametes are N = 24, 24, 22, 22.

- Fertilization = 24 or 22 + normal 23 = 47 (trisomy) or 45 (monosomy). No gametes are normal.

non disjunction in meiosis II

- Gametes are N = 24, 22, 23, 23.

- So one 1/4 will have 24 (will make trisomy) and 1/4 will have 22 (monosomy). 1/2 of gametes are normal.

Front 7

What can Aneuploidy arise from?

Back 7

Aneuploidy (abnormal chromosome numbers) can come from non disjunction - the failure of chromosomes to separate during meiosis I or II.

Front 8

What is capacitation?

Back 8

• A process that creates fully functional spermatozoa

• After 4 – 6 hours in the female reproductivetract

• Increased motility and metabolism

• Necessary for:

1. Sperm – egg attachment

2. Acrosome reaction

Front 9

Follicles

Back 9

The cellular units that contain the developing egg (oocyte)

Front 10

Blastomeres

Back 10

- totipotential cells produced from mitotic divisions (cleavage)

Front 11

What is a Morula?

What happens at this stage?

Back 11

8 cell (8 blastomeres) stage.

Compaction:

- increase contact of cells to make a circle.

- Differentation starts - formation of trophoblast (implantation + placenta) and inner cell mass (embryo, amniotic mem. and yolk sac)

- between 3rd and 4th cleavage

Front 12

# of chromosomes in somatic cell?

# of chromosomes in gamete cell?

Back 12

46, 23

Front 13

Trace the passage of sperm out of the penis

Back 13

Testis - rete testis- efferent tubules - epididymis - vas deferens - urethra

Front 14

Describe the phases of oogenesis

Back 14

P. Oocyte -> S. Oocyte

- Meiosis I in fetal ovary

- Meisis I stops until just before ovulation

S. Oocyte -> Ovum

- Meiosis II just before ovulation

- Meiosis II stops until fertilization

Front 15

1. graafian follicle

2. Stigma

Back 15

1. Large 2° follicles

- It will go through Meiosis I before ovulation

2. ovarian surface from which graafian follicle will burst out of.

Front 16

Describe the Primordial follicle

Back 16

- 1° oocyte
- single layer of follicular cells (AKA granulosa cells)
- arrested in prophase of Meiosis I

Front 17

Describe the primary follicle

Back 17

- contains 1° oocyte

- Zona Pellucida

- multiple layers of follicular cells

- outer layer: theca (make androgens, which is made into estrogen by follicular cells)

Front 18

Describe the secondary follicle

Back 18

- like 1° follicle but has fluid filled space (antrum)

- contains 1° oocyte

- cumulus oophorus (The oocyte and the follicular cells immediately surrounding)

Front 19

What do the granulosa cells secrete to the inside of the oocyte over the ZP?

What structures allow for secreted proteins and metabolic support to transfer over the ZP?

Back 19

OMI: Oocyte Maturation Inhibitor

- keep the 1° oocyte suspended in the meiosis I

Gap junctions between the granulosa cells and occyte allow for this transfer

Front 20

1. mural follicular cells

2. cumulus oophorus

Back 20

1. follicular cells forming the wall of the antrum in a 2° follicle.

- remain behind in ovary after ovulation

- form granulosa lutein cells of corpus luteum

2. complex made of the occyte and follicular cells immediatly surrounding it.

- project into antrum

Front 21

What is the Corpus Luteum and what is it a remnant of?

Back 21

- Remnant of mural follicular cells left behind after ovulation and theca cells

- will become corpus albicans after 2 weeks (if no fertilization, no hCG)

- if they are maintained then the ovary will stay in a reproductive state

Front 22

Name of follicular cell layer surrounding ZP after ovulation?

Back 22

Corona Radiata

- will fall away after a few days

Front 23

Describe the morphology of the egg as it leaves the ovary

Back 23

- 2° oocyte

- Z.P.

- Corona Radiata

- 1st polar body (from Meiosis I)

Front 24

What will the binding of the sperm to the egg induce?

Back 24

- 2° oocyte start meiosis II

- cortical granules exocytose and change the ZP3 protein so other sperm cannot bind to egg (zona reaction)

Front 25

acrosome reaction

Back 25

- acrosomal enzymes (hyaluronidase and acrosin) released from acrosome to get through ZP3 in the Z.P.

- species specific

Front 26

male and female pronuclei

Back 26

- female pronucleus formed after meiosis II (discard the second polar body)

- sperm will break down to the male pronucleus within 12 hours of entering the 2° oocyte.

- the two nuclei join to restore diploid number of 46

Front 27

Day 4 after fertilization?

Back 27

Blastocyst stage:

~ 32 cell stage

- fluid enters morula making balstula

- blastocyst cavity

- still surrounded by ZP

Front 28

Cleavage

Back 28

A series of comparatively rapid mitotic divisions resulting in progressively larger numbers of progressively smaller cells.

- 1st cleavage is 24 hours after meiosis II (production of 2nd polar body)

- subsequent divisions are 12h-24h after

- between 3rd and 4th cleavage division: compaction

Front 29

What happens at day 5 and 6 after fertilization?

Back 29

- Hatching (5 days)

- trophoblasts make enzymes

- The embryo breaks out of the zona pellucida

- epithelial cells (of the endometrium) and trophoblast can now contact each other

-Implantation (6 days) Contact occurs between the epithelial cells and the trophoblast.

Front 30

1. Syncytiotrophoblast

2. Cytotrophoblast

Back 30

1. made by fusion of trophoblast cells, invades endometrium

- multinucleated

- source of human chorionic gonadotropin (hCG).

2. after syncytiotrophoblast formed, the trophoblast still on the embryo are called cytotrophoblast

Front 31

What consequences can a previous tubal inflammation (salpingitis) or scarring have for pregnant woman?

Back 31

- delayed passage of embryo through the fallopian tube

- ectopic pregnancy (1:100) after ZP sheds off

Front 32

What happens to the inner cell mass as the embryo implants?

Back 32

- the inner cell mass is converted into a two layered structure called the bilaminar embryonic disc: epiblast + hypoblast

- the inner cell mass also create amniotic membrane surrounding the amniotic cavity

Front 33

Gestational age vs fertilization age

Back 33

Fertilization age: From point of fertilization

Gestational age: From first day of menstrual cycle.

- 2 weeks older than fertilization age.

Front 34

Describe gastrulation.

Back 34

Bilaminar embryo becomes a trilaminar one.

- epiblast cells migrate to one end to make the primitive streak (at the caudal midline i.e. in the middle of the caudal end)

- The cranial end of the primitive streak is called the primitive knot (AKA primitive pit or Hensen's node).

- The epiblast cells ingress at the primitive pit and along the primitive streak (primitive groove) and then begin to migrate laterally and rostrally to caudal end.

Front 35

Describe the three layers formed from gastrulation.

Back 35

- 3 layers, all coming from epiblast cells

- endoderm (replace hypoblast)

- mesoderm

- ectoderm (amniotic cavity facing epiblast cells).

Front 36

Why is there a rostro - caudal gradient in developmental activity?

Back 36

- first cells to migrate rostrally and make rostral structures. They are more advanced than the caudal end.

- primitive streak is still developing the 3 layers in the cuadal end while the rostral tissues proceed with growth, differentiation and organ formation.

- primitive streak gets smaller and smaller (finally dissapears at sacrococcygeal part)

Front 37

Where does the notochord come from?

Back 37

- mesoderm: Epiblast cells which ingress through rostral end of the primitive streak AKA Hensen's node, primitive knot, primitive pit.

Front 38

What does the ectoderm contribute to the formation of?

Back 38

- Nervous system

- Tissues that cover the body surface (epidermis, hair, nails)

- Body surface glands

Front 39

Describe Neurulation.

Back 39

- Notochord + paraxial mesoderm sends signals to part of ectoderm -> differentiate to Neuroectoderm

- Neural folds and Neural groove

- Folds fuse to make the neural tube

- surface ectoderm covers the tube

- Mesoderm cells move up between tube and
and surface ectoderm

Front 40

rostral neuropore and the caudal neuropore

Back 40

Last parts to close in the neurulation process.

Front 41

What does the Neural tube develop into?

What about the surface ectoderm flanking the neural plate?

What about the mesoderm that migrated up between the ectoderm and neural tube?

Back 41

The neural tube develops into the brain and the spinal cord.

The non-neural ectoderm will contribute to the skin covering the brain and spinal cord.

The mesoderm will form the bones of the calvarium, covering the brain and the vertebrae covering the spinal cord.

Front 42

Describe what has happened with Anencephaly or myeloschisis

Back 42

Failure to close the neuropores.

Rostral (anencephaly) and caudal (myeloschisis) neuropores

'Schisis' = breaking up of attachments or adhesions

Front 43

1. As the neural crest cells migrate out of the neural fold and into the body, what do they form?

2. What do the neural crest cells that migrate out from the cranial end of the neural tube also able to form?

Back 43

1.

- DRG sensory neurons

- Postganglionic sympathetic chain

- Postganglionic in prevertebral ganglia

- postganglionic in walls of viscera

2. cranial connective and skeletal tissues

Front 44

What does the endoderm develop into?

Back 44

- lining tissue (epithelium) of gastrointestinal tract

- secretory cells of Liver, G.B. and Pancreas

- lining of the ducts of the organs

- lining of respiratory system

Front 45

Vitelline duct

Back 45

- connects the primitive gut to yolk sac

- formed by the folding of the lateral plate endoderm into the primitive gut

- this is due to somites enlargement

Front 46

What does the mesoderm divide into?

Back 46

- paraxial mesoderm

- lateral plate mesoderm

- intermediate mesoderm

Front 47

What are the somites?

Where are they derived from?

What will they develop?

Back 47

- derived from paraxial mesoderm

- form blocks of cells in craniocaudal sequence

- will develop vertebrae, intervetebral discs, ribs, skeletal muscles of body wall and limbs, connective tissue of the body wall

Front 48

What does the intermediate mesoderm form?

Back 48

Kidneys, ureter and gonads

Front 49

What is the intraembryonic coelom?

What is it surrounded by?

What does it form into?

Back 49

Cavity formed from the Lateral plate mesoderm.

- somatic mesoderm (supports ectoderm)

- splanchnic mesoderm (supports endoderm)

- forms into the main body cavities: e.g the pleural, pericardial and peritoneal cavities.

Front 50

What does the intraembryonic (parietal) somatic mesoderm form into?

What about the intraembryonic (visceral) splanchnic mesoderm?

Back 50

The somatic mesoderm contributes to the connective tissues, blood vessels and smooth muscle of the body wall and limbs.

The splanchnic mesoderm contributes to the smooth muscle, blood vessels and connective tissue of the gastrointestinal tract and associated organs.

Front 51

What is the embryonic period?

What is the fetal period?

Back 51

• Embryonic period… 0 to 8 weeks
- First two weeks … transport and implantation
- 3 to 8 weeks … morphogenesis/organogenesis
• Fetal period … 9 weeks to term

Front 52

Organogenesis

Back 52

- ectoderm, endoderm, and mesoderm develop into the internal organs of the organism.

- Starts with the formation of the neural tube and primitive gut

Front 53

Placenta Accreta

Back 53

The placenta forms too deeply into the uterus wall

Front 54

Placenta Praevia

Back 54

Placenta forms on the lower uterine segment

Front 55

What are the lacunae?

Back 55

Spaces developed within the syncytiotrophoblast which are filled with mothers blood and secretions to provide nutrients for embryo (as the syncytiotrophoblast erodes)

Front 56

1. What is the Extra-embryonic mesoderm?

2. What can it be divided into?

Back 56

1. separates the embryo from the cytotrophoblast --> coelom formed within it

2. extraembryonic mesoderm lining the cytotrophoblast and covering the amniotic membrane is called the extraembyonic somatic mesoderm, and that covering the yolk sac is the extraembryonic splanchnic mesoderm.

Front 57

How is the extaembryonic coelom (AKA Chorionic cavity) formed?

Back 57

start off as small coelom in the extraembryonic mesoderm and group together

- by the end the coelom has separated the embryo from the cytotrophoblast except from at the connecting stalk

Front 58

What is the Chorion?

Back 58

1. layer of extraembryonic somatic mesoderm

2. cytotrophoblast

3. syncytiotrophoblast

Front 59

Describe the development of the villi:

Primary--> Secondary--> Tertiary Villi

Back 59

Primary Villi = finger like projections of cytotrophoblasts into syncytiotrophoblast into the decidua.

Secondary Villi = Extraembryonic somatic mesoderm invades the cores of the primary villi

Tertiary Villi = blood vessels develop from the mesoderm in the 2° villi. Spaces without cytotrophoblasts, mesoderm directly in contact with syncitiotrophoblast. Nutrients/waste only needs to cross 2 layers.

Front 60

Describe the 3 regions of the decidua.

Back 60

Inner endometrium of uterus = decidua

Decidua basalis - under location of birth

Decidua capsularis - capsulates embryo

Decidua parietalis - everything else

Front 61

Cytotrophoblastic shell

Back 61

- cytotrophoblasts at the tip of 1° villi will push through syncitiotrophoblast to create shell to anchor chorion to decidua

- these villi = anchoring villi

Front 62

Where are the umbilical arteries and veins derived from?

Back 62

Extraembryonic somatic mesoderm that create vessels which form in the connecting stalk

Front 63

Intervillious spaces

Back 63

Lacunae develop into intervilious spaces

Blood enters from spiral artery

Leave from endometrial veins

Front 64

Smooth Chorion?

Back 64

Villi recede in the decidua capularis, forming the smooth chorion and branch out in the decidua basalis, forming the villous chorion

Front 65

What is the fate of the chorionic cavity?

Back 65

- The amniotic cavity expands, surrounding the embryo. The amniotic membrane envelops the connecting stalk --> outer membrane of the umbilical cord.

- The amniotic membrane becomes applied to the chorion (amniochorionic membrane).

Front 66

What is the fate of the uterine cavity?

Back 66

- implantation site expands into the uterine cavity until the decidua capsularis comes into contact with and fuses with the decidua parietalis.

Front 67

What are the features of a full term placenta?

Back 67

- placental septae (decidua basalis tissue between enlarged intervillous spaces)

- cotyledons - collections of villous trees (cobble stones on outer placenta covering)

Front 68

What is inside the umbilical cord?

Back 68

- 2 umbilical arteries delivering oxygen depleted blood from the fetus to the placenta (becomes superior vesical arteries and the medial umbilical ligaments).

- 1 umbilical vein delivering oxygen rich blood to the fetus (becomes ligamentum teres)

- The vitelline duct (yolk stalk) and the allantois in the proximal portion.

- Wharton's jelly; a gelatinous connective tissue that supports the vessels.

Front 69

monozygotic vs dizygotic twins?

Back 69

- anastamoses may occur in monochorionic, monozygotic twins causing twin-twin transfussion syndrome

Front 70

Name 3 placental pathologies

Back 70

- Placenta accreta = Abnormally deep attachment of the placenta – ie to the myometrium or deeper.

- Placenta praevia= Placenta is abnormally placed, very close to partially or fully covering the internal os.

- Placenta abruption = Partial or complete separation of the placenta from the uterus before labour.

Front 71

What does the splanchnic mesoderm form?

What does the endoderm form in the gut?

Back 71

Mesoderm:

- smooth muscle, connective tissues and blood vessels that are associated with the derivatives of the primitive gut.

Endoderm:

- forms the tissue lining the digestive tract and lining its outgrowths

- secretory cells (parenchyma)

- lining of the ducts

Front 72

Meckel's diverticulum

Where else can there be Diverticulae?

Back 72

- vitelline duct connects antemesenterically at the primitive midgut at the distal ileum. If it persists then it will form a diverticulum.

- Diverticulae and cysts can also occur if the notochord and the endoderm fail to separate

Front 73

When week of development does the embryo start to fold?

What is the cloacal membrane?

Back 73

4th week: longitudinal and transverse folding

Membrane separates the cloaca from the proctodeum, a pit-like depression on the external surface of the embryo.

Front 74

What does the foregut give rise to?

Back 74

- respiratory tree from the larynx to the alveoli. -esophagus

- stomach

- duodenum as far as the entrance of the common bile duct

- liver, gall bladder, and pancreas

Front 75

What reverses the process of occlusion in the foregut after gastric dilatation?

Back 75

- recanalization by cavitation

- failure to do so will give rise to stenosis or atresia

Front 76

What are the 8 steps of the foregut formation?

Back 76

1. formation of the laryngotracheal diverticulum

2. appearance of the gastric dilatation

3. elongation of the esophagus (stomach-->abdomen)

4. occlusion (promixal and distal to gastric dilation)

5. recanalization

6. stomach rotation

7. differential growth

8. outgrowth of the liver, gall bladder and pancreas

Front 77

The midgut develops into?

Back 77

- duodenum distal to the opening of the common bile duct.

- the jejunum and ileum

- the cecum and appendix

- the ascending colon and the proximal part of the transverse colon.

roughly corresponding to the field supplied by the SMA.

Front 78

3 steps of the midgut formation?

Back 78

1. Elongation of the midgut and herniation of the midgut loop in the midline into the umbilical cord

2. Further elongation of the proximal half of the midgut loop creating the coils of the smallintestine. Rotation of the loop 90° counter – clockwise (towards the embryo's right).

3. Return of the midgut loop to the abdominal cavity. 180° further rotation counter-clockwise. Distal part of midgut elongates causing cecum to descend.

Front 79

Omphalocele

Back 79

- intestines lie within the umbilical cord because it failed to return back into the gut. It is covered with the translucent amniotic membrane that covers the cord externally.

Front 80

Gastroschisis

Back 80

- resulting from a rupture in the anterior body wall, usually on the right hand side of the umbilical cord. The intestines are not covered and float freely in the amniotic fluid

'Schisis' = breaking up of attachments or adhesions

Front 81

The hindgut gives rise to?

Back 81

- the distal part of the transverse colon

- the descending colon

- the sigmoid colon

- the rectum

- the upper part of the anal canal

Front 82

Hindgut development:

The urorectal septum partitions the cloaca into?

Back 82

- urogenital sinus

- rectoanal canal

Front 83

Imperforate Anus

Back 83

results from dorsal deviation in the path of the growth of the urorectal septum.

If the urorectal septum fuses with the posterior wall of the cloaca, rather than the cloacal membrane, it will result in complete atresia.

Front 84

Fistulae during urogenital development

Back 84

Incomplete fusion near the leading edge of the urorectal septum (bifid).

Can cause the urogenital and rectoanal canals to maintain a connection.

Front 85

Meconium

Back 85

- made up of secretions, cells sloughed from the gut walls and cells and lanugo hairs that have been swallowed with the amniotic fluid.

- makes up the contents of the fetal intestine

Front 86

What portion of the pancreas is from the dorsal pancreatic duct?

Back 86

dorsal pancreatic bud = head, body, tail of pancreas, main + accessory pancreatic duct

ventral pancreatic bud = Uncinate process, hepatopancreatic ampulla

Front 87

Causes of obstruction

Back 87

- Failure to recanalize (stenosis or atresia)

- Fetal vascular accident (blood supply compromised to section of bowl)

- Congenital hypertrophic pyloric stenosis

- Annular pancreas

- Congenital volvulus (twist of intestines)

- Intussuception (small intestine go into large intestine)

- Imperforate anus

- Congenital membranous atresia (anal membrane fails to break down)

- Meconium ileus

Front 88

Polyhydramnios

Back 88

- an excess of amniotic fluid in the amniotic sac due to obstruction of gut

Front 89

Meconium ileus

Back 89

If the meconium is too viscous, the newborn may not be able to pass it and so it becomes a source of obstruction.

Front 90

When does the laryngotracheal diverticulum start to form and what does it form from?

Back 90

- 4th week

- endoderm lining of foregut (ventral wall on rostral end)

Front 91

What does the endoderm of the laryngotracheal diverticulum develop into?

What about the surrounding splanchnic mesoderm?

Back 91

Endoderm --> epithelium lining airways and pneumocytes lining the alveoli

Splanchinc mesoderm --> pleura, connective tissue, muscles and vessels of the lungs

- controls the branching of bronchi on the larygotracheal tube

Front 92

Tracheo-esophageal Fistula

Back 92

1:3000

Front 93

What lines the primitive pleural cavities?

The parietal pleura can be subdivided into?

Back 93

- The primitive pleural cavities are lined with a pleural membrane derived fromsplanchnic mesoderm.

- The costal pleura

- The diaphragmatic pleura

- The mediastinal pleura: middle area

- The cervical pleura: AKA cupola.

Front 94

What do Type II pneumocytes secrete?

Back 94

Surfactants, to reduce the surface tension in the alveoli making lungs easy to inflate.

Front 95

What happens to a baby's breathing if there is not enough surfactant produced or if surfactants are over consumed?

Back 95

- increased work for respiration

- hyaline membrane disease

- respiratory distress

- Infant respiratory distress syndrome

Front 96

What are 4 strategies to prevent respiratory distress?

Back 96

- baby stays in uterus longer

- speed maturation by giving hormones to mother

- predict those with pulmonary immaturity

- administer surfactants to baby

Front 97

What are 4 things the growth of the lungs in utero depends on?

Back 97

- physical space in the thorax

- fetal lung fluid (lung needs to produce its secretions)

- amniotic fluid access (growth factors inside)

- practice breathing (with amniotic fluid)

Front 98

What forms the diaphragm in the fetus?

Back 98

- cranial part of the septum transversum (ventral mesentery)

- dorsal mesentery of foregut (abdominal esophageal portion)

- pleuroperitoneal folds

Front 99

What seals the pleuroperitoneal canals in the 9th week of development?

Back 99

The pleuroperitoneal folds. The left fold is slower in growing over the canal.

Front 100

Congenital Diaphragmatic Hernia

Back 100

Left pleuroperitoneal fold doesn't close in time. In the 10th week, the abdominal organs move up into the thorax.

Fetoscopic Tracheal Occlusion (FETO) can be used to counter this by plugging the trachea, lungs will grow and push viscera down.

Front 101

Describe the hierarchy of pleural branching starting with the trachea.

Back 101

- trachea
- 1° / principle bronchi (to each lung).
- 2° / lobar bronchi (to each lobe)
- 3° / segmental bronchi
- terminal bronchiole
- respiratory bronchiole
- alveolus

Front 102

1. What does repeated branching of the larygotracheal tube form?

2. What controls this branching?

Back 102

1. Forms the bronchi

2. Mesoderm controls the branching and determines the identity of the airway

Front 103

What embryonic structure forms the bladder and urethra?

What forms the kidneys and ureters?

Back 103

Cloeca ---> urogential sinus ---> bladder and urethra

The intermediate mesoderm ---> nephrogenic cords ---> metanephric mass and ureteric bud ---> kidneys and the ureters.

Front 104

1. What cord does the intermediate mesoderm condensate to become?

Back 104

nephrogenic cords

Front 105

In the pronephric phase, the pronephric duct grows towards the sacral end of the embryo to open up to?

Back 105

The cloaca

Front 106

During the fourth week, the ________ part of the nephrogenic cord and the associated (cervical) part of the __________ duct degenerate and forms _________. The remainder of the duct persists and referred to as ____________ duct.

Back 106

Pronephric, Pronephric, Vesicles, Mesonephric

Front 107

What does the metanephric mass signal (with GDNF) to mesonephric duct to do?

Back 107

Make an outgrowth: The Ureteric Bud, which sends signals out to to the mass to make it survive.

Front 108

1. What are the derivatives of the ureteric bud?

2. What are the derivatives of the metanephric mass?

Back 108

1. The urine collecting system - i.e. Calyces, Renal pelvis, Ureter, collecting tubules, collecting ducts, etc.

2. The urine producing system - i.e. the nephrons of the kidney (renal corpuscles, proximal and distal convoluted tubules and the loops of Henle).

Front 109

The ends of the ureteric bud branches induce the metanephric mesoderm to organize into?

Back 109

Metanephric vesicles, which end up attaching to the ducts.

(bud = dark grey, mass = light grey)

Front 110

As the kidneys ascend and rotate medially, what happens to the renal arteries?

Back 110

The renal arteries also ascend up the aorta.

Front 111

What is happening to the development of the kidney in Multicystic Kidney, Recessive Polycystic Kidney Disease, and RPKD?

Back 111

The nephric vesicles are not properly developing to the tubules.

Front 112

After the ureteric bud signals the metanephric mass to survive, what does the metanephric mass signal to the ureteric bud?

Back 112

To start branching

Front 113

After the ureteric bud starts branching, what does the ureteric bud signal to the metanephric mass?

Back 113

To start Tubulogenesis/condensation: start creating tubles

Front 114

What are some Abnormalities of the kidney ascent?

Back 114

- accessory renal arteries

- ectopic kidneys (if it doesn't asend, it will not rotate medially)

- Fused kidneys (can't ascend past the SMA, therefore also ectopic)

Front 115

What are some abnormalities between the interaction of the metanephric mass and ureteric bud?

Back 115

- bifid ureter (bud splits before entering mass)

- supernumerary kidney (bud splits before entering mass with large distance in between buds or two buds develop from the mesonephric duct)

- crossed ectopian

- Renal Agenesis (failure of the bud and mass to interact)

Front 116

What are the two types of renal agenesis?

Back 116

Unilateral: failure of one kidney to form.

Bilateral: leads to the oligohydramnios syndrome: Potter's facies, flexion contractions, pulmonary hypoplasia

Front 117

Pulmonary Hypoplasia

Back 117

Lungs do not fully develop. Can be caused by a deficiency of amniotic fluid.

Front 118

Oligohydraminos

Back 118

Deficiency of amniotic fluid, which is needed for fetus to move limbs, practice breathing and get growth factors going into lungs and intestines.

Front 119

The fetus regulates the volume of amniotic fluid.

1. How does it increase the amniotic fluid volume?

2. How does it decrease the amniotic fluid volume?

Back 119

1. urinating

2. swallowing

Front 120

When the fetus swallows the extra amniotic fluid where does it go?

Back 120

It is absorbed through the fetal intestine into the fetal circulation. The volume is then passed across the placenta into the maternal circulation. Excess volume can then be cleared through the maternal kidneys.

Front 121

What could be some causes of oligohydramnios?

Back 121

Inability to urinate into amniotic fluid:

• Bilateral renal agenesis

• Posterior urethral valve (a remnant of the urogenital membrane)

• Bilateral polycystic kidney disease

• Premature rupture of the membranes (mother is leaking corionic fluid)

Front 122

What could be some causes of polyhydramnios?

Back 122

Inability to swallow amniotic fluid:

- foregut obstruction

- Anencephaly (distrupted cranial development, fetus has no reflexes to swallow)

Front 123

Patent Urachus

Back 123

Allantois does not close properly and so there is still a passage from bladder--->umbilicus

Front 124

Bladder Extrophy

Back 124

Urogenital sinus endoderm joins the ectoderm after a wound on ectoderm.

Bladder will be facing the outside of the baby's body.

Front 125

What does the allantois regress to form?

Back 125

The urachus and subsequently the median umbilical ligament.

Front 126

Common excretory duct

Back 126

The segment of the mesonephric duct that lies between the urogenital sinus and the point at which the ureteric bud opens into the duct.

Front 127

What does the urogenital sinus develop into?

Back 127

Bladder and urethra.

Bladder = superior expansion of sinus

Urethra = distal part of sinus remaining narrow

Front 128

Indifferent stage

Back 128

Stage where you cannot tell the difference between M and F embryo.

- first 7 weeks of development

- can only tell M from Y chromosome, HY antigen

Front 129

At 3 weeks, the nephrogenic cord forms pronephric vesicles. What do these vesicles in the pronephros fuse to form?

Back 129

The pronephric duct

Front 130

What does the portion of the cloaca, which the pronephric duct grows into become?

Back 130

Urogenital sinus

Front 131

1. At 4 weeks, what part of the pronephric duct degenerates?

2. What is the name of the duct remaining after this degeneration?

Back 131

1. After the pronephric duct is formed, the pronephros part degenerates.

2. mesonephric duct

Front 132

What does the metanephric mass grow out from?

Back 132

mesonephric duct (AKA Wolffian ducts)

Front 133

The gonadal or genital ridge grows medially to which structure?

Back 133

mesonephros

Front 134

What forms the sex cords in the gential ridge?

Back 134

coelomic epithelium penetrating the intermediate mesoderm

Front 135

If there is no Y chromosome, what do the primodrial germ cells and sex cords develop into?

Back 135

PMG ---> Oogenia (later becomes oocyte)
Sex cords ---fragment into---> Follicular cells

Front 136

If there is a Y chromosome (with SRY gene), what happens to:

1. Sex cords

2. Cells in the mesoderm of the genital ridge

3. PMG

Back 136

1. sex cords ----> seminferous tubules. The cells form the Sertoli Cells capable of secreting Antimuellerian hormone (AMH)

2. Differentiate into Leydig cells (secrete testosterone)

3. Spermatogonia

Front 137

What happens in the trans-abdominal phase of the descend of the testis?

Back 137

- passive process

- gubernaculum (black in picture) pulls testis to mouth deep inguinal ring

Front 138

What happens in the trans-inguinal phase of the descend of the testis?

Back 138

- active process

- vaginal process follows gubernaculum to scrotum and acquires layers of abdominal wall to make the spermatic cord

- testes and vas deferens follow the same path as the vaginal process, pushing it to the side.

- distal end of process becomes the tunica vaginalis

Front 139

Name of condition where the testis do not descend.

Back 139

Cryptorchid Testes

Front 140

What are some abnormalities of the processus vaginalis?

Back 140

Hydrocele or congenital hernia

Front 141

What does the gubernaculum form in the female?

Back 141

The part of the gubernaculum between the ovary and the uterus becomes the ligament of the ovary and the part between the uterus and the labium majus becomes the round ligament of the uterus.

Front 142

True or False: The Vaginal Process is present in both males and females.

Back 142

True.

Front 143

As the paramesonephric ducts enter the pelvis, they cross anterior to the mesonephric ducts and fuse together in the midline to form the?

Back 143

Uterovaginal Primordium.

- lies posterior to the urogential sinus

Front 144

What is created from the endoderm of the urogential sinus when the uterovaginal primodium makes contact with it?

Back 144

The sinovaginal bulb or vaginal plate

Front 145

What does the antimullerian hormone from the Sertoli cells of the seminiferous tubules induce?

Back 145

Cause the paramesonephric ducts and the uterovaginal primordium to degenerate.

- prostatic utricle and appendix of testis are remnants of these

Front 146

The prostatic utricle and the appendix of the testis are thought to be remnants of?

Back 146

Uterovaginal primordium ---> Prostatic utricle

Cranial end of the paramesonephric ducts ---> appendix of testis

Front 147

What do androgens from the Leydig cells of the developing testes induce with the mesonephric tubule and duct?

Back 147

1. the mesonephric excretory tubules to link with the rete testis forming the efferent ductules.

2. the mesonephric duct to develop into the epididymis, vas deferens and ejaculatory duct.

3. the seminal vesicles to develop as outgrowths of the mesonephric ducts.

Front 148

What happens to the paramesonephric ducts and uterovaginal primordium in the absence of antimullerian hormone?

Back 148

Paramesonephric ducts ---> Uterine tubes

Uterovaginal primordium ---fuse---> Uterus

Front 149

In the absence of testosterone, the mesonephric ducts degenerate.

What are some remnants of the duct?

Back 149

Found in the broad ligament:
- epoophoron
- paroophoron

In uterus:
- gartner's cyst

Front 150

What can happen if the paramesonephric tubule does not fully fuse to create the uterovaginal primodium?

Back 150

Divided uterus

Front 151

What does the vagina develop from?

Back 151

- uterovaginal primordium and the endoderm of the urogenital sinus via the vaginal plate.

Front 152

What is the hymen (covering over vagina) developed from?

Back 152

Endoderm of the urogenital sinus via the vaginal plate.

Front 153

What can happen if the hymen does not open at birth?

Back 153

Secretions from vagina and uterus can build up and get large (hydrometrocolpos). Can also lead to bladder being compressed and consequent hydronephrosis/kidney damage.

Front 154

What are the 5 swellings present in the indifferent genitalia (up to 9 weeks of development)?

Back 154

2 x swellings
2 x fold
1 x tubercle

Front 155

What do the 5 swellings of the indifferent genitalia form in the female?

Back 155

- the genital tubercle ---> glans clitoris

- the urogenital folds ---> labia minora

- the labioscrotal swellings ---> labia majora

Front 156

What does the ingrowth of epithelium on the ventral surface of the genital tubercle in males create?

Back 156

Glandular Plate

Front 157

True of False: The mesonephric duct will wait for androgen for an indefinite amount of time.

Back 157

False. The mesonephric duct will wait for chemical signals for a short amount of time. The external genitalia will wait for a longer amount of time.

Front 158

At 10 weeks, what causes the genitals to masculanize?

Back 158

Androgens from Leydig Cells in Testes, which are made into dihydrotestosterone in the target cell.

Key point: reductase is vital for masculinization of the indifferent genitalia but not of the mesonephric duct and tubules.

Front 159

At 8 weeks, what causes the mesonephric duct and tubules to masculanize?

Back 159

Androgens from Leydig Cells in Testes

Front 160

What would happen to a 46XX embryo producing too much testosterone?

Back 160

Gonads = Ovaries (XX genes)

Male Ducts = No (androgen is being overproduced but the span of time the mesonephric ducts (MD) can respond to androgens is short.)

Female Ducts = Yes (no testes, no AMH)

Genitalia = masculanized (androgen is over produced and the ext. genitalia span of time it responds to the androgen is long)

Front 161

What would happen to a 46XY embryo unable to reduce testosterone?

Back 161

Gonads = Testes (listen SRY gene)

Male Ducts = Yes (androgen is being picked up by target cell)

Female Ducts = No (AMH is being produced by sertoli cells in testes)

Genitalia = Feminized (androgen is picked up but not converted to dihydrotestosterone)

Front 162

What would happen to a 46XY embryo where the indifferent genitals do not develop (streak ovary)?

Back 162

Gonads = streak ovary

Male Ducts = No (no testes, no leydig cells, no androgen)

Female Ducts = Yes (AMH is not produced)

Genitalia = Feminized (no testes, no leydig cells, no androgens)

Front 163

1. How long does spermatozoa remain viable for in the female reproductive tract?

2. How long do oocytes live for?

Back 163

1. around 5 days

2. 24 hours

Front 164

What are the species specific and species non-specific phases of fertilization?

Back 164

Species specific = Acrosome reaction (ZP and sperm cell)

Non-species specific = Ligand binding of sperm membrane to 2° oocyte membrane

Front 165

What is shed during parturition and menstruation?

Back 165

The endometrium's layers of epithelium and connective tissue that receive the embryo during implantation.

- form contact with trophoblast in implantation

Front 166

True or False:

While migrating from the ampulla to the uterus (via cilia and smooth muscle), there is no net growth in size of embryo

Back 166

True. The embryo is still retained in ZP until it hatches (day 5) so even though the cell numbers increase, the overall size does not get bigger.

Front 167

True or False:

The hypoblast is responsible for the ectoderm formation.

Back 167

False. The hypoblast is replaced by endoderm in gastrulation. Consequently the hypoblastmakes no direct tissue contribution to the fetus. The epiblast will be responsible for the fetus.

Front 168

What happens to the corpus luteum if the embryo dies or no fertilization of the egg takes place?

Back 168

- if embryo dies, no hCG produced from syncytiotrophoblast.

- If no hCG is present then the corpus luteum will regress, the uterus will slough and the next cycle starts

Front 169

What happens to the corpus luteum if the ovulated egg is fertilized?

Back 169

The syncytiotrophoblast of the embryo will produce hCG, which will block the regression of the corpus luteum

Front 170

What are the 2 layers before gastrulation and what are the 3 layers after gastrulation?

Back 170

Before:

- epiblast (face amniotic sac)

- hypoblast (face yolk sac)

After:

- ectoderm (face amniotic sac)

- mesoderm

- endoderm (face yolk sac)

Front 171

Describe medial, lateral sides and core of the neural folds

Back 171

- Neuroectoderm medially

- non-neural (surface) ectoderm laterally

- Neural crest cells at the apices

- mesoderm in core

Front 172

Primitive midgut

Back 172

During transverse folding, the endoderm in the middle of the embryo is rolled into aprimitive midgut.

The primitive midgut remains connected to the remains of the yolk sac by the vitelline duct(yolk stalk).

Front 173

4 Causes of birth defects

Back 173

1. Chromosomal abnormality

- aneuploidy

- structural abnormalities (alter chromosome segments)

2. Mutations

3. Environmental factors

- maternal infections

- physical factors

- chemical factors

- mechanical factors

- maternal factors

4. Multifactorial causation: combination of multigenetic and environmental factors

Front 174

5 Principles of Teratology

Back 174

1. malformation depends on genotype and how the genotype interacts with the environment.

2. susceptibility to malformation varies depending on developmental stage

3. access of the adverse influence to developing tissues depends on the nature of the influence.

4. Four deviations (death, malformation, growth retardation and functional defect)

5. manifestation of deviant development increases in frequency and degree as dosage increases

Front 175

Clusters of malformations

Back 175

If a fetus has one defect then it will most likely have other defects associated with it too.

Front 176

Describe the mesenteries of the primitive gut.

Back 176

Foregut: Ventral + dorsal mesentery

Midgut + Hindgut: only dorsal mesentery

Front 177

3 Abnormalities of Midgut Development

Back 177

- malrotation

- omphalocele

- gastroschisis

Front 178

What does the rectoanal canal contribute to the formation of?

What is developed from the proctodeum?

Back 178

Rectoanal canal ---> rectum and upper part of anal canal

Proctodeum ---> distal part of the anal canal

Front 179

What does the cloacal membrane become after the urorectal septum divides it?

Back 179

Urogenital and anal membranes

Front 180

What initiates the development of the liver, gall bladder and pancreas?

Back 180

FGF from the cardiac mesoderm signal the endoderm on the distal part of the foregut to grow out.

Front 181

Where do the hepatic sinusoids andstroma (supporting connective tissue), the capsule of the liver, the lesser omentum, and thefalciform, triangular and coronary ligaments all arise from?

Back 181

- attenuation of the mesoderm in the ventral mesentery as the liver grows

Front 182

What are the two buds that form from the distal part of the forgut under FGF?

Back 182

- dorsal pancreatic bud (into d. mesentery)

- liver, gall bladder, and ventral pancreatic duct (into v. mesentery)

Front 183

What are some consequences of obstruction of the bowel?

Back 183

- Distension proximal to level of obstruction

- reduced stool

- reflux

- polyhydramnios

Front 184

What are the general steps for the formation of the laryngotracheal diverticulum?

Back 184

- endoderm lining of foregut makes a groove: laryngotracheal diverticulum

- diverticulum pinch inwards to create tracheosophageal ridges

- ridges fuse to create tracheoesophogeal septum

Front 185

True or false:

Pain sensory fibres do not innervate the visceral pleura but they do innervate theparietal pleura.

2. Where are the visceral and parietal pleuras continuous with each other?

Back 185

1. True

2. The root of the lung(where the bronchi and vessels enter into the lung from the mediastinum)

Front 186

Pronephric phase (3rd week)

Back 186

- vesicles from nephrogenic cord (derived intermediate mesoderm) form pronephric duct

- at cervical segments

- caudal tip grows and opens into cloaca

- pronephric part of nephrogenic cord and duct degenerate.

- remaining pronephric duct is called mesonephric duct

Front 187

Mesonephric phase (4th week)

Back 187

- thoracic and lumbar segments

- mesonephric tubules form and fuse with mesonephric duct

- mesonephros degenerates

Front 188

What happens in the Metanephric phase (5th week)

Back 188

- ureteric bud outgrows from mesonephric duct

- GDNF released from metanephric mass of mesoderm

- ureteric bud grows into the mass and releases growth factors to maintain the mass

Front 189

During the 4th week of development where can the Primodial Germ cells be found?

Where do they migrate to next and what do they stimulate?

Back 189

- the yolk sac near the origin of the allantois

- by 6th week enter sex cords

- stimulate the further development of gonads

Front 190

What happens to these structures in males?

Back 190

- genital tubercle elongates

- urogenital folds get pulled along with urogenital groove in between

- glandular plate forms by ingrowth of epithelium on the genital tubercle ---> glans penis

- urogenital folds ---fuse---> penile urethra

- labiosacral swellings ---> scrotum

Front 191

hypospadias

Back 191

Condition where the urethra is on underside of penis (urogenital folds did not fuse properly)

Front 192

1. What is the name of the mesoderm that forms the developing heart?

2. What does this mesoderm develop into?

Back 192

1. Cardiogenic mesoderm

- migrates cranially past the neural plate and oropharyngeal membrane.

2. Primary heart fields, which migrates even more crainially to the cardiac crescent

Front 193

Through what process do the primordial chambers of the heart develop?

Back 193

Pre-looping

- Sinus Venosus and primitive atrium will be on the caudal end

- Truncus leading to the two aortic arches is on the cranial end.

Front 194

Through what process do the primordial chambers of the heart develop with an apex to the left (levocardia), RV rotated anteriorly and 3D geometry for further development?

Back 194

Dextra-looping (to the right)

Front 195

Compare the right and left atria

Where are they derived from?

Back 195

right: conical, triangular and broad

left: elongated, serpiginous, with a scalloped lower border

Primitive atrium

Front 196

1. What are atrial appendages derived from and what are they a good clue to?

2. What happens to the primary pulmonary vein?

Back 196

1. Primitive atrium. Sidedness on the body

2. shortens and disappears so that the pulmonary vein feed directly into the primitive atrium.

Front 197

1. What is the name of the first gap in the developing septum primum?

2. What is the name of the second hole formed and what is the significance of this hole?

Back 197

1. Ostium primum

2. Ostium secundum, allows to bypass the ventricles and lungs since in the developing heart receives oxygenated blood via the umbilical vein from the placenta to the right atrium.

Front 198

What layer covers the ostium primum?

What does the foramen ovale become when this layer fuses with the septum primum?

Back 198

Septum secundum

Fossa Ovalis

Front 199

What develops in the Atriventricular junction?

What separates the common AV orifice into right and left AV junctions?

Back 199

The tricuspid (right) and mitral (left) atroventricular valves develop in the junction.

The separation is by endocardial cushions

- mediated by neural crest cells

Front 200

What three things need to come together to separate the left and right ventricles?

Back 200

muscular wall, endocardial cushion, wall septum

Front 201

The division of the truncus is formed by?

Back 201

Spiral septum, which separates the pulmonary artery from the aorta.
- mediated by neural crest cells

Front 202

What happens to the mesenchymal cells during the formation of a somite?

Back 202

They become polarized and acquire epithelial characteristics:
- elongate and orient around the myocoele (central cavity)
- develop apical junction complexes with tight junctions
- basement membrane

Front 203

What does the somite break up into?

Back 203

- ventromedial somite ---> sclerotome

- dorsolateral aspect ---> dermomyotome + myotome

Front 204

What does the myotome portion of the somite split into and what do these portions contribute to the development of?

Back 204

- dorsal (epaxial) myotome ---> back muscles

- ventral (hypaxial) myotome ---> muscles of trunk and limbs

Front 205

What is the name of the remaining portion of the somite once the dermomyotome, myotome and sclerotome dissociate?

What does this portion develop into?

Back 205

Dermatome

- the dermatome cells re-acquire their mesenchymal phenotype and mix with the somatic layer of the lateral plate mesoderm to form the dermis

Front 206

True or False:

The polarization and differentiation of the somite is not controlled by signals from adjacent tissues

Back 206

False.

During the breakup of the somite, the development and differentiation of its components is determined by positional cues in the form of secreted molecules from the notochord and ventral neural tube, the dorsal neural tube and the epidermis and the intermediate mesoderm.

Front 207

Where will the sclerotome cells migrate to and what will each migrated portion form?

Back 207

1. Ventromedially to surround the notochord. ---> vertebral bodies and intervertebral discs.

2. Dorsomedially between the neural tube and the surface ectoderm. ---> neural arches ofthe vertebrae and the meninges around the spinal cord. (spina bifida)

3. Ventrolaterally to form the costal processes. The costal processes ---> transverse processes of the vertebrae. In the thoracic region ---> the ribs

Front 208

What forms the annulus fibrosis, nucleus pulposis and bodies of the vertebrae?

Back 208

cellular middle portions of each sclerotome pair ---> annulus fibrosis

notochord ---> nucleus pulposus

intermingling of caudal/cranial ends of somite pairs ---> vertebral body

Key point: Discs are segmental, Vertebrae are intersegmental

Front 209

1. Hemivertebra

2. Klippel Feil syndrome

Back 209

Defects of Sclerotome Development:

1. only half the vertebra forms. Thesclerotome cells of the caudal part of one somite pair failed to intermingle withthe cells of the cranial part of the following pair on half the vertebrae.

2. fusion of vertebrae

Front 210

What are the different types of spina bifida?

Back 210

Spina bifida = gap in the vertebral arch of a vertebra.

- spinal cord and vertebrae may get involved secondary to the defect in vertebral and neural tube formation, respectively.

Front 211

Spina Bifida:

1. Spina Bifida Occulta

2. Meningocele

3. Meningomyelocele

Back 211

These defects result from abnormal formation of thevertebral arch.

1. most common, asymptomatic

2. Accumulation of CSF in the meningeal spaces surrounding the spinal cord

3. If in meningocele the cord is also herniated, thecondition is called meningomyelocele.

Front 212

Spina Bifida:

1. Myeloschisis

2. Myelomeningocele

Back 212

1. open spinal cord (neural plate)

- paralysis

- failure of neural tube to close (therefore vertebra also can't close).

- causes Hydrocephalus

2. CSF accumulates in meningeal space and elevates the neural plate producing a sac. The covering of the sac = neural plate

Front 213

What is FGF 10 expression responsible for and how is it triggered?

Back 213

Somitic/paraxial mesoderm triggers FGF 10 expression in the adjacent lateral plate mesoderm.

- this induces the Apical Ectodermal Ridge (AER) between the dorsal and ventral ectoderm.

Front 214

What does the AER stimulate in the underlying lateral plate mesoderm?

Back 214

- rapid proliferation, creating the progress zone in the developing limb.
- this forms a self-differentiating system
- first cells to leave the progress zone form the proximal limb.

Front 215

What is responsible for the interdigital tissues removal/apoptosis between the digits?

Back 215

BMP expression

Front 216

How is the craniocaudal organization of the limbs determined?

Back 216

Determined by small area of mesoderm in the caudal part of the limb bud – the Zone of Polarizing Activity (ZPA)

- this is in the postaxial mesoderm

- identity is formed according to signal strength

Front 217

Where are bone, cartilage and muscles derived from for the limb?

Back 217

- Bone and Cartilage is derived from the somatic layer of lateral plate mesoderm

- Skeletal muscle is derived from myoblasts that migrate in from the hypaxial part of the somite myotomes.

Front 218

The limbs have a dorsal (extensor) and a ventral (flexor) surface related to the expression of?

What represses the expression of this?

Back 218

Wnt 7a in the ectoderm on the dorsal side of the limb bud

Engrailed (En-1) expression in the ventral ectoderm represses Wnt 7a expression and limits its area of influence

Front 219

What is the Oropharyngeal membrane and what appears here at the 4th week of development?

Back 219

- membrane at rostral end where the ectoderm and endoderm are in direct contact.

- frontonasal prominence and the pharyngeal arches appear at 4th week

Front 220

What causes the frontonasal prominence?

What do the embryonic tissue found in the prominence develop into?

Back 220

proliferation of mesoderm cells and arrival of neural crest cells

- mesoderm ---> skeletal muscle cells and endothelium of blood vessels

- neural crest cells ---> bone and connective tissue of the face, sensory and autonomic ganglia of head and neck

mesoderm + neural crest cells ---> mesenchyme. The neural crest cells contribute mainly to the mesenchyme in the ventral parts of the pharyngeal arches and therefore contribute to the face.

Front 221

What does each pharyngeal arch contain?

Back 221

- An artery
- Cartilage
- Muscle
- A nerve
-- 1st arch: trigeminal
-- 2nd arch: facial
-- 3rd arch: glossopharyngeal
-- 4th arch: vagus

Front 222

What does the first pharyngeal arch divide into?

Back 222

- Maxillary and mandibular prominences

Front 223

The ophthalmic division of the trigeminal nerve (V1) grows into the _____________ , the maxillary division (V2) into the _____________ , and the mandibular division (V3) into the_______________.

Back 223

frontonasal prominence
maxillary prominence
mandibular prominence

Front 224

The oropharyngeal membrane disappears in the 4th week so that the stomatodeum opens up into the pharynx.

What are the stomatodeum and pharynx lined with?

Back 224

Stomatodeum is lined with ectoderm

Pharynx with endoderm

Front 225

The face and palate develop from?

Back 225

The frontonasal prominence and the first pharyngeal arches.

Front 226

What structures form on the ventrolateral frontonasal prominence?

Back 226

Olfactory placodes ---> nasal pits ---> medial and lateral nasal prominences with an olfactory pit in between.

Front 227

What separates the olfactory pit from the oral cavity?

When does this structure separating the two disappear?

Back 227

oronasal membrane

disappears at 7th week

Front 228

1. The mandibular prominences will merge to form the?

2. The medial nasal prominences will merge with each other to form the?

Back 228

1. lower jaw

2. philtrum of the upper lip and the primary palate (premaxilla – the part that holds the upper incisor teeth).

Front 229

Nasal fin

Back 229

- Found between the medial nasal prominences and the maxillary prominences.

- It will break down and the mesenchyme in the cores of each will merge together to complete the continuity of the upper lip.

Front 230

What is the nasolacrimal groove and what forms from it?

Back 230

It separates the maxillary and lateral nasal prominences.

- ectoderm of groove's floor forms a cord, which canalizes to form the nasolacrimal duct (connects lacrimal sac to inferior meatus of nasal cavity)

Front 231

What will each develop into?

1. Frontonasal prominence

2. Medial nasal prominence

3. Lateral nasal prominence

Back 231

1. Frontonasal prominence – forehead, nasal bridge, nasal septum

2. Medial nasal prominence – primary palate, philtrum of upper lip, tip of the nasalseptum (columella)

3. Lateral nasal prominence – ala of the nose

Front 232

What will each develop into?

1. Maxillary prominence

2. Mandibular prominence

Back 232

1. Maxillary prominence – maxillae (exclusive of the primary palate) and lateral part ofupper lip

2. Mandibular prominence – lower lip and jaw

Front 233

What are the 2 main sources that develop the palate?

Back 233

- The medial nasal prominences form the primary palate

- The palatal process of the maxillae form the secondary palate, including the soft palate and the uvula.

Front 234

During the 7th and 8th week, what do the palatal processes fuse with?

In what direction does this fusion take place?

Back 234

The palatal processes fuse with each other, with the primary palate, and with the nasal septum.

Breakdown of the epithelial seams (fusion) between the shelves begins anteriorly and proceeds in a posterior direction. (establishment of mesenchymal continuity).

Front 235

Pharyngeal pouches

Pharyngeal grooves

Back 235

Valleys in between pharyngeal arches.

Pouches are inside (lined with endoderm).

Grooves are outside (lined with ectoderm).

Front 236

What is the fate of the first pharyngeal groove and the ectoderm at the bottom of this groove?

Back 236

- 1st groove deepens ---> external auditory meatus

- the ectoderm at the bottom of the groove becomes the external surface of tympanic membrane

Front 237

What is a cyst found on the medial/anterior border of the sternocleidomastoid is probably a remanent of?

Back 237

The cervical sinus (created by the second pharyngeal arch)

Front 238

What happens to the pharyngeal grooves (Except for the first groove)?

Back 238

The second arch grows caudally and covers the other arches. A cervical sinus is created. Ectoderm-lined. This sinus can later become a cyst on the sternocleidomastoid.

Front 239

What happens to the first pharyngeal pouch?

What does the 2nd pouch form?

Back 239

- deepens and meets floor of 1st pharyngeal groove
- forms middle ear and auditory tube

- 2nd pouch ---> tonsillar fossa (the depression between the palatoglossal and palatopharyngeal arches occupied by the palatine tonsil)

Front 240

The ear drum separating the middle ear and the external auditory meatus is derived from?

Back 240

The endoderm of the first pharyngealpouch and the ectoderm of the first pharyngeal groove.

Front 241

What happens to the 3rd pharyngeal pouch?

What does the 4th pouch form?

Back 241

Third pouch – The cells in the ventral part of each pouch cells migrate into theanterior mediastinum to form the thymus. Cells from the dorsal part of each pouchmigrate into the neck forming the inferior parathyroid glands

Fourth pouch – cells from the dorsal part migrate into the neck to form thesuperior parathyroids and cells in the ventral part invade the thyroid gland to formthe parafollicular (thyrocalcitonin - secreting) cells.

Front 242

What cartilages do the 4 pharyngeal arches form?

Back 242

First arch (Meckle's cartilage) – the mandible, sphenomandibular ligament,malleus and incus

Second arch (Reichert's cartilage) – the stapes, styloid process of temporal bone,lesser horn and part of the body of the hyoid

Third arch – the greater horn and part of the body of the hyoid

Remaining arches – laryngeal cartilages

Front 243

What muscles do the 4 pharyngeal arches form?

Back 243

First arch – muscles of mastication, mylohyoid, anterior belly of digastric, tensortympani and tensor palati (innervated by V)

Second arch – muscles of facial expression, posterior belly of the digastric,stylohyoid and stapedius (innervated by VII).

Third arch – stylopharyngeus (innervated by IX)

Remaining arches – levator palati, muscles of the pharynx and the larynx(innervated by X).

Front 244

1. Truncus arteriosus

2. Aortic sac

Back 244

1. Gives rise to

- pulmonary trunk artery

- Ascending aorta

2. Connects the Truncus arterosus with the aortic arches, which develop into the arteries in the chest and neck.

Front 245

How does the thyroid gland develop?

Back 245

Finger like invagintion at foramen cecum between 1st and 2nd arch, thyroglossal duct, grows down.

The distal part expands to form lobes of the thyroid. Proximal part disappears.

- If they do not disappear then remnants like the pyramidal lobes of thyroid can be found.

Front 246

Thyroglossal duct cyst

Back 246

Ectopic thyroid tissue can sometimes enlarge.

Front 247

How does the pituitary gland (adenohypophysis) develop?

Back 247

- from the ectoderm of the roof of the stomatodeum.

- The neurohypophysis (posterior lobe) develops as a downgrowth neuroectoderm (blue) of the neuraltube in the region of the developing hypothalalmus.

Front 248

Describe the development of the tongue

Back 248

Lateral lingual swellings ---> Anterior 2/3 from 1st arch – trigeminal nerve

- VII will contribute taste to anterior 2/3

Posterior 1/3 from 3rd and 4th arches (glossopharyngeal and vagus)

Skeletal muscle migrates in from the occipital somites (Hypoglossal)

Front 249

From the venous (caudal) pole to the arterial (cranial) pole what are the primitive chambers and what do they develop?

Back 249

‐ Primitive atrium (will give rise to both left and right atria)

‐ Primitive ventricle (will give rise to LV)

‐ Bulbus cordis (will give rise to RV)

‐ Truncus (the main outflow, which will split into aorta and pulmonary artery)