Embryology Minimals

Front 1

Describe the sequence of oogenesis.

Back 1

1. oogonium,
2. profase of 1st meiotic division: primary oocyte,
3. completion of 1st meiotic division: secondary oocyte and first polar body
4. completion of the second meiotic division: second polar body and definitive oocyte,
5. third and fourth polar bodies.

Front 2

Name the stages of development of the ovarian follicle in sequence! Make a drawing of the Graafian follicle, and label the major parts!

Back 2

• Primordial, primary, secondary (growing), tertiary or vesicular follicle.
1. Theca externa
2. Theca interna
3. Follicular antrum with fluid
4. Cumulus oophorus
5. Corona radiata
6. Membrana granulosa
7. Oocyte
8. Zona pellucida

Front 3

Define the term "spermiogenesis". Describe the spermatogenesis in sequence. Draw a mature spermium and label parts!

Back 3

• Spermiogenesis: formation of spermatozoa from spermatid.
• sequence of spermatogenesis: spermatogonium, primary spermatocyte, secondary spermatocyte, spermatid.
1. Head
2. Neck
3. Middle piece
4. Principal piece
5. End piece

Front 4

Which cells of spermatogenesis are isolated from the blood-born antigens by the blood-testis barrier?

Back 4

• late primary spermatocytes
• Secondary spermatocytes
• Spermatids
• Sperm cells (spermatozoa)

Front 5

What is meant by the "ovarian cycle"?

Back 5

• Development of follicles, ovulation, formation and subsequent regression of corpus luteum.

Front 6

Define the approximate date of ovulation and describe the hormonal background!

Back 6

• Around midcycle (14 days) under the influence of FSH and LH, triggered by a surge of LH production.

Front 7

What is the fate of matured ovarian follicle?

Back 7

1. Release of the oocyte by rupture of the follicle: ovulation
2. The collapsed wall of the follicle surrounds a central clot of retained blood and follicular fluid. This is the corpus hemorrhagicum. From the granulosa cells the granulosa luteal, and from the theca interna cells the theca luteal cells develop respectively.
3. In case of pregnancy, the corpus luteum further develops and forms the persisting corpus luteum, otherwise it degenerates and becomes the corpus albicans.
4. Matured, but undischarged follicles undergo degeneration resulting in atretic follicles.

Front 8

From which structure does the corpus luteum develop, and what does it secrete ?

Back 8

• From corpus hemorrhagicum, by proliferation of theca interna, and granulosa sells.
• Progesteron and oesrtogen

Front 9

Describe the processes that make the spermatozoa capable of fertilising the oocyte!

Back 9

• Epididymal maturation: changes in metabolism, acquiring the capability for movement.
• Capacitation: a glycoprotein coat and seminal plasma proteins are removed from the plasma membrane that overlies the acrosomal region of the spermatozoa.
• Acrosomal reaction: Release of enzymes from the acrosome: a) hyaluronidase; b) proteolitic enzymes.

Front 10

Name the phases of fertilisation and describe the reactions of the fertilised oocyte.

Back 10

1. Penetration of the corona radiata
2. Penetration of zona pellucida
3. Fusion of oocyte - sperm cell membranes
4. The spermatozoon (except for the cell membrane) enters the cytoplasm of the oocyte.
• Reactions of the egg: cortical and zonal reaction; resumption of the second meiotic division; metabolic activation of the egg.

Front 11

What is meant by cleavage and blastocyst formation?

Back 11

• Cleavage: Formation of morula and then the blastocyst by mitotic divisions of fertilized ovum.
• Blastocyst formation: fluid begins to penetrate into the intercellular spaces of the inner cell mass. The spaces become confluent and a single cavity, the blastocele is formed: the blastocyst.

Front 12

Make a schematic drawing of the early blastocyst and label its major parts!

Back 12

1. Blastocyst cavity
2. Outer cell mass or trophoblast
3. Inner cell mass or embryoblast

Hint 12

Picutre!

Front 13

How does the endometrium change during the menstrual cycle?

Back 13

• Stages of the menstrual cycle:
1. Menstrual phase: rupture of blood vessels and detachment of the functional layer of the endometrium.
2. Regeneration phase: regeneration of the functional layer
3. Proliferative phase (follicular or estrogenic stage): gradual growth of the endometrium.
4. Secretory (luteal ) phase: development of the compact and spongy layers in the functional layer. Secretory activity of glands, decidual reaction of stroma cells, formation of coiled arteries within the endometrium, edema in the stroma.
5. Regression: temporary contraction of coiled arteries resulting in ischaemia of the endometrium. Consecutive dilatation of vessels followed by hyperemia of the endometrium.

Front 14

Where is the preferred site of implantation? List few abnormal implantation sites!

Back 14

• Normal: Along the posterior. and anterior. wall of the body of the uterus, between the openings of the glands.
• Abnormal: close to the internal os of the uterus; outside the uterus (extrauterine or ectopic pregnancy): any place of the abdominal cavity, ovary, uterine tube.

Front 15

Name those parts of the drawing, which are indicated by arrow.

Back 15

1. Syncytiotrophoblast with lacunae
2. Cytotrophoblast
3. Amnionic cavity
4. Epiblast (Ectoderm)
5. Hypoblast (Endoderm)
6. Exocoelomic cavity (primitive yolk sac)
7. Exocoelomic (Heuser's) membrane

Hint 15

Picture

Front 16

What is the difference between syncytiotro-phoblast and cytotrophoblast?

Back 16

• Cytotrophoblast: mononucleated cells that form the inner layer of trophoblast (Langhans cell layer).
• Syncytiotrophoblast: outer multinucleated zone of trophoblast without distinct cell boundaries.

Front 17

What is the role of syncytiotrophoblast during implantation?

Back 17

• Secretion of proteolytic enzymes which erode the endometrial epithelium and the stroma of the endometrium, so that the blastula can penetrate, and get implanted in the endometrium.

Front 18

What is the difference between the extraembryonic and intraembryonic mesoderm? Where do they originate from?

Back 18

• Extraembryonic mesoderm: derives from the trophoblast and form a fine, loose connective tissue, which is located outside the embryo.
• Intraembryonic mesoderm: the third germ layer between the epiblast and hypoblast layers. Origin: epiblast.

Front 19

List the components of the extraembryonic mesoderm.

Back 19

1. Somatopleuric mesoderm
2. Splanchnopleuric mesoderm
3. Connecting stalk
4. Chorionic mesoderm

Front 20

What is the connecting stalk and how does it develop further?

Back 20

• Part of the extraembryonic mesoderm containing the allantois, vitelline duct, as well as the umbilical and vitelline vessels.
• Later the amnion envelops the connecting stalk and the yolk sac stalk with their vessels, forming the primitive umbilical cord.

Front 21

From which germ disk does the blood, lens of eye, epithelium of kidney tubules, and thymus develops?

Back 21

a)Blood - mesoderm
b) Lens of eye - ectoderm
c) Kidney tubules - mesoderm
d) Thymus - endoderm

Front 22

From which germ disk does the bone, hypophysis, chief cells of the parathyroid glands and the thyroid glands develop?

Back 22

a) bone - mesoderm
b) hypophysis - ectoderm
c) chief cells of the parathyroid gland – placod plate
d) thyroid gland - endoderm

Front 23

Make a schematic drawing illustrating the dorsal view of a 16-day old embryo! Label parts!

Back 23

1. Prochordal plate
2. Notochordal process
3. Primitive streak
4. Primitive node
5. Future cloacal membrane
6. Ectoderm

Front 24

Make a schematic drawing illustrating the transverse section of the trilaminar germ disc at the cephalic part of an 18-day-old embryo! Label parts!

Back 24

1. mesoderm
2. notochord
3. ectoderm.
4. entoderm
5. yolk sac

Front 25

Make a schematic drawing illustrating the transverse section of the trilaminar germ disc at the cephalic part of an 18-day-old embryo! Label parts!

Back 25

1. mesoderm
2. notochord
3. ectoderm.
4. entoderm
1. yolk sac

Front 26

What is the notochord and the primitive pit? Indicate its place in a schematic drawing showing the midsagittal section of the 16-day-old embryo!

Back 26

• At the cephalic end of the primitive streak the primitive node develops. The primitive pit develops from the primitive node by cell-invagination. These cells migrate straightforward towards the cephalic end, and form a tube - like process: the notochordal or head process. The canal of the head process is the cranial extension of the primitive pit. The dorsal wall of the notochordal process proliferates and forms the definitive notochord.
1. amnionic cavity
2. ectoderm (epiblast)
3. primitive pit
4. prochordal plate
5. notochordal process
6. primitive streak
7. allantois
8. yolk sac

Front 27

What is the neural plate? What is meant by neural induction?

Back 27

• Thickening of the ectoderm, primordium of the nervous system. The notochord has an inductive influence on the ectoderm, resulting in the formation of the neural plate.

Front 28

What is the "placode" and what are its derivatives?

Back 28

• Placode: thickenings of the surface ectoderm at the head region of the embryo.
a) Hypophyseal placode (I): Rathke's pouch. (adenohypophysis)
b) Nasal placode (2): olfactory epithelium.
c) Lens placode (2): lens of eye
d) Trigeminal placode (2): semilunar ggl.
e) Acoustic placode (2): sensory epithelium of vestibular and cochlear receptors, ganglions.
f) Epibranchial placode (2): sensory epithelium of taste buds.
g) Branchial: placode (2): sensory ganglia of VIIth, IXth, Xth cranial nerves.

Front 29

What are the derivatives of the paraxial, intermediate and the lateral plate of mesoderm?

Back 29

• Paraxial mesoderm: breaks up into blocks of somites, and somitomers at the cephalic region. The somites differentiate into sclerotom, dermatome, myotome.
• Intermediate: in the cervical and upper thoracic region it gives rise to the nephrotomes. Caudally the nephrogenic cord develops from it.
• Lateral plate: somatic or parietal mesoderm layer, splanchnic or visceral mesoderm layer, intraembryonic celomic cavity.

Front 30

What is meant by the a) cephalo-caudal and b) lateral foldings of the embryo?

Back 30

• Folding of a flat trilaminar embryonic disc into a somewhat cylindrical embryo.
a) Cephalo-caudal fold: Cranially, the developing forebrain grows beyond the buccopharyngeal membrane and overhangs the developing heart. Caudally the tail region projects over the cloacal membrane.
b) Lateral/transverse folds: Each lateral body wall folds towards the median plane in a ventral direction.

Front 31

Make a simple drawing to demonstrate the primitive gut in a 4-week-old embryo! Label parts!

Back 31

1. Pharyngeal gut,
2. tracheobronchial diverticulum,
3. esophagus,
4. stomach,
5. pancreas,
6. liver,
7. gallbladder,
8. vitelline duct,
9. allantois,
10. cloaca,
11. primitive intestinal loop,
12. hindgut,
13. cloacal and
14. buccopharyngeal membrane.

Front 32

What are the fetal membranes?

Back 32

• Amnion, chorion, decidua parietalis and capsularis

Front 33

List and characterize the different developmental stages of the placental villi!

Back 33

a)Primary villi : cyto- and syncytiotrophoblast cells
b) Secondary villi: cyto- and syncytiotrophoblast cells + extraembryonic mesoderm in the centre of villi
c) Early tertiary villi: blood vessels in the mesoderm layer + the layers of the secondary villi.
d) Late tertiary villi: the cytotrophoblast partially disappears, and the syncytium and the endothelial wall of the blood vessels may be in direct contact. Villi form richly arborizing tree-like structure.

Front 34

List the separating layers between fetal and maternal blood in the early and the matured placenta!

Back 34

• Early: syncytiotrophoblast, cytotrophoblast, trophoblast basement membrane, connective tissue, capillary basement membrane, endothelium
• Late: syncytiotrophoblast, trophoblast basement membrane, capillary basement membrane, and endothelium. Some connective tissue may be present between the two basement membranes.

Front 35

Define the term of decidua! Name its parts in relation to the implanted embryo!

Back 35

• Decidua: Functional layer of the gravid endometrium.
1. Decidua basalis: between the chorion frondosum and myometrium. Primordium of placenta materna.
2. Decidua capsularis: over the abembryonic pole.
3. Decidua parietalis: rest of the decidua, except the basalis and capsularis.

Front 36

Describe the parts of the full term placenta!

Back 36

1. Fetal portion: chorionic plate, chorion villi.
2. Maternal portion: decidua basalis.

Front 37

Name the layers of the chorionic plate!

Back 37

1. amnionic epithelium
2. central mesoderm
3. chorionic mesoderm
4. trophoblasts (syncytio-, and cyto-)

Front 38

Define the term of cotyledon!

Back 38

• The compartments of the placenta, partially separated by the decidual septa, each cotyledon consists of one or more stem villi surrounded by maternal blood.

Front 39

List the functions of placenta !

Back 39

1. Transport and exchange of gases, nutrients, waste products,
2. Transport of antibodies to fetus,
3. Endocrine function,
4. Mechanical protection,
5. Barrier for some germs and drugs.

Front 40

List the hormones that are produced by the placenta!

Back 40

• Progesteron, estrogenic hormones, human chorionic gonadotropins (hCG),human chorionic somatotropin (hCS), human chorionic thyreotropin (hCT), relaxin, human chorionic adreno-corticotropin (hCACTH).

Front 41

What is the difference in the composition of the primitive and matured umbilical cord?

Back 41

• Contents of primitive cord: the connecting stalk that contains allantois, umbilical vessels consisting of two arteries and two veins, yolk sac stalk accompanied by the vitelline vessels.
• Contents of the matured cord: two umbilical arteries, one umbilical vein, Wharton's jelly.

Front 42

What are the names of the blood vessels of mature umbilical cord? Which of them transport oxigenated blood?

Back 42

• two umbilical arteries,
• one umblical vein. The vein transports oxigenated blood.

Front 43

List signs of maturity of a newborn!

Back 43

• weight : above 2500 gr,
• nipples are protruding out from the skin,
• nails extend beyond finger tips,
• testes are in scrotum,
• labia majora covers labia minora,
• forehead-hair border evident.

Front 44

List the most common types of twin formation and characterize the relationship of placentas and the fetal membranes of the twins!

Back 44

a) Monozygotic or identical twins:
i) with separate placenta, amnion and chorion.
ii) common placenta and chorion, separate amnionic cavities.
iii) common placenta, chorion and amnionic cavity.
b) Dizygotic or fraternal twins:

i) separate placenta, separate chorion, separate amnion.
ii) separate placenta and amnion, fused chorion.

Front 45

Define the fontanels of the newborn skull! Describe their positions related to the bones of the skull!

Back 45

• Anterior, posterior, anterolateral or sphenoid, posterolateral or mastoid fontanels.
1. Anterior: where the two parietal and frontal bones meet.
2. Posterior: where the occipital and two parietal bones meet.
3. Anterolateral: where the parietal, frontal, temporal and sphenoid bones meet
4. Posterolateral: where the occipital, parietal, temporal bones meet.

Front 46

Draw the superior aspect of the calvaria of newborn, and label the fontanels, sutures and the bones!

Back 46

1. Frontal bone
2. Occipital bone
3. Parietal bone
4. Anterior (or frontal) fontanel
5. Posterior (or occipital) fontanel
6. Coronal suture
7. Sagittal suture
8. Lambdoid suture

Front 47

Which bones develop from the chondrocranium?

Back 47

Which bones develop from the chondrocranium?
• Occipital bone (except the upper portion of squamous part), petrous and mastoid parts of temporal bone, sphenoid bone (except the medial plate of the pterygoid process), ethmoid bone.

Front 48

Which bones develop from the viscerocranium?

Back 48

• Maxilla, mandible, zygomatic bone, squamous and tympanic parts of temporal bone, styloid process of temporal bone, nasal bone, lacrimal bone, vomer, hyoid bone, inf. concha, medial plate of the pterygoid process of the sphenoid bone, palatine bone.

Front 49

What is meant by the rearrangement of the sclerotomes in development of the vertebral column?

Back 49

• The caudal half of each cranial sclerotom proliferates, proceeds into the subjacent tissue and joins the cephalic part of the subjacent sclerotom. The fused halves of the adjacent sclerotomes with the incorporated intervertebral tissue form the cartilaginous vertebral body that becomes intersegmental in origin.

Front 50

Describe the malformation called "spina bifida"!

Back 50

• Imperfect fusion or nonunion of the vertebral arches

Front 51

Into which parts can the intraembryonic celomic cavity be divided in the 4th embryonic week?

Back 51

• Pericardial cavity, pleuroperitoneal canal, peritoneal cavity.