Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HBSF Block 1 > Embryology Lecture 3 Weeks 2 and 3 > Flashcards

Embryology Lecture 3 Weeks 2 and 3 Flashcards

1
Q

In week 2:

The implanted embryo becomes more ______ in the endometrium

Further development of _______ into the placenta

Development of a ______, ______, and _______

A

deeply implanted

trophoblast

bilaminar embryo, amniotic cavity and yolk sac

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What happens during bilaminar disc formation?

A

Trophoblast further differentiates and invades into maternal tissue:

Cytotrophoblast: stem cell population for the placenta

Syncytiotrophoblast: Invasive, fused cells. Derived from cytotrophoblast

Breaks maternal capillaries, trophoblastic lacunae then fill with maternal blood

Secretes human chorionic gonadotropin (hCG)

8.5.6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How does the bilaminar disc form in day 8?

A

¨Epiblast contributes to forming the overlying amniotic membrane and amniotic cavity (columnar)

¨Hypoblast contributes to forming the underlying primitive yolk sac/exocelomic cavity (cuboidal)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Cells derived from the primitive yolk sac cells (hypoblast cells) form a fine, loose connective tissue called _______

Spaces appear in extraembryonic mesoderm, coalesce to form ______

Chorionic cavity surrounds whole part of embryo except where the embryo is attached to the cytotrophoblast by ______

A

extraembryonic mesoderm

extraembryonic coelom (chorionic cavity)

connecting stalk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The extraembryonic mesoderm now has 2 components, what are they?

A

lining the cytotrophoblast and amnion:

extraembryonic somatic mesoderm

covering the yolk sac:

extraembryonic splanchnic membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the 3 main events of Day 13

A

Formation of chorion and primary chorionic villi

Formation of chorionic cavity

Formation of the definitive yolk sac

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

¨Cytotrophoblasts proliferate into the syncytiotrophoblast and form ______

Exocoelomic cavity (primitive yolk sac) lined by new hypoblast cells gets replaced with a ______

Some of hypoblast cells near future mouth proliferate and form ______

A

primary chorionic villi

smaller definitive yolk sac or the secondary yolk sac

anterior visceral endoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The ___ is formed by the extraembryonic mesoderm

A

connecting stalk

Note: The extraembryonic coelom expands to form a large cavity, within which the embryo and the attached amniotic cavity and yolk sac are suspended by the body stalk (connecting stalk) from which the umbilical cord forms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The posterior wall of the yolk sac forms a small diverticulum which is called ______ and extends into the connecting stalk

A

allantois

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Summary of Week 2 events

A

Embryoblast forms 2 layers

§Epiblast

§Hypoblast

Trophoblast differentiates into 2 layers

§Cytotrophoblast

§Syncytiotrophoblast

Extraembryonic mesoderm splits into 2 layers

§Somatic

§Visceral

2 cavities form

§Amniotic cavity

§Chorionic cavity

Appearance of primary chorionic villi

Anterior visceral endoderm

Establishment of cranio-caudal axis of development

Completion of implantation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What can low hCG or high hCG mean during early pregnancy?

A

Low hCG may predict a spontaneous abortion or may indicate an ectopic pregnancy

High hCG may indicate a multiple pregnancy, hydatidiform mole, or gestational trophoblastic neoplasia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

____ is marked benign enlargement of chorionic villi (trophoblast) and is characterized by grapelike vesicles in uterus and absence of embryo, high hCG level.

A

Hydatidiform Mole

Gestational trophoblastic neoplasia (choriocarcinoma)

Malignant tumor of trophoblast

Some times they metastasize to liver and other organs (prognosis poor)

8.5.6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is paternal imprinting during hydatiform mole?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the 7 main events that occur during week 3 of embryo development?

A

Bi-laminar germ disc forms the primitive streak

Gastrulation forms tri-laminar embryo

Neurulation or neural induction takes place

Somites are formed

Left-right asymmetry is determined

Cardiovascular development takes place

Extraembryonic spaces (coelom) and primitive placenta (villi) further develop

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do you know between cranial and caudal end?

A

Connecting stalk on caudal side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does the primitive streak form?

A

¨Some of the hypoblast cells near the future mouth proliferate and form anterior visceral endoderm (forms the buccopharyngeal membrane)

¨Soon after formation of anterior visceral endoderm epiblast cells near the tail end proliferate and form primitive streak

Cephalic end of primitive streak:

primitive node: slightly elevated surrounding a small pit: primitive pit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Explain Gastrulation

A

¨Epiblast cells migrate towards primitive streak, detach and slip beneath it

¨Some of the slipped epiblast cells displace hypoblast and form endoderm, others come to lie between epiblast and endoderm to form mesoderm, remaining epiblast cells form the ectoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

True or False: During gastrulation all germ layers develop from hypoblast

A

False, epiblast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

True or False: At gastrulation, primitive endoderm is replaced by definitive or embryonic endoderm then mesoderm is formed

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Gastrulation Summary

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Intraembryonic mesoderm migrates all over the embryo in between ectoderm and endoderm except at ________ membrane and _______.

A

buccopharyngeal and cloacal (anal) membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the major signaling centers during gastrulation (understand the structures and mesoderm)

A

8.5.6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How is the neural plate formed?

A

8.5.6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How is left-right asymmetry established during gastrulation?

A

FGF 8 is synthesized by the node and the primitive streak

¨FGF 8 induces expression of Nodal

¨Nodal is restricted to the left side by accumulation of serotonin (5 – HT)

¨SHH and LEFTY 1 prevent nodal expression crossing over to the right side

¨Nodal upregulates LEFTY 2 and PITX 2:

¤PITX2 is the master gene for left sidedness

¤Left sided organs express PITX2 on their left side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is situs inversus?

A

8.5.6

26
Q

What happens if there’s not enough gastrulation?

A

Caudal Agenesis (sirenomelia)

27
Q

What happens when there is too much gastrulation?

A

Sacrococcygeal teratoma

28
Q

What are the key features of sirenomelia?

A

hypoplasia and fusion of lower limbs, vertebral anomalies, renal agenesis, imperforate anus, and genital organ anomalies

29
Q

_______ clusters of pluripotent cells proliferate and form tumors in the region

A

Sacrococcygeal teratoma

Teratomas can also arise from primordial germ cells that fail to migrate to the gonadal ridge

30
Q

High doses of ______l during the third week of gestation kills cells in the anterior midline of the germ disc and produce a deficiency of the midline in craniofacial features resulting in _______

A

alcohol

holoprosencephaly

31
Q

_____ is fused eyes

_____ is a single nasal opening formed by fusion of lateral nasal processes

A

Synophthalmia

Proboscis

32
Q

The primitive node secretes substances e.g. noggin, chordin, and follistatin that allow a region of the ectoderm to develop into ______.

A

nerve tissue

33
Q

Explain neurulation: folding of the neural plate

8.5.6

A

¨Neural plate –> neural groove –> eural folds —> neural tube

¨As neural folds close, neural crest delaminates and migrates away

¨Closure happens first in middle of the tube and then zips rostrally and causally

Separates itself from the surface ectoderm

34
Q

Explain neurulation: folding and closure of the neural plate

A

Folding and closure of the neural tube occurs first in the cervical region

The neural tube then “zips” up toward the head and toward the tail, leaving two openings which are the anterior and posterior neuropores

The anterior neuropore closes around day 25

The posterior neuropore closes around day 28

35
Q

Neural tube defects:

______ failure of neural tube closure

______ failure of the anterior neuropore closure

______ failure of posterior neuropore closure and/or vertebral development

8.5.6

A

Rachischisis (image)

Anencephaly

Spina bifida

NTDs have many genetic and environmental causes, but the strongest correlation is folic acid deficiency

36
Q

Failure of neuropores to close can cause neural tube defects (image)
anterior neuropore: anencephaly
posterior neuropore: spina bifida

A

8.5.6

37
Q

Where is spina bifida most common?

A

lumbosacral region

Causes defects in spinal cord and bones of the spine

38
Q

What is the 4th germ layer and how is it formed?

A

At the time of neurulation, cells at the lateral most edge of the neural plate are induced to form neural crest

The neural crest cells transform from epithelial cells into migratory mesenchymal cells that contribute to forming MANY tissues in the body

Neural crest cells are pluripotential

39
Q

What are neural crest derivatives?

A

Dorsal root ganglia

Autonomic ganglia

Adrenal medulla

Schwann cells

Pia-arachnoid sheath

Skin melanocytes

Thyroid parafollicular cells

Craniofacial skeleton

Teeth odontoblasts

Aorticopulmonary septum (spiral septum of heart)

40
Q

What are the 4 types of mesoderm formed from the primative node?

A

¨Axial mesoderm: passes through the node and migrates along the midline:

forms the notochord

¨Paraxial mesoderm: passes just caudal to the node and migrates slightly laterally:

Forms vertebral bones and associated cartilage, skeletal muscle, and dermis of the back

¨Intermediate mesoderm: Between paraxial and lateral plate mesoderm:

Forms the gonads, kidneys and the duct system of the male reproductive system

Lateral plate mesoderm: passes more caudal and migrates more laterally:

forms limb bones, circulatory system and body cavity linings

41
Q

Subdivisions of the 4 mesoderm

A

Axial mesoderm/Chorda mesoderm

¤notochord

Paraxial mesoderm

¤head mesenchyme

¤somites

sclerotome

myotome

dermatome

Intermediate mesoderm

¤urogenital organs

Lateral plate mesoderm

¤splanchnic (viscera)

¤somatic (body wall)

¤extraembryonic

42
Q

Summary of Mesoderm

A
43
Q

What happens in the paraxial mesoderm?

A

¨Undergoes segmentation:

Forms somitomeres

First appear in cephalic region and formation proceeds caudally

¨From occipital region

caudally somitomeres organize into somites

¨F_irst somite arises on the 20th day_

44
Q

True or False: New somites appear in craniocaudal sequence approximately 3 pairs per day until, at the end of 5th week, 42- 44 pairs are present

A

true

8.5.6

45
Q

What are the correct somite numbers?

A

Upper 4 - occipital somites (supplied by XII cranial nerve)

8 cervical

2 thoracic

5 lumbar

5 sacral

8-10 coccygeal

46
Q

Where does somitogenesis begin?

A

Somitogenesis begins w/ 8th pair of somitomeres

47
Q

How does the separation of somites work?

A

FGF signaling from the node drives proliferation; Retinoic acid from adjacent mesoderm drives differentiation. Because the node is caudal to the forming somites, there is a head-to-tail gradient of differentiation

Proliferating cells express a ligand (called ephrin B1). As cells differentiate, they begin to express an INCOMPATIBLE receptor (called eph A) that causes the differentiating cells to repel the proliferating cells, thus pinching off and forming a new somite

48
Q

How do epithelial somites then transform back into mesenchyme?

A

¨Signaling from ectoderm induces dermomyotome

¨Signaling from notochord and neural tube induces sclerotome

49
Q

How does dermomyotome form dermis and muscle?

A

¨Dorsomedial portion of dermomyotome influenced by notochord becomes muscle that cannot migrate very far (epaxial muscles of the back)

¨Ventrolateral portion of dermomyotome exposed to high levels of BMP from lateral plate mesoderm, becomes migratory muscle (goes into limbs also “hypaxial” muscles of the lateral and ventral body wall, e.g. “latissimus” and “abdominal muscles”

50
Q

How many types of sclerotome are there and what do they develop into?

A

Dorsal sclerotome:

¤Dorsal arch and spinous processes of vertebrae*

Medial sclerotome:

¤Meninges*

Central sclerotome:

¤Pedicles & transverse processes of vertebrae, proximal portions of ribs

Ventral sclerotome:

¤Vertebral bodies and annulus fibrosus of intervertebral disks

Lateral sclerotome:

¤Distal portions of ribs

51
Q

summary of somite derivatives

A

¨Somite (Paraxial mesoderm) forms:

¤Sclerotome

¤Dermomyotome

Sclerotome forms:

meninges, vertebrae and ribs

Dermomyotome forms:

Dermis of the back of the body (from dermatome)

Muscles (from myotome)

52
Q

Intermediate mesoderm develops into the ______

A

urogenital system

8.5.6

53
Q

Lateral plate mesoderm divides into ______ and ______mesoderm

A

somatic and splanchnic

Somatic mesoderm:

Lines body wall (somatic mesoderm + ectoderm = somatopleure)

Splanchnic mesoderm:

Covers endoderm (splanchnic mesoderm + endoderm = splanchnopleure)

8.5.6

54
Q

Somatic (aka parietal) mesoderm stays with epidermis

Splanchnic (aka visceral) mesoderm stays with endoderm

A
55
Q

Blood and blood vessels develop from extraembryonic and lateral plate mesoderm

A

¨Vasculogenesis: blood vessels arise from “hemangioblasts” that develop into blood cells AND vascular tubes

¨Angiogenesis: growth of new blood vessels from existing ones

¨Vessels from extraembryonic mesoderm go out to placenta and eventually hook up with blood vessels (and the heart) in the embryo that arise from lateral plate mesoderm to establish circulation.

¨2 major phases of hematopoiesis:

¤Embryonic (weeks 1-4) : blood cells arise from yolk sac mesoderm

Definitive (week 4-term): blood cells arise from lateral plate mesoderm in the AGM (aorta-gonad-mesonephros region) that go on to seed the spleen, liver, and then bone marrow with hematopoietic stem cells

56
Q

Folding of embryo

A

§Occurs

§Cephalocaudally

§Laterally

57
Q

How does lateral folding work?

A

¨Right and left somatic layer of lateral plate mesoderm fuse together ventrally and form rounded body form

¨Yolk sac gets incorporated into body of embryo- primitive gut tube

¨Communication between yolk sac and gut tube - Vitelline duct

58
Q

What are the simaltaneuous events that happen during the closure of the body wall

A

Purse string-like

closure of the body

wall

Growth of the

amnion

Regression of yolk

sac

59
Q

What happens if the body wall does not close properly?

A

Ectopia cordis:
failure of the thoracic body wall to close

60
Q

_____ is the failure of the abdominal body wall to close

______ is failure of the pelvic body wall to close

______ is failure of most of pelvic body wall to close

A

Gastroschisis

Bladder Exstrophy

Cloacal Exstrophy

61
Q

Summary of Third Week

A

¨Primitive streak

¨Gastrulation à ectoderm, intraembryonic mesoderm and endoderm

¨Notochord formation

¨Neural tube and neural crest formation

¨Paraxial mesoderm à somites

¨Intermediate mesoderm

¨Lateral plate mesoderm cavitation and intraembryonic coelom formation

¨Angiogenesis and primitive heart tube formation

¨Secondary villi à tertiary villi à placental circulation begins

62
Q
A

HBSF Block 1 (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions