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Flashcards in Embryology Deck (69):
1

Gametogenesis

Formation of male & female gametes

2

Parts of spermatozoa

- Head piece = primarily comprised of nucleus w/ cap of protein (acrosome)

- middle piece = houses mitochondria

- tail = mostly microtubules; motility

3

Secondary oocyte

- cell that is ovulated
- surrounded by zona pellucida & corona radiata

4

Zone Pellucida

Protein coat that surrounds secondary oocyte

5

Corona radiata

- Surrounds zona pellucida
- network of follicular cells

6

what are Primordial germ cells (PGCs)

- precursors to the development of the gametes in both males & females

7

Describe the development of PGCs

- Week 2: develop from Epiblast cell line

- Week 4: migrate to yolk sac

- Weeks 4-6 migrate from yolk sac --> developing gonads (ovary & testis); undergo rapid mitosis during migration

- Once they've reached gonads, begin gametogenesis by entering meiosis

8

What happens if PGCs fail to migrate properly

no gonad will develop on that side

9

Describe Meiosis

Meiosis I:
- synapsis
- chromosome crossovers
- disjunction & cell division

Meiosis II
- no synapsis or crossover
- disjunction & cell division (with centromere splitting)

10

What are the 2 types of spermatogonia & how do they differ?

Type A:
- remain in the seminiferous tubules for lifetime
- continually go through mitosis
- stem cells

Type B:
- go through meiosis I & II
- form haploid spermatozoa
- waves of meiosis & spermatogenesis occur for life

11

Describe the path for sperm production

PCG's --> future testies --> puberty --> type A spermatogonia --> type B spermatogonia --> Meiosis I (primary spermatocyte) --> Meiosis II (secondary spermatocyte) --> spermatids --> spermiogenesis --> spermatozoa

12

what does -gonia mean

cell that is pre-meiotic

13

what does 1° mean

cell that is in meiosis I

14

what does 2° mean

cell that is in meiosis II

15

In a male, a single round of meiosis produces ____ daughter cell(s) that are ____ in number

In a female, a single round of meiosis produces ___ daughter cell(s) that are ___ in number

4; haploid


1; haploid

16

Describe the path for Oogenesis

PCGs migrate from yolk --> future ovary --> immediately begin to differentiate into oogonia --> rapid mitotic division --> meiosis I (5th month; primary oocytes) --> prophase of meiosis I & wait --> puberty --> continue meiosis I --> secondary oocyte/meiosis II within griffin follicle --> arrested in metaphase of meiosis II --> mid cycle of ovulation --> fertilization --> complete meiosis II --> mature ovum

if its not fertilized, it gets discarded

17

Steps in Fertilization

1. capacitation
2. penetration of corona radiata
3. acromosome reaction (penetration of zone pellucida)
4. fusion of male & female membranes
5. cortisol (zonal) reaction
6. formation of male pronucleus
7. completion of second meiotic division of oocyte & formation of female pronucleus
8. fusion of male & female pronucleus

18

where does fertilization take place

ampulla - the distal end of the uterine tube

19

the corona radiate and zone pellucida are derived from the ____

griffin follicle

20

Explain the capacitation reaction

- takes 7-8 hours
occurs primarily while sperm are traveling thru uterine tube
- results in rearrangement of proteins on the acromosome cap
- render it capable of penetrating the corona radiate

21

Explain the acrosome reaction

- takes place when sperm head comes into contact with zone pellucida
- pores open on head & release proteolytic enzymes that bore thru zone pellucida
- allows sperm head to enter secondary oocyte

22

explain the cortical (or zonal) reaction

- triggers the secondary oocyte impermeable to any other spermatozoa to prevent polyspermia

23

the ____ houses the primary oocyte in its arrested state from the 5th month of development

primordial follicle

24

Primordial follicle becomes the _____ which becomes the _______ which is crucial in the production of estrogen

primary follicle --> secondary follicle

25

The graffian follicle develops from the _____ at around day 14

secondary follicle

26

the secondary oocyte is ovulated FROM the ______ & brings with it the _____ & _____

griffin follicle; zona pellucida & corona radiata

27

the zona pellucida & corona radiata are derived from

the graffian follicle

28

the secondary oocyte is ovulated INTO the

peritoneal cavity

29

cleavage consists of

a series of mitotic cell divisions

30

Why does the zona pellucida remain intact throughout cleavage?

prevents the ball of cells from increasing mass & serves as a barrier to prevent the developing embryo from adhering to the wall of the uterine tube

31

When does the zona pellucida degrade?

Day 5 during the morula stage

32

At the blastocyst stage, some of the cells get pushed to one pole, forming a homogeneous mass of cells called the ______ & other cells form a shell-like perimeter called the ____

embryoblast; trophoblast

33

the ____ forms the placenta that supports the embryo

trophoblast

34

in order for implantation to take place, the trophoblast cells undergo differentiation into ____ & _____

cytotrophoblasts & syncytiotrophblasts

35

_____ is an abnormality of ciliary movement & can increase the risk of ectopic implantation

kartagener syndrome

36

____ is the most common site of ectopic implantation

ampulla

37

the epiblast and hypoblast are derived from the

embryoblast

38

the ___ reorganizes into a bilaminar disc comprised of two distinct cell layers: ___ & ___

embryoblast

epiblast cells (dorsal surface) & hypoblast cells (ventral surface)

39

the ____ lays down the extraembryonic mesoderm

hypoblast

40

the _____ are the cells that release enzymes & serve as the invading cells for implantation

syncytiotrophoblasts

41

the ___ is formed as a cleft in the epiblast cell layer that becomes filled with fluid secreted by the epiblast cells called ______

amnion; amniotic fluid

42

epiblast cells forming the roof of the amnion are called ____ & produce amniotic fluid

amnioblasts

43

in early week 2 the hypoblast cells send out a layer of cells called the ______ which line the inner surface of the trophoblast surrounding the blastocyst cavity

Heuser's membrane

44

once the Heuser's membrane is formed, the old blastocyst cavity is now referred to as the

primary yolk sac

45

levels of amniotic fluid that are too high during gestation

polyhydramnios

46

levels of amniotic fluid that are too low during gestation

oligohydramnios

47

layer between the Heuser's membrane and trophoblast layer

extraembryonic mesoderm

48

the extraembyronic mesoderm layer begins to develop vacuoles within it which will coalesce into a new space called the

chorionic space

49

the position of chorionic cavity divides the extraembryonic membrane into inner and outer layers called the ___ & ___

extraembryonic splanchnic mesoderm (visceral, inner layer)

extraembryonic somatic mesoderm (outer layer)

50

At the end of week 2 the hypoblast cells push the primary yolk sac away from the embryo resulting in the formation of the

definitive yolk sac

51

3 major roles of definitive yolk sac

1. housing of primordial germ cells early in development
2. early hematopoiesis (blood cell development)
3. primitive gut tube

52

what do the uterine glands supply

glycogen

53

what are lacunar networks

large lakes of blood that are the beginnings of a rudimentary placental circulation

54

____ are the future site of fetal circulation; they become the vascular system to the embryo

primary villi

55

hCG is secreted by

syncytiotrophoblast cells

56

the ____ allows for the production of progesterone & estrogen

corpus luteum

57

hCG is released until _____ ensuring that ___ is maintained

the placenta is fully developed, ensuring that endocrine support is maintained

58

thickening at one end of the bilaminar disc

prechordal plate

59

In gastrulation, the epiblast cells of week 2 are transformed into ____ consisting of 3 germ layers

trilaminar disc

60

the _____ is formed along the cranial-caudal axis in the first stage of gastrulation

primitive streak (groove)

61

the cranial end of the disc is demarcated by the presence of the ________

prechordal plate

62

the caudal end of the disc is demarcated by the presence of the

cloacal membrane

63

gastrulation is the migration of ____ through the ____

epiblast cells; primitive streak

64

the cranial end of the primitive streak is called the

primitive node

65

the center point of the primitive node is called the

primitive pit

66

the epiblast that displace the hypoblast will form the

endoderm

67

the epiblast cells that fill the space b/w the hypoblast and epiblast layers form the

mesoderm

68

the epiblast cells that don't migrate through the primitive streak form the

ectoderm

69

the _____ is comprised of endodermal, mesodermal and ectodermal germ cell lines

trilaminar disc