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Histology > Embryology 1 > Flashcards

Embryology 1 Flashcards

1
Q

What is the word used to explain pre-natal development?

A

embryogenesis

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2
Q

What processes does embryogenesis include?

A
  • organogenesis
  • proliferation
  • specialization
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3
Q

What is organogenesis?

A

the formation of body structures & organs

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4
Q

What is proliferation?

A

cell division

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5
Q

What is specialization?

A

cell differentiation

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6
Q

What does embyogenesis produce?

A

The great variety of cell types and extracellular products found in the body.

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7
Q

What is the ‘time’ in which ‘embryology’ occurs?

A

fetus –> giving birth

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8
Q

What is the first cell of the organism? What marks the beginning of the prenatal period?

A
  • female/male sex cell
  • oocyte/spermatozoa cell
  • union of these two cells marks the beginning of the prenatal period
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9
Q

What is the first stage of embryogenesis?

A

pre-embryonic stage: period of proliferation of specialization (differentiation) of the zygote.

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10
Q

What is the second stage of embryogenesis?

A

embryonic period:
- organogenesis
- formation of body structures and organs
- the time from fertilization to the earliest (primordial) stages of organ development
- 30 days- dog, cat, sheep, pig;
60 days- horse, cattle, human.

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11
Q

What is the third and final stage of embryogenesis?

A

fetus period:
- maturation of tissues and organs
- rapid body growth
- the time between the embryonic period and parturition (the end of gestation)

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12
Q

What is the name of the mature sperm cell?

A

spermatozoa

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13
Q

Explain the structure of the spermatozoa.

A
  • flattened head
    covered by the acrosomal cap (+ hydrolytic enzymes)
  • axonemal complex in the sperm tail (+ mitochondria)
  • short neck (+ centrioles +origin of the coarse fibers)
  • middle piece (+mitochondria)
  • principal piece (+fibrous sheath)
  • end piece (+axonemal complex)
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14
Q

What does the acrosomal cap include? What is its function?

A
  • hydrolytic enzymes
  • penetration of the
    ovum
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15
Q

What is the sperm tail axonemal complex helically wrapped by?

A

mitochondria

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16
Q

What does the sperm short neck include?

A
  • centrioles
  • origin of the coarse fibers
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17
Q

What does the middle piece of spermatozoa include? What is its function?

A

Mitochondria:
- helically wrapped (around the coarse fibers and the axonemal complex).
- provide the energy for movement of the tail
- responsible for the motility of the sperm.

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18
Q

What does the principal piece of spermatozoa contain?

A

fibrous sheath:
- external to the
coarse fibers and the axonemal complex.

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19
Q

What does the end piece of spermatozoa contain?

A

axonemal complex

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20
Q

What are the 4 principal pieces of spermatozoa?

A

1) head (+acrosome, nucleus, connecting piece)
2) midpiece (+mitochondrial sheath)
3) principal piece
4) end piece

2+3+4=sperm tail

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21
Q

What is the correletion between the neck and midpiece of the spermatozoa?

A
  • neck is a part of the midpiece
  • midpiece is the first part of the tail (proximal to the head)
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22
Q

What is the neck of a sperm?

A

The binding site of the spermatozoa head and tail.
- very short

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23
Q

What are some principal features of the tail?

A
  • densely packed mitochondria
  • central pair of microtubules (core)
  • outer doublets
  • outer dense fibers
  • fibrous sheath
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24
Q

What is the function of the cell cytoskeleton?

A
  • prevents cell from collapsing
  • maintains cell shape and structure
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25
Q

How does the cytoskeleton of spermatozoa compare to that of other cells?

A

In spermatozoa all microtubules are unidirectional, while in otehr cells, the cytoskeleton forms a 3D structure of network fibers going multiple directions.

reason for difference in shape (spermatozoa vs other cells)

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26
Q

What can be seen in a cross section of a spermatozoa cell seen under an electron microscope?

A
  • axoneme
  • doublets of the axoneme
  • central pair
  • plasma membrane
  • mitochondria
  • outer dense fiber
  • longitudinal column of the FS
  • circumferential ribs of the FS
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27
Q

Can spermatozoa cells move right after being produced in the testes?

A

no!! they must go to the epidydimis to undergo a maturation process.

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28
Q

Where do spermatozoa go once they are produced? What happens?

A

production (testes) –> epidydimis

  • aquire motility
  • undergo further maturation
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29
Q

What initiates sperm cell motility during cell transit through the epididymis?

A

changes in chemical components:
- intracellular levels of cyclic adenosine monophosphate (cAMP),
- intracellular levels of calcium ions (Ca2+),
- intracellular pH.

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30
Q

Where can oocytes be found?

A

in ovarian follicles

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31
Q

What is the ovarian follicle?

A

Structure composed of an oocyte surrounded by specialised epithelial cells.

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32
Q

What is the composition of the primordial follicle?

A
  • oocyte
  • follicular cells
  • stromal cells (simple squamous epithelium)
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33
Q

What is the composition of the unilaminar primary follicle?

A
  • oocyte
  • basal lamina (simple cuboidal epithelium)
  • zona pellucida forming
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34
Q

What is the composition of the multilaminar primary follicle?

A
  • oocyte
  • zona pellucida
  • granulosa cells (stratified cuboidal epithelium)
  • theca interna
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35
Q

What is the composition of the antral (secondary) follicle?

A
  • oocyte
  • granulosa cells
  • theca interna
  • theca externa
  • antrums (multiple small gaps)
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36
Q

What is the composition of the mature (graafian) follicle?

A
  • oocyte
  • corona radiata
  • cumulus oophorus
  • granulosa cells
  • theca interna
  • theca externa
  • antrum (very large space filed with liquid)
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37
Q

What happens during ovulation?

A

The structure of the mature (graafian) follicle ruptures (fertilation can occur).

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38
Q

What is fertilization?

A

The fusion of gametes to initiate the development of a new individual organism.
- oocyte + sperm cell
- generates full set of chromosomes (zygote=diploid; sex cells=haploid)
- genes mix together forming a new individual
- zygote is activated initiating zygote development

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39
Q

What are the three important processes occuring during fertilization?

A

1) capacitation
2) acrosome reaction
3) cortical reaction

40
Q

What is capacitation?

A
  • preparation of spermatozoa in the female genital tract.
  • female environment modifies the outer surface of the acrosome:
    removes glycoproteins and
    proteins. (final maturation step of the spermatozoa)
  • spermatozoa become hyperactive and make their way
    through the cervix, uterus and uterine tube to find the ovum
41
Q

What is the acrosome reaction?

A

1) spermatozoa must break the oocyte corona radiata

2) spermatozoon encounters the zona pellucida surrounding the oocyte plasma membrane and insulating it from the
external environment.

  • The spermatozoon binds to the zona pellucida and is triggered to begin the acrosome reaction:
  • acrosomal cap breaks down
  • releases enzymes that dissolve the zona pellucida (locally) allowing the spermatozoon to enter the oocyte
42
Q

What is teh cortical reaction?

A
  • through the zona pellucida: membranes of the egg and
    sperm fuse,
  • contents of the sperm are now within the egg.
  • egg releases cortical granules (containing enzymes),
  • binding proteins of the entire zona pellucida become altered,
  • prevention of further sperm binding.
43
Q

What is the fertilization by multiple sperm called?

A

polyspermy/dispermy

44
Q

What is the function of the zona pellucida, acrosome and cortical reaction?

A

prevents polyspermy/dispermy

45
Q

Why is polyspermy bad?

A

hundreds of sperm reach the egg at the same time –> dispermy createz an embryo with three haploid sets of chromosomes
(triploidy) that would be extremely unlikely to survive.

46
Q

What is another way of calling “sperm activation”?

A

capacitation

47
Q

Does the spermatozoa enter the ooxyte?

A

no! the cell membranes fuse, and only the genetic material is transferred.

48
Q

Once fertilized, how can teh cell be called?

A

a zygote = pleuripotent cell

49
Q

What is a pleuripotent cell?

A

a cell which is capable of developing into a new individual

50
Q

What does fertilization begin and end with?

A

begins: gamete fusion (zygote formation)
ends: initiation of zygote cell division (the start of
cleavage)

51
Q

Through what process does the zygote divide into many different cells?

A

mitosis

52
Q

What is “cleavage”?

A

the initial series of mitotic divisions by which the large
zygote is fractionated into numerous “normal size” cells.

53
Q

What is each daughter cell of the cleavage process referred to as?

A

blastomere

54
Q

Explain the cleavage process.

A
  • beginning: zygote
  • compaction to a morula stage
  • termination: start of the blastocyst (blastula) stage
  • first eight blastomeres = undifferentiated (have
    identical potential in mammals);
  • other blastomeres differentiate into inner & outer cells (different missions).
55
Q

What does each blastomere include?

A

identical composition:
- full paternal and maternal chromosomes

56
Q

When does cleavage begin? (turning of zygote into blastomeres)

A
  • zygote is still in the uterine tube
  • not in the uterus!!
57
Q

All cells of the mitotic divisions are equal in what? What does this cause the name of the cleavage to be?

A
  • size
  • composition

= total/equal cleavage

58
Q

How does the total mass of the living substance change as the mitotic divisions continue?

A

no change!
- more cells of smaller size
- total mass does not increase!

59
Q

What happens a few days after fertilization?

A
  • the cluster of blastomeres passes through the uterine tube into the uterus
  • cluster of cells= morula
60
Q

What is a morula? What is it composed of? What surrounds it? Are the cells different? How?

A
  • a solid ball of blastomeres (16-64)
  • within a zona pellucida
  • blastomeres become compacted;
  • inside blastomeres: differentiate + develop the capacity to secrete fluid
  • outer blastomeres: attened and form tight junctions (reducing
    fluid permeability);
61
Q

What is the function of the tight junctions created by outer blastomeres of teh macula?

A

reduce fluid permeability

62
Q

What are the outer blastocytes destined to become? What does this later contribute to?

A

trophoblasts:
- form the chorion & amnion (fetal membranes) of the conceptus
- form the placenta

63
Q

What happens as more blastocytes develop? What does it later turn into?

A

fluid center is formed –> common blastocoele cavity

64
Q

State the different parts of the blastocyst. Other names?

A
  • inner cell mass (embryoblast)
  • trophoctoderm (trophoblast)
  • blastoceole (cavity)
65
Q

What does a large number of blastomeres form?

A

blastocyst (blastula)

66
Q

What is a blastocyst? What is it composed of? What does it form? How does it look?

A
  • large number of blastomeres
  • form a hollow, fluid-filled, spherical or cylindrical structure
  • embryoblast: inner cell mass (collection of cells)
  • trophoblast: surface cells
  • blastocoele: the cavity
67
Q

What eventually happens to the blastocyst?

A

attaches to / implants within the uterine wall

68
Q

Which part of the blastocyst will develop into an embryo?

A

only the inner cell mass = embryoblast

69
Q

What is implantation? Why does it occur? When does it occur?

A
  • stage of pregnancy at
    which the embryo
    adheres     to the uterus wall
  • allows embryo to recieve oxygen and nutrients to grow
  • 6-10 days after fertilization
  • note: blastocyst secretes enzymes which slightly atler the uterine lining allowing for bettwe attachment/embedding
70
Q

What is placentation?

A
  • the creation of the placenta by the fusion of the uterine wall with the blastocyst
71
Q

What is special about the uterine lining?

A
  • it is liable!
  • blastocyst can insert itself in many different uterus wall locations (no predetermined attachment point)
72
Q

How does the uterus lining prepare itself for blastocyst landing?

A
  • ovarian hormones
  • uterine glands produce secretions which nourishes the embryo early stages
73
Q

What is aptopic pregnancy? When does it occur? How does it end?

A
  • blastocyst doesn’t reach the uterine lining
  • implants itself elsewhere (uterine tube)
  • fatal for both the mother and embryo
74
Q

What is the placenta? Which membranes? What happens there?

A

region of apposition between:
- *uterine lining *
- fetal membranes

metabolites are exchanged for sustaining pregnancy.

75
Q

What does the chorion form?

A

the surface fetal membrane

76
Q

What are the different apposition areas (placental types)?

A

carnivore: zonary

ruminants: cotyledonary

pig: diffuse
horse: diffuse

primates: discoid
rodents: discoid

77
Q

What type of organ does the placenta qualify as?

A

a temporal organ

78
Q

What are the two components of the placenta? Different names? What do they develop from?

A

1) fetal placenta:
- chorion frondosum
- develops from the same blastocyst that forms the fetus,

2) maternal placenta:
- decidua basalis
- develops from the maternal uterine tissue

79
Q

How many fetal membranes develop in a conceptus?

A

4

80
Q

Does the chorion cover the whole placenta?

A

no! eg. zonary chorion, only center

81
Q

What is the function of the “watery pool”?

A

amnion:
- absorbs shock
- applies pressure
- permits the feature to chaneg its posture

81
Q

How is the amnion formed? What does it enclose?

A
  • formed by folds of the chorion (in domestic mammals)
  • encloses the embryo within a fluid-filled amnionic cavity
  • transparent, non vascular membrane
  • gradually fills the embryonic sac (later fuses with it)
  • filled with clear fluid (watery pool)
82
Q

What is the allantois? What does it provide?

A
  • a fetal membrane
  • highly vascularized
  • provides the functional vessels of the placenta (via umbillical vessels)
  • the outer surface of allantois binds to the:
  • inner surface of chorion
  • outer surface of amnion
83
Q

What is the yolk sac?

A

membranous sac attached to an embryo

84
Q

What is the importance of the yolk sac?

A
  • early embryonic blood supply
  • early embryonic nutrition
85
Q

How is the yolk sac formed?

A
  • cells split of from the inner cell mass of the blastocyst
86
Q

What species have large yolk sacs?

A
  • amphibians
  • birds

(nearly unexistant in mammals)

87
Q

What are monozygotic twins?

A

identical (same genetic
composition) twins

88
Q

How can monozygotic twins form?

A

1) separation of early blastomeres (up to
the 8-cell stage)
- (each of the separate blastomeres develops into an independent
conceptus)

2) separation of inner blastomeres within a
single morula
- (each of the separate
blastomeres develops into an independent embryo and both embryos share a common
placenta)
- (less common)

89
Q

How do conjoined twins form?

A

due to the seperation in later embryonic development

90
Q

What is the umbillical chord?

A
  • a conduit between the developing embryo/fetus and the
    placenta
  • cylindrical chord
  • has 2 arteries, 1/2 veins, and wharton’s jelly
91
Q

During prenatal development, what is the umbillical chord physiologically and genetically part of?

A

the fetus

92
Q

What does the umbillical chord contain?

A
  • two umbilical arteries
  • one/two umbilical veins
  • buried within Wharton’s jelly
93
Q

What supplies the fetus with oxygenated, nutrient-rich blood
from the placenta?

A

umbilical vein

94
Q

What is the function of the umbilical artery?

A

fetal heart pumps blood back to the placenta:
- low oxygen
- nutrient-depleted

95
Q

What is the function of the umbilical vein?

A

supplies the fetus with blood:
- oxygenated
- nutrient-rich

96
Q

What is Wharton’s jelly?

A
  • embryonic connective tissue
  • similar to mesenchyme

Histology (20 decks)

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