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Microanatomy > Gametogenesis, Fertilization, Cleavage and Gastrulation (Germ layers) > Flashcards

Gametogenesis, Fertilization, Cleavage and Gastrulation (Germ layers) Flashcards

(51 cards)

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1
Q

Spermatogenesis (metamorphosis)

A

Spermatogonium (2N), 1
——– S phase (mitosis/ differentiation) ——-
Primary spermatocyte (2N, # of chromos decrease, diploid, 16), 1
——-Meiosis 1———
Secondary spermatocytes (1N, haploid, no DNA duplication, 32), 2
——- Meiosis 2———–
Spermatids (1N, haploid, don’t divide, 64), 4
———- Metamophosis ———
Spermatozoa (1N, flagellum), 4

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2
Q

When is mitosis completed for females?

A

In fetal state, before birth
At birth all eggs are primary oocytes

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3
Q

Oogenesis

A

Oogonium
——– S phase (mitosis/ differentiation) ——-
Primary Oocyte (diplotene, 2N)
——-Meiosis 1———
Secondary Oocyte and First polar body (1N)
——- Meiosis 2———–
Ootid and second polar bodies (1N)
———- differentiation ———
Ovum

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4
Q

What will the primary oocytes undergo?

A

Atresia
360 will ovulate out of the 100,000 after puberty

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5
Q

When is meiosis 1 arrested in females?

A

During primary oocyte at diplotene stage

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6
Q

When is meiosis 1 completed in females?

A

Just before ovulation (all mammals) or after ovulation in the ampulla without sperm (mare and dogs)

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7
Q

When is Meiosis II completed?

A

After sperm penetration at secondary oocyte and polar body

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8
Q

What are the ovulated eggs?

A

Female dogs and mares: primary oocyte
All other species: secondary oocyte

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9
Q

Steps prior to fertilization in females

A
  1. Capacitation of sperm
  2. Binding of sperm with zona pellucida
  3. Acrosome reaction
  4. Penetration of zona pellucida
  5. Sperm-egg cell membrane fusion
  6. Cortical reaction
  7. Completion of Meiosis II (2nd polar body forms)
  8. Pronuclei formation
  9. Union of male and female pronuclei
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10
Q

Capacitation

A

Removal of certain sperm membrane proteins

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11
Q

Acrosome reaction

A

Rupture of outer acrosomal membrane
Hydrolytic enzymes released
Motility increases resulting in zona penetration

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12
Q

Cortical reaction

A

Release of glycoprotein granules from cytoplasm of egg
Hardens the zona pellucida and alters oocyte membrane to prevent polyspermy

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13
Q

Pronuclei formation

A

Sperm nucleus is heterochromatic (must condense)
Ovum chromos must coil

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14
Q

Union of pronuclei

A

Fertilization
Results in restoration of 2N chromo number
Forms zygote

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15
Q

What are the results of fertilization?

A

Completion of Meiosis II
Restoration of diploid chromo number
Determination of genetic sex
Initiation of cleavage

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16
Q

Cleavage

A

Division of zygote into many cells without an increase in mass cytoplasm

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17
Q

Blastomeres

A

Cells that lie within the confines of zona pellucida

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18
Q

Morula

A

A clumped group of 8-16 cells formed by cleavage
Latin name for “small mulberry”

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19
Q

Most embryos reach the ______ at the _________ stage.

A
  1. Uterus
  2. Morula
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20
Q

When is morula stage (uterus) reached for most species?

A

4-5 days

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21
Q

What happens to blastomeres after stage 8?

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A

They lose their universal potential
Each blastomere can no longer become an embryo

22
Q

What is the second stage of the blastomere?

23
Q

Blastocoel

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A

Cavity formed when fluid-filled spaces coalesce among blastomeres

24
Q

Trophoblast

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A

Formed when blastomeres surround the blastocoel
Future amnion and chorion

25
Inner cell mass (embyro proper)
When some blastomeres form a mass at one end of the blastcoel
26
How long does the blastula stage last?
5-9 days after ovulation
27
What are the stages of the blastomere?
1. Blastomere 2. Morula 3. Blastula 4. Hatching (degeneration of zona pellucida) 5. Gastrulation (germ layers developed)
28
Hatching
Degeneration of the zona pellucida Degenerates one day after completion of blastula
29
Which species are exceptions to hatching?
Horses Pigs and ruminants
30
What happens to the zona pelucida in horses?
It's replaced by glycoprotein capsule (neo-zona) Remains until 21 days of gestation
31
What happens after hatching in pigs and ruminants?
Trophoblast undergoes a rapid elongation Up to 1 meter long in pigs and 35 cm in ruminant
32
For pigs, when is elongation completed?
9-16 days of gestation
33
For ruminants, when is elongation completed?
12-14 days of gestation
34
Formation of Primitive Streak (P.S.)
Thickening of caudal end of epiblast cells due to proliferation Formation of 2 ridges and a central groove along the diameter of a streak
35
What is the significance of PS?
First step in the formation of mesoderm Establishes cranial and caudal ends of the embryo
36
Primitive node (Hensen's node)
Formed by the cranial most end of the primitive streak
37
What is the notochord remnant in adults?
Nucleus pulposus
38
How is the mesoderm split?
Paraxial (closer to notochord) Intermediate Lateral (develops coelom and divided into somatic and splanchnic)
39
Differentiation of somite
Paraxial/ mesoderm differentiates on each side of notochord into somite Somite formation begins cranially and extends caudally
40
What is each vertebral somite represented by?
One pair of somite, each pair constant for each species Number of pairs can be related to age of embryo
41
What are the parts of a somite?
1. Sclerotome: vetebrae (axial skeleton) 2. Myotome: skeletal musculature of body except head region 3. Dermatome: dermis underlying CT of skin
42
What does ectoderm form?
Epidermis of the skin Epithelium of the oral and nasal cavities Nervous system and sense organs
43
What does mesoderm form?
Muscle and CT Including bone, components of circulatory, urinary and genital systems
44
What does endoderm form?
Mucosal epithelium and glands of respiratory and digestive systems
45
Aplasia/ hyplasia
Dwarfism
46
Cranio-facial defects
Abnormal neural crest migration
47
Amelia
Absense of extremities
48
Meromelia
Partial absence of extremity
49
Micromelia
Short extremity
50
Polydactyly
Extra digits
51
Syndactyly
Fused digits

Microanatomy (18 decks)

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