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2. Physiology > Spermatogenesis > Flashcards

Spermatogenesis Flashcards

1
Q

Spermatogenesis

A
  1. Proliferation: stem cells and spermatogonia divide via mitosis
  2. Meiosis 1: Primary spermatocytes (64)
  3. Meiosis 2: Secondary spermatocytes (128)
  4. Differentiation: spermatids (no divison)
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2
Q

Formation of the acrosome

A

An organelle with enzymes (hyluronidase and acrosin) assist sperm penetrate through ZP

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3
Q

Development of flagella and mitochondria

A

Attains motility to deliver males’s genetic info to an oocyte during fertilization

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4
Q

DNA condensation

A

Convert DNA into an inactivate state to prevent damage (histones replaced with protamine)

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5
Q

Caput (head) sperm are _____________

A

Immotile

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6
Q

Caudal (tail) sperm are ____________

A

Motile

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7
Q

Sperm penetrating the oocyte

A
  1. Immediate transport: retrograde loss, phagocytosis, entrance into cervix
  2. Cervix: remove non-motile and abnormal sperm
  3. Uterus: Capacitation (sperm gets fertilizing ability), phagocytosis
  4. Oviduct: Capacitation completed, hyperactive motility
  5. Fertilization: Acrosome reaction, sperm penetrates, pronuclei form
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8
Q

What do epidermal sperm membranes have?

A

Complement of surface proteins and carbs

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9
Q

What happens to epidermal sperm membrane once ejaculated?

A

Surface molecules are coated with seminal plasma proteins

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10
Q

What happens to epidermal sperm membrane once it’s capacitated?

A

In the female repro tract, seminal plasma protein removed exposing portion of the molecules that bind to the ZP
Hyperactive motility

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11
Q

Hyperactive motility

A

Required for sperm to disperse cumulus (follicular cells) that surround the oocyte to penetrate the ZP (move them out the way!!)

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12
Q

Acrosomal reaction

A

Release of acrosomal enzymes to allow sperm to digest through the ZP by plasma membrane fuses with outer acrosomal membrane leading to the creation of pores

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13
Q

What happens after the sperm penetrates the ZP?

A

It reaches the perivitelline space

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14
Q

What happens during membrane fusion?

A

Plasma membrane of the oocyte fuses with the equatorial segment, fertilizing the sperm
Cortical reaction

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15
Q

Cortical reaction

A

Contents of the cortical granules released preventing penetration by other sperm

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16
Q

What happens after membrane fusion?

A

The nuclear membrane disappears and the nucleus of the sperm decondenses

17
Q

What happens when there’s no conceptus

A

Oxytocin receptors increased (milk letdown)
Oxytocin released by luteal cells and binds to receptors causing PGF2a to synthesize and release

18
Q

What happens when there’s conceptus present?

A

Progesterone maintains pregnancy
Early embryo signals about its presence so the OTr receptors don’t develop
CL doesn’t degenerate and secretes progesterone

19
Q

4 steps before embryo can attach to the uterus

A

Development of embryo within confines of ZP
Hatching of the blastocyst from the ZP
Maternal recognition of pregnancy
Formation of extraembryonic membranes (yolk sac, allantois, chorion and amnion)

20
Q

Placenta in cattle and sheep

A

Allantois and chorion fuse and form allantochorion
Allantochorion interacts with endometrium of uterus to generate fetal cotyledons

21
Q

Functions of the placenta

A

Metabolic exchange
Elimination of waste products
Gas-exchange
Thermo-regulation
Endocrine organ during pregnancy

22
Q

How does the placenta serve as an endocrine organ in the Mares

A

Secretes equine chorionic gonadotropin (eCG or PMSG) and maintains CL, forms and maintains the copora lutea (progesterone production)
50-70days of pregnancy

23
Q

How does the placenta serve as an endocrine organ in other animals

A

Maintains progesterone with CL
Estradiol secretion in last part of gestation and induction of parturition
Placenta lactogen secretion (like GH)
Source of hormone relaxin

24
Q

What does progesterone do in early embryonic development?

A

Provides stimulus for increased secretion of endometrial glands
Blocks myometrial contraction

25
Q

When does the placenta take over progest. production

A

Sheep: day 50 of gestation
Cattle: 6th, 7th, 8th month

26
Q

What happens at the time of parturition?

A

Placental progesterone converts to estradiol
Dramatic drop in progest.

27
Q

What enzymes contribute to progest. conversion to etradiol?

A

Hydroxyprogest.
Androstenedione
Hydroxylase
Desmolase
Aromatase

28
Q

3 stages of parturition

A
  1. Myometrial contraction due to drop in P4
  2. Expulsion of fetus–> strong myometrial and abdominal contractions
  3. Expulsion of fetal membrane
29
Q

Wht does fetal stress do?

A

Increase ACTH and cortisol (converts P4 to estradiol and causes luteolysis)

30
Q

What happens when the fetus moves through the birth canal?

A

Elevated pressure on cervix stimulates sensory neurons
Signal sent to paraventricular nucleus –> oxytocin –> myometrium contractions

2. Physiology (15 decks)

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