Spermatogenesis and Oogenesis

Question 1

Spermatogenesis

Answer 1

Process of formation of sperm

• begins at puberty
• rarely totally ceases

Question 2

Where is the site of sperm formation?

Answer 2

Seminiferous tubule of the testicle

Question 3

Events of spermatogenesis

Answer 3

Start with 2n chromosome (spermatogonium) –> mitotic division = primary spermatocyte (2n) –> at end of meiosis 1 = secondary spermatocyte (2 1n chromosomes) –> meiosis 2 = early spermatids (4 n chromosomes) –> differentiation, seroli cells provide nutrients –> sperm cells (spermatozoa)

Question 4

Spermatogenesis progress from the cortex of the semineferous tubule and ends in the _____

Answer 4

Lumen

- where fully formed sperm cells are released

Question 5

Each spermatogonia produces _____

Answer 5

4 sperm cells

- 1:4 ratio

Question 6

Events of oogonium

Answer 6

Begin with primary oocyte (2n) –> meiosis 1 = secondary oocyte and first polar body –> secondary ooctye undergoes meiosis 2 = ootid and second polar body –> ootid differentiates into 1 ovum

Question 7

Females only produce _____ from an oogonium

Answer 7

1 ovum

- do not undergo mitosis!!!

Question 8

Seasonality’s effect on spermatogenesis

Answer 8

Produce sperm throughout the year, but may produce more during the species’ season of breeding
- high vs low production

Question 9

Meiosis 1

Answer 9

2 haploid cells form

• chromosomes are still double
• telophase and cytokinesis with cleavage furrow

Question 10

Meiosis 2

Answer 10

Sister chromatids separated

• 4 haploid daughter cells result
• contains single chromosomes
• prophase 2 - telophase 2

Question 11

Epididymis

Answer 11

Storage of produced sperm

Question 12

Blood flow of the testicle

Answer 12

Enters testicular artery

• artery and venous return are intertwined = pampiniform plexus
• acts to cool the blood entering the testis

Question 13

Testosterone secreted by Leydig cells has a _______ feedback

Answer 13

Negative

Question 14

LH stimulates Leydig cells to secrete ______

Answer 14

Testosterone

Question 15

FSH stimulates Sertoli cells to produce _____

Answer 15

Inhibin

• also converts testosterone to estrogen
• helps with spermiogenesis

Question 16

Males: LH released from AP in a ______ fashion

Answer 16

Pulsatile

• only have a tonic center, no surge
• prevents refractoriness to sustained LH

Question 17

Testosterone secretion is ______ and ______

Answer 17

Short; pulsatile

- elevated testosterone in testis is essential for spermatogenesis

Question 18

Pampiniform plexus helps maintain high levels of ______ in the testis

Answer 18

Testosterone

Question 19

Large spikes of _____ has a negative feedback and ______ LH production

Answer 19

Testosterone; downregulates

Question 20

Is peripheral blood a good indicator of the testicular environment?

Answer 20

No, 500x dilution of testosterone, estrogen, and DHT by systemic circulation

Question 21

What are the 3 biological events involved in spermatogenesis?

Answer 21

• mitosis
• meiosis
• spermiogenesis

Question 22

Mitosis

Answer 22

Proliferation phase which allows for continual supply of germ cells

Question 23

Meiosis

Answer 23

• allows for diploid to haploid
• allows for crossing over
• assures genetic diversity

Question 24

Spermiogenesis

Answer 24

Dramatic morphological changes from spermatids to spermatozoa

Question 25

The proliferation phase of spermatogenesis occurs in the ______ area of the seminiferous tubules

Answer 25

Basal

Question 26

Meiosis and differentiation of spermatogenesis occurs in the ______ area of the seminiferous tubules

Answer 26

Adluminal

Question 27

______ envelop the developing spermatogonia

Answer 27

Seroli cells

Question 28

What process of spermatogenesis is very heat sensitive?

Answer 28

Maturation of spermatogonia into primary spermatocytes | - mitosis

Question 29

Primary spermatocytes undergo _____ and form ______

Answer 29

Meiosis 1; secondary spermatocytes | - haploid!

Question 30

Secondary spermatocytes undergo ____ and become ______

Answer 30

Meiosis 2; spermatids

Question 31

What is one cycle of the seminiferous tubule?

Answer 31

Progression through all stages at one location along a seminiferous tubule - cycle length is unique to each species

Question 32

What are the approx days to complete spermatogenesis for the bull and stallion?

Answer 32

- bull: 61 days | - stallion: 55 days

Question 33

Stages of cycle

Answer 33

Arbirtarily defined cellular associations that transition one to the next at predictable intervals

Question 34

Breakdown of spermatogenesis in the bull

Answer 34

8 stages in the bull - takes 13.5 days to transition thu all 8 stages (or 1 cycle) - complete spermatogenesis takes 4.5 cycles - 4.5 cycles x 13.5 days = 61 days

Question 35

Spermatogenesis must occur _____ cooler than body temperature

Answer 35

3-7 degrees C

Question 36

What structures are involved in temperature control of the testicles?

Answer 36

- scrotal sweating - tunica dartos muscle - cremaster muscle - pampiniform plexus

Question 37

Blood testis barrier

Answer 37

Sertoli cells are joined by tight junctions which effectively create a barrier from the immune system - allows metabolism of developing sperm to occur in a controlled environment - developing sperm are not allowed access to the interstitial space where the immune system will recognize them as foreign

Question 38

Sex determination

Answer 38

One pair of chromosomes determines sex of the animal

Question 39

Females can only contribute an ____

Answer 39

X

Question 40

Males contribute an ____ or a _____

Answer 40

X; Y

Question 41

Sex of the offspring is determined by whether an __________ fertilizes the oocyte

Answer 41

X or Y bearing sperm

Question 42

Chromosomal sex

Answer 42

Determined at fertilization

Question 43

Gonadal sex

Answer 43

Determined by presence of XY chromosome

Question 44

Phenotypic sex

Answer 44

Determined by secretion of testosterone to suppress estrogen

Question 45

Head

Answer 45

Contains the DNA | - acrosome cap contains enzymes which aid in fertilization

Question 46

Midpiece

Answer 46

Contains mitochondria which produce power for the tail action

Question 47

Tail

Answer 47

Flagellum like action provides movement | - 1-4 mm/minute in fluid environment

Question 48

Semen

Answer 48

Name given for the sperm and associated fluids which are ejaculated - all spermatozoa plus fluid from accessory sex glands

Question 49

Accessory sex glands

Answer 49

- ampulla - prostate - seminal vesicles - bulbourethral glands

Question 50

Oogenesis

Answer 50

Development of the oocyte

Question 51

When do oogonia undergo mitosis?

Answer 51

During prenatal growth

Question 52

Oogonia enter meiosis near the time of _______

Answer 52

Birth - remain in resting prophase until puberty - meiosis then resumes in a few cells each cycle

Question 53

Following oogenesis, ____ ovum and _____ polar bodies are produced

Answer 53

1; 3

Question 54

A secondary oocyte is capable of fertilization ________

Answer 54

Immediately | - exception: dogs ovulate a primary ooctye that is not capable of fertilization for 2 days

Question 55

Differences in germ cell production

Answer 55

- males constantly replenish germ cells thru ongoing mitosis - females are born with all they will ever have and slowly deplete their supply - great increase in number of sperm by mitosis in the male - oogenesis involves limited number of oogonia each cycle