Gametogenesis: Amphibian & Mammalian Spermatogenesis

Question 1

Where does meiosis occur?

Answer 1

Only in the gonads—the ovary and testis—and more specifically, only in the germ cells that are lodged in the gonads.

Question 2

the method of cell division that halves the number of chromosomes in the resulting egg and sperm cells

Answer 2

meiosis

Question 3

Primordial germ cells arrive in the developing gonad after a long trip, often from the far reaches of the ________

Answer 3

yolk endoderm

Question 4

General steps in gametogenesis:

Answer 4

1. Extragonadal origin + migration of PGC
2. Proliferation of germ cells
3. Meiosis
4. Maturation of gametes

Question 5

The spermatids then go through a further differentiation process called ______ to become fully formed spermatozoa.

Answer 5

spermiogenesis

Question 6

During the maturation of gametes, these are the 3 outcomes

Answer 6

1. Blastula
2. Tropoblast (forms the placenta)
3. Inner cell mass (epiblast & hypoblast)

Question 7

Which type of spermatogonia proceeds to become a stem cell and which one will enter meiosis

Answer 7

Type A = Stem cell
Type B = Enters meiosis

Question 8

General steps of spermatogenesis

Answer 8

1. Differentiation and proliferation
2. Meiosis
3. Spermiogenesis

Question 9

What happens during spermiation

Answer 9

1. Acrosome
2. Flagellum formation
3. Nuclear condensation
4. Remove excess cytoplasm
5. Specific mitochondrial arrangement (midline of sperm)
   Streamlined to facilitate movement

Question 10

Found in the acrosome is a hydrolytic enzyme (hyaluronidase) that digests zona pellucida

Question 11

How long does the egg arrive from the fallopian tube to uterus

Answer 11

6 days

Question 12

In humans, external fertilization is called ___________

Answer 12

ampullary-isthmic junction -> site of fertilization

ampulla & isthmus of the fallopian tube

Question 13

a roundish structure surrounded by a tough sheath of connective tissue.

Protective connective tissue layer of testis

Answer 13

Tunica albuginea

Question 13

These tubules should look like little doughnuts. It is in these _________ that the sperm are being produced.

Answer 13

Seminiferous tubules

Question 14

secrete the male sex hormone,
testosterone

Answer 14

interstitial cells, or Leydig cells

Question 15

The human male, for example, can
produce up to ______ sperm per day

Answer 15

300 million

Question 16

a sperm count of less than _____ sperm per ml of ejaculate is tantamount to being sterile.

Answer 16

20 million

Question 17

Other causes of sterility

Answer 17

tight jeans
hot baths,
fevers,

all of which raise the temperature of the testis.

Question 18

Sperm development is extremely temperature-sensitive and can only occur in mammals at a temperature _____________

Answer 18

1.5–2.0°C cooler than normal body temperature

Question 19

Different gonadal stages

Answer 19

1. Recovery stage
2. Growing stage -> maturing
3. Mature stage
4. Partly spawned -> little by little release
5. Spent

Question 20

tunica albuginea consists primarily of extracellular fibers of _______.

Answer 20

type I collagen

Question 21

The cells that make collagen are called

Answer 21

fibroblasts

Question 22

is the epithelium that produces sperm

Answer 22

seminiferous tubule

Question 23

The _______for any epithelium is of major importance to the differentiation and maintenance of that epithelium. It is an acellular layer, made up primarily of type IV collagen, laminin, fibronectin, and heparan sulfate proteoglycan.

Answer 23

basement membrane

Question 24

Nurse cells of spermatogenesis and is responsible for blood-testis barrier

Answer 24

Sertoli cells

The Sertoli cells are nondividing, tall, columnar cells that extend from the basement membrane to the lumen of the tubule. The nuclei of these cells are irregularly shaped and stain lightly, making them easy to identify.

Question 25

As the cells progress through their differentiation, they move closer and closer to the lumen of the tubule. Spermatozoa sit with their tails sticking out into the lumen.

Question 26

Sertoli cells function to support and nourish the germ cells throughout their development. Sertoli cells are also responsible for the translocation of the developing sperm toward the lumen and their eventual release.

Question 27

The entire process of spermatogenesis (from spermatogonium to spermatozoan) takes 48 days in the rat and 64 days in humans.

Question 28

The ____________, lying between the seminiferous tubules constitute the mesenchyme of the testis.

Answer 28

interstitial cells, or Leydig cells

Question 29

In response to leutinizing hormone, LH, the Leydig cells secrete testosterone, which is required both for spermatogenesis and for development of secondary male characteristics.

Question 30

male germ cells undergoing maturation division located inside the spermatocysts.

Answer 30

Spermatogenic Cells

Question 31

small cells with irregular dense
nuclear materials.Their small spermatocyst is interspersed among the bigger spermatocysts. They are inactive in cell division and serve as the reserve cells for the next breeding period.

Answer 31

Residual Spermatogonia

Question 32

large cells close to the periphery of seminiferous tubules. They are actively dividing cells with prominent nuclei and threadlike chromatin materials.

Answer 32

Active Spermatogonia

Question 33

cluster of minute cells appearing as clumps of black rods

Answer 33

Spermatozoa

Question 34

columnar or pyramidal cells that adhere to the basement membrane or lying among the germ cells.

Answer 34

Sertoli cells

Question 35

functions of the Sertoli cells.

Answer 35

support and nourish the germ cells throughout their development.

translocation of the developing sperm towards the lumen

blood-testis barrier