Gametogenesis Flashcards
the male and female sex cells are known as what, generally and specifically?
Gametes
- sperm and oocyte
How many chromosomes do gametes contain? And what is this condition called?
23
haploid
what is the creation of sex cells called, generally and gender-specifically?
Gametogenesis
- spermiogenesis and oogenesis
The first meiotic division is known as what?
Why?
reduction division
because chromosome number is reduced from diploid (46) to haploid (23)
what two phases of which meiotic division result in a halving of the number of chromosomes in the resultant cells?
and how?
**prophase I **- pairing of homologous chromosomes
**anaphase I **- segregation of chromosome pairs created in prophase I
What is the process of the separation of allelic genes called during meiosis?
segregation
- prophase - pairing of homologous chromosomes
- anaphase - pulling apart of pairs
What is the condition of chromosomes after DNA replication?
double chromatid chromosomes
What exists at the start of meiosis II and what is produced as a result?
two haploid cells with double chromatid chromosomes formed during meiosis I become four haploid cells with single chromatid chromosomes
(via division of chromosomes into single chromatids and pulling apart of these “sister” chromatids)
What is the importance of meiosis?
3 points
- constancy of chromosome number - diploid cells become haploid gametes
- random genetic assortment - mixing of maternal and paternal chromosomes btwn gametes
- genetic recombination - chromosome crossover “shuffles” genetic material
What is the process of male sex cell maturation called?
When does it begin?
Spermatogenesis
begins at puberty (age 13 to 16)
What are the immature male sex cells which are dormant in the male until puberty?
Where are they dormant?
When did they come into existence and when are more of them created?
**Spermatogonia **(sing. spermatogonium)
- dormant in the seminiferous tubules since the fetal period but more are produced during puberty
What are the germ cells which are formed from spermatogonia?
How are they formed?
How does their size compare to other cells?
What is their chromosome number?
Primary Spermatocytes
are formed mitotically and are the **largest **germ cells in the seminiferous tubules
still 46 chromosomes (because only mitosis until now)
What cells are formed from primary spermatocytes?
Via what process?
What is their size, chromosome number and chromosomal gender (X or Y)?
secondary spermatocytes
- are formed via meiosis I and thus have 23 chromosomes
- are about half the size of primary spermatocytes
- one X and one Y form from each primary spermatocyte
What cells are formed from secondary spermatocytes?
Via what process?
What is their size, chromosome number and chromosomal gender?
spermatids
- formed via meiosis II
- half the size of secondary spermatocyte
- 23 chromosomes
- 2 X and 2 Y (formed from 1 X and 1 Y secondary spermatocyte, respectively)
What is the final process by which the four male haploid gametes created via meiosis finish maturing?
What major things occur during this?
spermiogenesis
(not spermatogenesis, which is the whole process from spermatogonium to mature sperm)
- spermatid elongates
- acrosome forms from Golgi region
- mitochondria arrange around middle piece of tail
- extra cytoplasm is shed
How long does the entire process of spermatogenesis take?
What happens to the sperm when it is complete?
2 months
mature sperm enter the lumina of the seminiferous tubules
What are the cells which line the seminiferous tubules and nurture the germ cells?
Sertoli cells
What are the main parts of the sperm?
One of them has 3 pieces. What are they?
- Head
- Neck
- Tail (3 pieces)
- middle (mitochondrial sheath)
- principle
- **end **
What are the general overall steps of oogenesis (including pre-birth steps)?
- **Oogonia **form from primordial germ cells in wall of yolk sac
- Primary oocytes all** **form and begin meiosis I before birth (stuck in prophase)
- **Primordial follicles **form as SSE follicular cells surround oocyte
- Primary follicle forms as follicle grows and foll. cells become cuboidal, then columnar
- **Secondary follicle **forms when foll. cell layers are > 1
- **Tertiary follicle **forms when antrum forms
- Graafian follicle forms as follicle matures completely and is at its largest
- Secondary oocyte and polar bodies form via the rest of meiosis I and leave follicle for ovulation
(Old purple parrots play some tricky games sometimes)
What are the simple squamous epithelial cells which surround primary oocytes called?
follicular cells
What is the resting state of a follicle before it matures during the menstrual cycle after puberty has begun?
primordial follicle
What is the acellular layer which directly surrounds the oocyte called and made of?
What produces it?
Zona Pellucida
- made of glycoprotein
- produced by granulosa cells surrounding oocyte
What are the cells surrounding the oocyte called once there is more than one layer?
granulosa cells
What is the fluid filled space within a follicle called?
What is it filled with?
When does it form?
Antrum
- filled with **liquor folliculi **rich in hyaluronic acid
- forms after secondary follicle and marks transition to tertiary follicle
What is the largest, most mature follicle stage?
How big is it?
Graafian Follicle
1.5 cm
What are the innermost 1-3 cell layers around the oocyte called?
corona radiata
What are the two outer cellular layers of the Graafian follicle called?
Their functions/structural characteristics?
Internal Theca - hormone producing layer
External Theca - fibrocyte-like
What does the Graafian follicle become after ovulation?
And what does it do?
Corpus Luteum
produces progesterone
Identify the numbered parts.

- Primordial Follicle
- Primary Follicle (once granulosa cells > cuboidal)
- Secondary Follicle (once theca cells differentiate)
- Tertiary Follicle (now “antral”)
- Graafian Follicle (~1.5 cm)
- Granulosa Cells (squamous here)
- Primary Oocyte
- Corona Radiata (innermost layer of granulosa cells)
- Zona Pellucida (glycoprotein coat)
- Theca Externa (CT like)
- Theca Interna (receive LH, make androstenedione)
- Antrum (full of Liqour Folliculi)
- Cumulus Oophorus (cluster of cells around oocyte)
What marks the change to (or characterizes) a secondary follicle?
Moore - antrum formation
Wiki - ~9 layers granulosa cells, theca differentiation, ZP