1.2 Origin of the Gametes Flashcards
What is the name of the female gamete?
Ovum
What is the name of the male gamete?
Sperm cell
Describe the process of meiosis
A cell splits into 4 haploid daughter cells
What is crossing over in meiosis?
Swapping of genetic material between chromosomes to increase genetic variation
Give 3 ways of increasing genetic variation
Crossing over
Independent assortment
Random segregation
What is the starting material in spermatogenesis?
Spermatogonia
Give the two products of mitosis of spermatogonia
Ad spermatogonium (regenerate stock) Ap spermatogonium (become spermatocytes)
What is spermiation?
Release of spermatids into the seminipherous tubules
When do spermatids become spermatagoa?
When they are remodelled in the rete testis, ductus efferentes and epididymis
Process called spermiogenesis
What is the spermatogenic cycle?
The time taken for the reappearance of the same stage of maturartion of sperm within a given segment of the tubule (about 16 days)
What is the spermatogenic wave?
Distance between the same stage of maturation in the seminipherous tubule
How much semen is in the final ejaculate?
About 2ml
What % makes up the seminal vesicle contribution to semen?
70%
What is found in the seminal vesicle secretions?
Fructose
Amino acids
Citrate
Prostaglandins
What is found in the prostatic secretions in semen?
Proteolytic enzymes
Zinc
What is found in the bulbourethral secretions in semen?
Mucoproteins
What is capacitation of sperm?
Removal of glycoproteins and cholesterol from the sperm membrane. Ativation of sperm signalling pathways and alllows the sperm to bind to the zona pellucida of the ovum
When does capacitation of sperm occur?
When it enters the female reproductive tract
What is the starting organism for oogenesis?
Oogonia
What is a primary oocyte?
Oogonia going through meiosis but stopped in prophase I
Describe a primary follicle
Primary oocyte surrounded by a layer of follicular cells
Describe the change in numbers of oocytes present in the ovary from fertilisation to puberty
- Oogonia proliferate massively by mitosis- 7 million
- Cell death (atresia)- 2 million at birth
- Childhood atresia- 40,000 by puberty
What happens in the pre-antral phase of oocyte development?
Primordial follicles start to grow
Follicular cells change from squamous cells to cuboidal cells
They then proliferate to become a stratified cuboidal layer called granulosa cells
The granulosa cells produce an outer glycoprotein cell called the zona pellucida
What happens in the antral phase of oocyte development?
Fluid filled spaces appear between the granulosa cells which coalesce to form the antrum
What happens in the preovulatory phase of oocyte development?
Surge in LH
Meiosis I is now completed resulting in 2 haploid cells of unequal size
The cell enters meiosis II but stops in metaphase II
What stimulates ovulation?
Rise in LH and FSH
What is the mature oocyte now called?
Graafian follicle
What is the corpus luteum?
Remaining granulosa and theca interna cells within the ovary after the oocyte has been released into the fallopian tubes. They change into lutein cells which secrete oestrogen and progesterone
How does the oocyte travel from the ovary to the uterus?
Fimbriae sweep up the oocyte from the ovary and into the fallopian tube. The fallopian tubes have peristaltic contractions which push the oocyte along, helped by the cillia on the epithelial lining
What is the corpus albicans?
Degeneration of the corpus luteum to a mass of fibrotic scar tissue
In fertilisation how is the corpus luteum maintained?
Human chorionic gonadotrophin (hCG) from the embryo maintains the corpus luteum so it keeps secreting progesterone
