Hormones and Gametes Flashcards
(36 cards)
What is a gamete?
Sperm or ova
Specialised cells that allow us to ass our genes on to the next generation
What type of cell is a gamete?
Haploid cell
23 individual chromosomes
What are gametes derived from?
Germ cells
Migrate to the gonads at about 6 weeks of development
After colonising the gonad, the germ cells:
Proliferate
Reshuffle genetic material
Reduce to haploid
Mature into sperm
List the phases of mitosis
Interphase (G2)
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
What happens in interphase (G2)
2 copies of centrosome
DNA has replicated
What happens in prophase?
Chromosomes condense
Mitotic spindle poles forms
Nucleus wall starts to break down
What happens in prometaphase?
Chromosomes condense
Microtubules start to capture chromosomes at the kinetochore
What happens in metaphase?
All chromosomes are captured
Line up at metaphase
What happens in anaphase?
Microtubules push poles apart making the cell bigger
Where are spermatogonia cells found?
XY germ cells colonise medulla of testes in male embryo
Cells proliferate (mitosis) to form spermatogonia
Cords hollow out to form seminiferous tubules
Spermatogonia cluster around the edges of seminiferous tubules
Discuss spermatogenesis
At puberty, a group of spermatogonia divide by mitosis a fixed number of times to form 64 linked diploid cells called primary spermatocytes
Meiosis I produces two haploid secondary spermatocytes
Meiosis II results in four haploid spermatids per primary spermatid
Discuss spermatogenesis
At puberty, a group of spermatogonia divide by mitosis a fixed number of times to form 64 linked diploid cells called primary spermatocytes
Meiosis I produces two haploid secondary spermatocytes
Meiosis II results in four haploid spermatids per primary spermatid
Spermatagonia are constantly replaced at the edge of seminiferous tubules
Spermatids are close to lumen
Discuss spermiogenesis
Maturation of spermatids into differentiated spermatozoa
Spermatids are released into tubule + undergo remodelling/maturation as the pass through the testes, efferent duct and epididymis
What are the major morphological changes that occur during spermiogenesis?
Formation of a head containing the nucleus and a mid-piece containing mitochondria
Formation of the acrosome from Golgi apparatus
Elongation of one centriole to form a tail
Loss of excess cytoplasm
What role does the acrosome of the spermatozoa have?
Contains digestive enzymes that break down the zona pellucida, a glycoprotein layer that surrounds the ovum
Why does spermatozoa contain lots of mitochondria?
To provide energy for swimming
How often are spermatogonia recruited?
Every 16 days
How long does the process of spermatogenesis and spermiogenesis take?
70 days
What 4 things does semen contain?
Secretions of seminal vesicle (60%)
Secretions of the prostate (20%)
Sperm
Secretions of bulbo-urethral glands
Discuss the process of oogonia
XX germ cells colonise the cortex of the ovaries
Proliferate by mitosis forming oogonia
2 million oogonia remain at the end of gestation
They all enter meiosis before birth
Female has developed all stock of potential gametes before birth
Discuss the process of oogenesis
Meiosis stops at early stage resulting in diploid primary oocyte
From puberty, each month a primary oocyte complete development to form mature ovum
Meiotic division only resumes at ovulation
Meiosis I produces haploid secondary oocyte and polar body
Meiosis II produces mature ovum and second polar body
Successful reproduction requires:
Fertilisation
A system of support for the conceptus, embryo and foetus
Birth at the right time
Successful reproduction requires:
What is it controlled by?
Fertilisation
A system of support for the conceptus, embryo and foetus
Birth at the right time
Controlled by the HPG axis
