Gametogenesis

Gametogenesis

Physiology of reproductive system

Ms. Beatriz Duro 3º ESO

Human genetic material

• DNA is a large molecule

which coils up into a

structure called

chromosome when the

cell is about to divide.

– When the cell is not

dividing it is loose in the

nucleus in the form of

chromatin.

• DNA contains the genetic

information which

controls cell processes.

Human genetic material

• All human somatic

cells have 46

chromosomes (23

pairs).

– Diploid cells: cells with

pairs of chromosomes.

• Gamets have 23

chromosomes in total.

– Haploid cells: cells with

only one chromosome

of each type.

This is the

human

karyotype

Human cell division

Somatic cells (2n) divide

to form two identical cells

(2n) of the same kind

through mitosis

A special somatic cell (2n)

divides to form four cells

with half the genetic

material (n) through

meiosis

2 types of cell

division:

Spermatogenesis

Growth and

replication of DNA

Meiosis

Maturation

Spermatogenesis

• Maturation

– Takes place in the

epididymis.

– The cell elongates.

– The cytoplasm is reduced.

– The nucleus is set at the

front of the cell together

with the acrosome.

– The flagellum is formed.

Male gamet: sperm

Female gamet: ovum

Oogenesis

Ovarian cycle

Follicularphase

Caused by the secretion of FSH by the pituitary gland.

Lasts 14 days

Various follicles begin to develop, however only one matures

Ovulation The ovum is released by the ovary.

Cause by the presence of LH

The body temperature increases 0.5ºC

Lutealphase

The area where the ovum was, tranforms into a mass of cells: corpus luteum.

Corpus luteum secretes progesterone for 10-12 days.

When it stops secreting hormone the cycle begins again.

Begining of thecycle.

Sharp decrease in the amount of hormones secretedby the ovaries.

Vascularized uterinewall is shed and expelled from thebody: period.

Lasts 4-5 days

Menstrual phase (Period)

Uterine wall is rebuiltthanks to estrogensproduced by theovaries.

Lasts 11 days.

Proliferativephase

Uterine lining is at itsmaximum thickness, ready to receivefertilised egg.

Due to theprogesteronesecreted by theovaries.

Lasts 12 days iffertilization does notoccur

Secretoryphase (Luteal)

Uterine cycle

Menstrual and Ovarian cycles