When does human development begin?
When an oocyte (ovum) from a female is fertilized by a sperm (spermatozoon) from a male.
When are gametes derived?
From primordial germ cells formed in the epiblast during the 2nd week of life
When does Meiosis occur?
Only during the production of gametes (sex cells). Consists of two cell divisions (meiosis I and meiosis II) and results in the formation of gameted containing 23 chromosomes.
Outline the steps for Meiosis 1 and 2
Prophase 1: The chromosomes condense, and the nuclear envelope braks down. Crossing over occurs.
Metaphase 1: Pairs of homologous chromosomes move to the equator of the cell.
Anaphase 1: Homologous chromosomes move to the opposite poles of the cell.
Telophase 1 & Cytokinesis: Chromosomes gather at the poles of the cells. The cytoplasm divides.
Prophase 2: A new spindle forms around the chromosomes.
Metaphase 2: Metaphase 2 chromosomes line up at the equator
Anaphase 2: Centromeres divide. Chromatids move to the opposite poles of the cells.
Telophase 2 and Cytokinesis: A nuclear envelope forms around each set of chromosomes. The cytoplasm divides.
What is Gametogenesis?
Gametogenesis is the process of formation and development of gametes.
When do primordial germ cells reach the ovary and what do they become?
They reach the ovary at week 6 of embryonic development and become ooginia
When does spermatogenesis begin, and when are spermatogonia found?
It begins at puberty. Spermatongia are dormant in the seminiferous tubules during fetal and postnatal life, and then multiply at puberty.
What divisions occur during spermatogenesis?
Primary spermatocytes undergo the first meiotic division to form two secondary spermatocytes, which undergo a second meiotic division to produce four haploid spermatids.
What is spermiogenesis and how long does the whole process take?
Spermiogenesis is the transformation of spermatids into mature sperm, and the entire spermatogenesis process takes about 2 months.
What cells line the seminiferous tubules?
Sertoli Cells. They support and nurture the germ cells.
What is the epididymis?
An elongated coiled duct along the posterior border of the testis. Here, sperms are stored and become functionally mature during puberty.
What transports the sperms to the urethra?
The ductus deferens
What do the enzymes in the acrosome of the sperm assist in?
Facilitate dispersion of the follicular cells of the corona radiata and sperm penetration of the zona pellucisa during fertilization.
What are the 3 segments of the tail of the sperm?
Middle piece (contains mitochondria), principal piece and end piece
What is the oocyte surrounded by?
The zona pellucida and a layer of follicular cells, the corona radiata
What is the ideal biological maternal age for reproduction?
18-35 years
What are the 3 layers of the uterus?
- Perimetrium - thin external layer
- Myometrium - thick smooth muscle layer
- Endomerium - thin internal layer
Uterine tubes are also known as?
Fallopian tubes
What are the 4 parts of the uterine tube?
Infidibulum, ampulla, isthmus and uterine part
What is the name of the fertilization site in the uterine tube?
The ampulla
What are the functions of the ovaries?
- Produce oocytes
- Produce estrogen and progesterone
What are the organs involved in the Ovarion Cycle?
The hypothalamus of the brain, pituitary gland, ovaries, uterus, uterine tubes, vagina, and mammary glands
What are the 2 hormones released by the stimulation of GnRH?
- Follicle - stimulating hormone (FSH) - stimulates the development of ovarion follicles and the production of estrogen by the follicular cells.
- Luteinizing hormone (LH) serves as the ‘trigger’ for ovulation (release of secondary oocyte) and stimulates the follicular cells and corpus luteum to produce progesterone.
What is ovulation?
The expulsion of the oocyte.
