Lab 1 --Z3332337 11:49, 25 July 2012 (EST)
ANAT2341 – LAB 1 25/07/12
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- The type of cells in the zona radiata are the ‘granulosa’ cells.
- Zona pellucida is a specific extracellular matrix to the (development) of the oocyte. Consists of 3-4 thick glycoproteins made by the oocyte itself and the granulosa cells are attached to the outside.
- The fusion of the spermatozoa to the zona pellucida stimulates the oocyte to continue into the final stages of meiosis.
- The production of the final polar body (which contains half the chromosomes of the original germ cell) is also stimulated.
Occasionally, the 3rd polar body is made by the 1st polar body which also undergoes meiosis. NB: The polar bodies are “trash bags” of the oocytes.
- In meiosis the abnormality trisomy 21 (down syndrome) “leaves behind chromosome 21” (ie: isn’t separated properly).
Two other trisomy’s exist, trisomy’s 18 & 13 (occur in this order). Major genetic abnormalities are spontaneously aborted in the first 2 weeks of development because they are incompatible with proper development.
- The proliferating spermatagonia (make MORE spermatogonia which) are the ones who continue on to complete meiosis, which create spermatids (haploid cells).
- These daughter cells are initially cross-linked until maturation of spermatid into spermatozoa.
- FINAL (functional) MATURATION, doesn’t occur in the epididymis (although altered here).
It actually occurs after ejaculation into the vagina where it undergoes capacitation. The pH in the vaginal canal causes this change.
Sperm undergo morphological, physiological and biochemical changes during the journey through the female reproductive tract; a process called Capacitation.
Semen contains factors that do not allow the sperm to penetrate the ovum and these are removed in the female reproductive tract.
Capacitation needs to occur before the sperm are capable of penetrating and fertilising an ovum.
Many sperm are required to dissolve the zona pellucida of the ovum, but only one gets the chance to fertilize.
- NB: the ovary is located in the PERITONEAL CAVITY.
- Ovarian follicle atresia: atresia refers to the degeneration and subsequent resorption of one or more immature ovarian follicles.
NB: this can happen at any time in the cyle.
- The medullary region of the ovary is highly vascularized because hormones (FSH and LH) are being brought in to regulate menstruation and pregnancy (negative feedback loop).
Supported by the granulosa cells.
Follicle Classification The above images show the histological changes that occur with follicle development (folliculogenesis). In humans, this entire process occurs over the timecourse of at least 3 menstrual cycles. This means that within the ovary during each cycle (at any point in time) many follicles can be either developing (folliculogenesis), regressing (atresis) and only a single follicle will be selected as ready for release. The selected follicle readied for release, generally one of the largest antral follicle, and can be classifed or described as: an antral preovulatory follicle or Graafian follicle or type 8 follicle (depending upon the classification used).
Classification systems - There are several different nomenclatures for the stages of follicle maturation (shown below) all of which makes the literature very confusing. The simplest is primordial, preantral, antral, Preovulatory (Graffian). You can also use the 5 step follicle classification: Primordial, Primary, Secondary, Tertiary, Preovulatory. Note that some classifications refer to the antral follicle as a secondary follicle and do not use the term tertiary follicle.
- Primordial Follicle - Alternative nomenclature: small follicle or type 1, 2, 3 (25 cells) less than 50 micron diameter.
- Preantral Follicle - Alternative nomenclature: preantral follicle or type 4 (26-100 cells), type 5 (101-300 cells) up to 200 micron diameter.
- Antral Follicle - Alternative nomenclature: small antral type 6 (301-500 cells), large antral type 7 (501-1000 cells) small antral 500 micron diameter, large antral 1000-6000 micron diameter.
- Preovulatory Follicle - Alternative nomenclature: largest antral follicle or Graafian follicle or type 8 (>1000 cells) greater than 6000 micron diameter.
NB: IT TAKES MORE THAN 1 CYCLE TO MATURE TO BE SELECTED TO BE RELEASED IN OVULATION.
- Microtubule organisational centre radiates for motility.
- Acrosome (‘acrosomal head’) is a modified golgi apparatus.
Acrosome is a large vesicle, containing enzymes and proteins that enable sperm to penetrate oocyte by dissolving the zona pellucida.
- Mitochondria are tightly packed within the mid-tail of the spermatozoa to generate the ATP required to drive the whip-like movements of the tail.
- There are 3 types of cells: germ, support and hormonal.
- Only 2 cells (sertoli and spermatogonia).