BGDA Practical 3 - Gametogenesis: Difference between revisions
mNo edit summary |
mNo edit summary |
||
Line 253: | Line 253: | ||
{{Cell Division terms}} | {{Cell Division terms}} | ||
{{Oocyte terms}} | |||
{{Glossary}} | |||
<br> | <br> | ||
==References== | ==References== |
Revision as of 12:13, 7 May 2018
Practical 3: Oogenesis and Ovulation | Gametogenesis | Fertilization | Early Cell Division | Week 1 | Implantation | Week 2 | Extraembryonic Spaces | Gastrulation | Notochord | Week 3 |
Female Gametogenesis
In females, the total number of eggs ever to be produced are present in the newborn female.
- All eggs are arrested at an early stage of the first meiotic division as a primary oocyte (primordial follicle). Following purberty, during each menstrual cycle, pituitary gonadotrophin stimulates completion of meiosis 1 the day before ovulation.
- In meiosis 1, a diploid cell becomes 2 haploid (23 chromosomes) daughter cells, each chromosome has two chromatids. One cell becomes the secondary oocyte the other cell forms the first polar body.
- The secondary oocyte then commences meiosis 2 which arrests at metaphase and will not continue without fertilization.
- At fertilization meiosis 2 completes, forming a second polar body. Note that the first polar body may also undergo this process forming a third polar body.
A mouse oocyte undergoing meiosis spindle migration followed by first polar body extrusion and MII spindle positioning.[1]
The video shows that cytoplasmic streaming continues to the MII arrest stage to maintain the oocyte set of chromosomes/MII spindle in place close to the cortex. Frames are 11 min apart, and video length is 840 min. Bar, 20 µm. |
Meiosis and Oogenesis[2] |
Meiosis - divided into 3 temporally distinct phases.
|
Female Abnormalities
Meiotic non-disjunction resulting in aneuploidy, most are embryonic lethal and not seen. The most common non-lethal abnormality is Trisomy 21 or Down syndrome. The potential for this and most genetic abnormalities increase with maternal age.
Trisomy 21 female karyotype | Turner's Syndrome karyotype |
|
|
Male Gametogenesis
The histology will be covered in a separate Male Histology Practical (support page). In males, sperm continues to be generated throughout life from a stem cell population in the testis. Spermatozoa maturation involves two processes meiosis and spermiogenesis.
Testis - Seminiferous Tubule | |
---|---|
Pre-puberty | Post-puberty |
Cross-sectional view of the seminiferous tubule histology before and after puberty. |
The above figure compares meiosis to the female (the polar bodies have been removed and labelling updated).
Human Spermatozoa Development
- Spermatogenesis process of spermatagonia mature into spermatazoa (sperm).
- Continuously throughout life occurs in the seminiferous tubules in the male gonad- testis (plural testes).
- At puberty spermatagonia activate and proliferate (mitosis).
- about 48 days from entering meiosis until morphologically mature spermatozoa
- about 64 days to complete spermatogenesis, depending reproduction time of spermatogonia
- follicle stimulating hormone (FSH) - stimulates the spermatogenic epithelium
- luteinizing-hormone (LH) - stimulates testosterone production by Leydig cells
Spermiogenesis
Spermatozoa Development (expand to see terms) | ||
---|---|---|
Note there are additional glossaries associated with genital, spermatozoa, oocyte and renal.
See also: Spermatozoa Terms collapse table
|
- Links: Spermatozoa Development | MBoC - Sperm | MBoC - Highly simplified drawing of a cross-section of a seminiferous tubule in a mammalian testis | MBoC - Cytoplasmic bridges in developing sperm cells and their precursors
Puberty
- In humans at puberty, hormonal and morphological changes occur within the gonad and other systems (secondary sex characteristics).
- Within the testis the immature Sertoli cells cease to proliferate and differentiate.
- Spermatogonium (plural, spermatogonia) proliferate and spermatogenesis begins.
- It takes about 70 days for cells to mature from the diploid spermatogonium to a primary spermatocyte.
- This maturation occurs in waves along the seminiferous tubules.
Ejaculate
- release of spermatozoa and accessory gland secretions from the male genital tract (3.5 ml)
- 200-600 million sperm, by volume less than 10 % spermatozoa
- Accessory Gland secretions - 60 % seminal vesicle, 30 % prostate and 10 % bulbourethral
Male Abnormalities
Clinically abnormality studies relate mainly to infertility and inherited genetic disorders.
- Oligospermia - (Low Sperm Count) less than 20 million sperm after 72 hour abstinence from sex
- Azoospermia - (Absent Sperm) blockage of duct network
- Immotile Cilia Syndrome - lack of sperm motility
For spermatozoa genetic abnormalities see of Human Sperm.
Differences in Mammalian Meioses
Female Oogenesis | Male Spermatogenesis | |
Meiosis initiated | once in a finite population of cells | continuously in mitotically dividing stem cell population |
Gametes produced | 1 / meiosis | 4 / meiosis |
Meiosis completed | delayed for months or years | completed in days or weeks |
Meiosis Arrest | arrest at 1st meiotic prophase | no arrest differentiation proceed continuously |
Chromosome Equivalence | All chromosomes exhibit equivalent transcription and recombination during meiotic prophase | Sex chromosomes excluded from recombination and transcription during first meiotic prophase |
Gamete Differentiation | occurs while diploid (in first meiotic prophase) | occurs while haploid (after meiosis ends) |
Practical 3: Oogenesis and Ovulation | Gametogenesis | Fertilization | Early Cell Division | Week 1 | Implantation | Week 2 | Extraembryonic Spaces | Gastrulation | Notochord | Week 3 |
Additional Information
Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page. |
- Male Histology - covered in another practical class.
- Genetic Information - covered elsewhere in your course.
- Mitosis and Meiosis - Cell Biology of mitosis and meiosis covered also in Foundations.
Male Histology
This will be covered in detail in a separate Histology practical class, see supporting page BGDA Practical - Male Reproductive Tract Histology.
From today's class you should have a basic understanding of seminiferous tubule structure in relation to spermatozoa development.
Spermatogenesis Review
<pubmed>26537427</pubmed>
Martin RH. Cytogenetics of Human Sperm. In: Madame Curie Bioscience Database [Internet]. Austin (TX): Landes Bioscience; 2000-2013. Available from: https://www.ncbi.nlm.nih.gov/books/NBK6064/
Genetics
Where genes are located and how they are inherited relate to the chromosome that the gene is located upon, the parental origin of the gene and the dominant/recessive nature of the gene.
- Inheritance Pattern images: Genetic Abnormalities | autosomal dominant | autosomal recessive | X-linked dominant (affected father) | X-Linked dominant (affected mother) | X-Linked recessive (affected father) | X-Linked recessive (carrier mother) | mitochondrial inheritance | Codominant inheritance | Genogram symbols | Genetics
Mitosis and Meiosis
Terms
- autosomal inheritance - some hereditary diseases are described as autosomal which means that the disease is due to a DNA error in one of the 22 pairs that are not sex chromosomes. Both boys and girls can then inherit this error. If the error is in a sex chromosome, the inheritance is said to be sex-linked.
- cascade testing - Clinical genetic term for the testing of genetic relatives for a mutation that has been identified in the first affected family member. Abnormal Development - Genetic
- gene - a sequence of DNA that encodes an individual protein.
- genome - the complete genetic information in the form of DNA available to a specific species.
- Johnsen score - a clinical score (1-10) for assessing spermatogenesis in a human testicular biopsy. Named after the author of the original article. PMID 5527187
- sperm - See spermatozoa. The male haploid reproductive cell, often used generically (and incorrectly) to describe these cells and the fluid of the ejaculate. Term is a shortened form of scientifically correct term spermatazoa.
- sperm annulus - (Jensen's ring; Latin, annulus = ring) A region of the mammalian sperm flagellum connecting the midpiece and the principal piece. The annulus is a septin-based structure formed from SEPT1, 4, 6, 7 and 12. Septins are polymerizing GTPases that can act as a scaffold forming hetero-oligomeric filaments required for cytokinesis and other cell cycle roles.
- spermatid - Intermediate cell in spermatozoa development, within the testis seminiferous tubule they lie in the luminal cell layer to the secondary spermatocyte. These small cells are haploid and in spermiogenesis change their cellular structure and shape to form spermatozoa.
- spermatogenesis - (Greek, genesis = origin, creation, generation) The term used to describe the process of diploid spermatagonia division and differentiation to form haploid spermatazoa within the testis (male gonad). The process includes the following cellular changes: meiosis, reoorganization of DNA, reduction in DNA content, reorganization of cellular organelles, morphological changes (cell shape). The final process of change in cell shape is also called spermiogenesis.
- spermiogenesis - (Greek, genesis = origin, creation, generation) The maturation process of the already haploid spermatids into the mature spermatozoa shape and organization. This process involves reorganization of cellular organelles (endoplasmic reticulum, Golgi apparatus, mitochondria), cytoskeletal changes (microtubule organization) and morphological changes (cell shape, acrosome and tail formation). The process of maturation of the spermatids into spermatozoa: chromatin condenses, nucleus becomes smaller, the Golgi apparatus is modified to form the acrosome, microtubules are reorganised to form the tail, mitochondria are relocated to the initial segment of the tail and the majority of cell cytoplasm is discarded.
- spermatogonia - These cells form in the embryo from the primordial germ cell and are located in the seminiferous tubule adjacent to the basal membrane. The cells can either divide and separate to renew the stem cell population, or they divide and stay together as a pair (Apr spermatogonia) connected by an intercellular cytoplasmic bridge to begin to differentiate and eventually form spermatazoa.
- spermatozoa - (spermatozoon, singular term) The male haploid gamete cell produced by meiosis in the testis (male gonad) seminiferous tubule. In humans, produced from puberty onwards and develop from the diploid stem cell the spermatogonia. The developmental meiosis is called spermatogenesis and the final morphologiccal (shape) change is called spermeiogenesis. The mature human spermatozoon formed from the spermatid has a head, neck and tail and is about 60 µm long. At ejaculation these cells undergo capacitation are activated and become motile.
- spermatozoa head - Following spermiogenesis, the first region of the spermatozoa containing the haploid nucleus and acrosome. In humans, it is a flattened structure (5 µm long by 3 µm wide) with the posterior part of nuclear membrane forming the basal plate region. The human spermatozoa is about 60 µm long, actively motile and divided into 3 main regions (head, neck and tail).
- spermatozoa neck - Following spermiogenesis, the second region of the spermatozoa attached to basal plate, transverse oriented centriole, contains nine segmented columns of fibrous material, continue as outer dense fibres in tail. In humans, it forms a short structure (1 µm). The human spermatozoa is about 60 µm long, actively motile and divided into 3 main regions (head, neck and tail).
- spermatozoa tail - Following spermiogenesis, the third region of the spermatozoa that has a (head, neck and tail). The tail is also divided into 3 structural regions a middle piece, a principal piece and an end piece. In humans: the middle piece (5 µm long) is formed by axonema and dense fibres surrounded by mitochondria; the principal piece (45 µm long) fibrous sheath interconnected by regularly spaced circumferential hoops; the final end piece (5 µm long) has an axonema surrounded by small amount of cytoplasm and plasma membrane.
- spermatogonial stem cells - (SSCs) The spermatagonia cells located beside the seminiferous tubule basal membrane that either divide and separate to renew the stem cell population, or they divide and stay together as a pair (Apr spermatogonia) connected by an intercellular cytoplasmic bridge to differentiate and eventually form spermatazoa.
- sperm protein 56 - A component of the spermatozoa acrosomal matrix released to the sperm surface during capacitation.
Spermatozoa Development (expand to see terms) | ||
---|---|---|
Note there are additional glossaries associated with genital, spermatozoa, oocyte and renal.
See also: Spermatozoa Terms collapse table
|
Cell Division Terms (expand to view) | ||
---|---|---|
meiosis | mitosis
| ||
|
Note there are additional specific term glossaries available listed at bottom of this table.
- antral follicle - (secondary) the stage following preantral in the decription of the sequence ovarian follicle development.
- antrum - (L. a cave), cavity; a nearly-closed cavity or bulge. In the ovary this refers to the follicular fluid-filled space within the follicle.
- atretic follicle - An ovarian follicle that fails to mature and degenerates. Also called "atresia" refering to the process of degeneration of the ovarian follicle. This process can occur at any stage of follicle development (folliculogenesis).
- clomiphene citrate - drug taken orally to promote the process of follicle/egg maturation.
- COCs - (cumulus-oocyte complexes) term used in Assisted Reproductive Technology to describe the ovulated Graafian follicle consisting of the oocyte surrounded by a packed layers of cumulus cells.
- corona radiata - Layer of follicle cells of cumulus oophorus remaining directly attached to zona pellucida of the oocyte. These cells communicate with the oocyte through the zone pellucida, also called granulosa cells.
- corpus albicans - (L. corpus = body, L. albicans = whitish); a degenerating corpus luteum in ovary.
- corpus luteum - (L. corpus = body, L. luteum = yellow) The remains of the ovulating ovarian follicle after ovulation, that acts as the initial endocrine organ supporting pregnancy and preventing menstruation (loss of the endometrial lining). de Graaf first observed it in the ovary of a cow as a yellow structure.
- cortical - (L. corticalis) at the outside (like the bark of a tree), usually combined with medulla meaning the core.
- cumulus oophorus - (L. cumulus = a little mound G. oon = egg + phorus = bearing); part of the wall of an ovarian follicle surrounding and carrying the ovum (oocyte).
- dictyate arrest - (prophase arrest) the oocyte meiosis state before puberty resumed with a surge of pituitary luteinizing hormone.
- first polar body - a small cytoplasmic exclusion body contains the excess DNA from the oocyte meiosis formed during meiosis 1.
- follicle - (L. folliculus = little bag,dim. of L. follis). A structure which develops in the ovary and contains a developing egg (oocyte).
- follicle stimulating hormone - (FSH, gonadotropin) A glycoprotein hormone secreted by anterior pituitary (adenohypophysis gonadotrophs, a subgroup of basophilic cells) and acts on gametogenesis and other systems in both males and females. Females, FSH acts on the ovary to stimulate follicle development. Males, acts on the testis Sertoli cells to increase androgen-binding protein (ABP) that binds androgens and has a role in spermatogenesis. pituitary
- follicular fluid - the fluid found in the antrum of a secondary follicle. Secreted by cells in the wall of the follicle. This fluid is released along with the oocyte at ovulation.
- germinal epithelium - cellular component covering surface of ovary, it is continuous with mesothelium covering mesovarium. Note that it is a historical misnomer, as it is not the actual site of germ cell formation.
- Graafian follicle - named after Regnier de Graaf (1641-1673), an historic Dutch physician embryologist who studied pregnancy using rabbits.
- granulosa cells - the supporting cells that surround the developing egg within the follicle thecal layers.
- homologs - maternal and paternal homologous chromosomes.
- Izumo1 - a protein located on the equatorial segment of acrosome-reacted spermatozoa recognizes its receptor Juno, on the oocyte surface, for plasma membrane binding and fusion. Named for a Japanese shrine dedicated to marriage. OMIM609278
- Juno - (folate receptor-δ; FOLR-δ) a glycophosphatidylinositol (GPI)-anchored, cysteine-rich glycoprotein on the oocyte surface for fertilisation that is the receptor of Izumo1 on the spermatozoa, for plasma membrane binding and fusion. OMIM615737
- luteinizing hormone - (LH, gonadotropin, lutropin, Interstitial Cell Stimulating Hormone, ICSH) glycoprotein hormone releasd from anterior pituitary hormone that acts on the gonad and has a role in male and female reproduction. Female, LH triggers ovulation (release of the oocyte). Male, LH stimulates testis interstital cell (Leydig cell) production of testosterone. Have been used clinically in humans for the treatment of female infertility.
- meiosis - oocyte reductive (diploid to haploid) cell division, with 1 round of DNA replication is followed by 2 rounds of chromosome segregation. The process beginning in the fetus and only completed at fertilization.
- mesovarium - mesentry of the ovary formed from a fold of the broad ligament that attaches the ovary.
- medullary - (L. medius = in the middle) relating to the medulla; pith, marrow, inner portion of an organ. Usually combined with cortex (cortical) meaning the outer layer.
- oocyte - (Greek, oo = egg, ovum) The term used to describe the haploid egg or ovum formed within the ovary (female gonad) and released to enter the uterine tube and be transported to the uterus. The mature oocyte is the cell released from the ovary during ovulation.
- oocyte retrieval - (egg retrieval) A clinical in vitro fertilization (IVF) procedure to collect the eggs contained in the ovarian follicles.
- oogenesis - (Greek, oo = egg + genesis = origin, creation, generation) process of diploid oogonia division and differentiation into an haploid oocyte (egg) within the ovary (female gonad). Mammalian meiosis will only be completed within the oocyte if fertilization occurs.
- oogonia - (Greek, oo = egg) diploid germ cells within the ovary (female gonad) which provide the primary oocytes for oocyte (egg) formation. In humans, all oogonia form primary oocytes within the ovary before birth.
- oolemma - (zona pellucida, vitelline membrane).
- oophorus - (Greek, oo = egg + phorus = carrying, egg-bearing) cumulus oophorus, used to describe the granulosa cells within the follicle that tether or link the oocyte to the wall of the follicle.
- ovarian reserve - Clinical term for the number of oocytes (non-growing follicles) available for possible fertilization at the different times during female reproductive life. A blood test for Anti-Mullerian Hormone (AMH) levels is used clinically as a measure of the ovarian reserve. human graph
- ovastacin - an oocyte released enzyme following fertilization that cleaves ZP2 protein to prevent polyspermy.
- ovulation - release of the oocyte from the mature follicle. In humans generally a single oocyte is released from a cohort of several maturing follicles.
- ovum - oocyte, note that historically this same term was also used to describe the early stages following fertilisation.
- polar body - small cytoplasmic exclusion body contains the excess DNA from the oocyte meiosis reductive division. The first polar body formed during meiosis 1, the second and sometimes third polar bodies are formed from meiosis 2 at fertilization.
- polyspermy - abnormal fertilization by more that a single spermatozoa, may generate a hydatidiform mole.
- preantral follicle - (primary) the stage following primordial in the description of the sequence ovarian follicle development.
- primary follicle - (preantral) the stage following primordial in the description of the sequence ovarian follicle development.
- primordial follicle - the first stage in the description of the sequence ovarian follicle development. Present in the ovary from birth, located in the stroma of the ovary cortex beneath the tunica albuginea. The primordial follicle is the oocyte and the surrounding follicular cells.
- primordial germ cell - oocyte present in the primordial follicle ovary from birth, located in the stroma of the ovary cortex beneath the tunica albuginea. The primordial follicle is the oocyte and the surrounding follicular cells.
- second polar body - a small cytoplasmic exclusion body contains the excess DNA from the oocyte formed during meiosis 2 at fertilization.
- secondary follicles - the stage following primary in the description of the sequence ovarian follicle development.
- stromal cells - in the ovary, cells surrounding the developing follicle that form a connective tissue sheath (theca folliculi). This layer then differentiates into 2 layers (theca interna, theca externa). This region is richly vascularized and involved in hormone secretion.
- superovulation therapy - a fertility drug treatement (oral clomiphene citrate and/or injectable FSH with or without LH) aimed at stimulating development/release of more than one follicle during a single menstrual cycle.
- tertiary follicle - (preovulatory, Graffian) the stage following secondary in the description of the sequence ovarian follicle development.
- theca folliculi - stromal cells in the ovary, cells surrounding the developing follicle that form a connective tissue sheath. This layer then differentiates into 2 layers (theca interna, theca externa). This region is vascularized and involved in hormone secretion.
- theca externa - stromal cells forming the outer layer of the theca folliculi surrounding the developing follicle. Consisting of connective tissue cells, smooth muscle and collagen fibers.
- theca interna - stromal cells forming the inner layer of the theca folliculi surrounding the developing follicle. This vascularized layer of cells respond to LH (leutenizing hormone) synthesizing and secreting androgens which are processed into estrogen.
- transzonal projection - (TZP) ovarian follicle term describing the cellular membraneous extension from the granulosa cell through the zona pellucida to the oocyte cell membrane where it forms gap junctions or adherens junctions allowing signalling and adhesion between the two cells.
- tunica albuginea - dense connective tissue layer lying near the ovary surface, a layer of simple squamous to cuboidal epithelial covers this layer. A similar named structure is found in male genital system.
- uterus - site of embryo implantation and development. Uterine wall has 3 major layers: endometrium, myometrium, and perimetrium. Endometrium can be further divided into the functional layer (shed/lost during menstruation) and basal layer (not lost during menstruation).
- zinc sparks following fertilization the oocyte releases a burst of zinc atoms in brief bursts (zinc sparks) has a role in zonal pellucida induced structural changes (hardening) along with ovastacin cleavage of ZP2 protein.
- zona hardening - following fertilization the structural changes that occur to the zona pellucida to prevents further spermatozoa binding acting as a block to polyspermy.
- zona pellucida - extracellular layer lying directly around the oocyte underneath follicular cells. Has an important role in egg development, fertilization and blastocyst development. This thick extracellular matrix consists of glcosaminoglycans and 3 glycoproteins (ZP1, ZP2, ZP3). (More? Zona pellucida)
Other Terms Lists |
---|
Terms Lists: ART | Birth | Bone | Cardiovascular | Cell Division | Endocrine | Gastrointestinal | Genital | Genetic | Head | Hearing | Heart | Immune | Integumentary | Neonatal | Neural | Oocyte | Palate | Placenta | Radiation | Renal | Respiratory | Spermatozoa | Statistics | Tooth | Ultrasound | Vision | Historic | Drugs | Glossary |
Glossary Links
- Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link
References
- ↑ Yi K, Rubinstein B, Unruh JR, Guo F, Slaughter BD & Li R. (2013). Sequential actin-based pushing forces drive meiosis I chromosome migration and symmetry breaking in oocytes. J. Cell Biol. , 200, 567-76. PMID: 23439682 DOI.
- ↑ Nagaoka SI, Hassold TJ & Hunt PA. (2012). Human aneuploidy: mechanisms and new insights into an age-old problem. Nat. Rev. Genet. , 13, 493-504. PMID: 22705668 DOI.
Practical 3: Oogenesis and Ovulation | Gametogenesis | Fertilization | Early Cell Division | Week 1 | Implantation | Week 2 | Extraembryonic Spaces | Gastrulation | Notochord | Week 3 |
BGDA: Lecture 1 | Lecture 2 | Practical 3 | Practical 6 | Practical 12 | Lecture Neural | Practical 14 | Histology Support - Female | Male | Tutorial
Glossary Links
- Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link
Cite this page: Hill, M.A. (2024, March 28) Embryology BGDA Practical 3 - Gametogenesis. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/BGDA_Practical_3_-_Gametogenesis
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G