Gametogenesis and Fertilization Flashcards
Embryology of the gonads
Embryology of the Gonads
Primordial germ cells= progenitors of gametes
- Origin: yolk sac endoderm
- migrate to genital ridge (which will become indifferent gonad)
Intermediate mesogerm= gives rise to part of urogenital organs
Urogenital sinus endoderm= gives rise to terminal genital organs
- vesicular, prostate, bulbourethral glands
MALE AND FEMALE GONAD DEVELOPMENT DIVERGES
Mullerian Ducts (Paramesonephric ducts)
- In females…become fallopian tubesm uterus, and cervix
- In males… dissapear due to anti-paramesonephric hormone
Prepuberal Testis
Prepuberal Testis
Seminiferous cords made of
- Sertoli cells
- primordial germ cells- dormant till pubertly. stem cells for spermatogenesis
Inactive interstitial cells of Leydig
Descent of testis: normal and abnormal
Descent of testis:normal
watch video and answer questions…
Descent of testis: abnormal
Cryptorchidism= testes fail to descend into scrotum.
- inherited sex-limited autosomal recessive trait
Scrotal hernia= inguinal hernia- congenital weakness in the abdominal wall
Steps of Gametogenesis
Gametogenesis
Primative sex cells: Spermatogonia and Oogonia
multiply through Mitosis
Meiosis produces gametes: Spermatocyte and Oocyte
**Fertilization is joining of sex cells- Zygote
mitosis vs. meiosis
Mitosis= division of one cell to form 2 daughter cells with
- Diploid chromisomes
- identicle to mother cell
Meiosis= two divisions!
- first division results in two daughter cells (diploid)
- second division results in four haploid daughter cells
- CROSSOVER in PROPHASE results in variation in gamete
Oogenesis and Spermatogenesis: Similarities (4)
Oogenesis and Spermatogenesis: Similarities (4)
- multiplication of spermatogonia and oogonia
- meiosis
- extensive morphological differentiation
- cannot survive long without fertilization
Oogenesis and Spermatogenesis: Differences (5)
Oogenesis and Spermatogenesis: Differences (5)
Oogenesis
- all oocytes present at birth
- 1 oocyte produces one ovum
- grows from small cell to large cell
- immotile cell
- X chromisomes
Spermatogenesis
- Sperm contilually renewed
- 1 spermatocyte produces 4 sperm
- shrinks from large cell to small cell
- motile cells
- X/Y sex chromosome
Oogenesis: detailed steps (3)
relate to female anatomy
Oogenesis
- Oogonia- prenatal mitosis and differentiation
* primary oocytes(4N) arrested in Meiosis I until puberty - Folliculogenesis- at puberty
* Meiosis I is completed at ovulation - Secondary oocyte (2N + 1 polar body) in uterine tube waits for fertilization
- Meiosis II completed upon sperm contact
- Results in Ovum (1n) and 2nd polar body (1n)
Folliculogenesis
Oogenesis: Folliculogenesis
Folliculogenesis= at puberty, hormone influences folliculogenesis which leads to ovulation.
- primordial follicles= resting
* Oocyte I with single layer of squaous follicular cells - primary follicles= activated/growing follicles
* zona pellucida forms - secondary follicles (secretory)= antral follicles
* formation of fluid filled spaces among granulosa cells - tertiary mature follicle= contains primary oocyte
- one atrum containing liquor folliculi
- eccentric cumulus oophorus
What happens in the ovary post ovulation?
Upon ovulation, oocyte leaves ovary…
_Corpus hemorrhagicum-_is structure that is left behind. It is filled in by luteal cells and becomes the Corpus luteum.
Corpus luteum- produces progesterone and estrogen
- granulosa and theca luteal cells do this
- progesterone maintains pregnancy and locally downregulates the immune system
Corpus albicans- white connective tissue scar that remains when corpus luteum regresses
Identify
Identify
Identify
Spermatogenesis: detailed steps (5)
relate to male anatomy
Spermatogenesis
- Spermatogonium= (2N) mitosis and differentiate
- Primary Spermatocyte= (4N) meiosis I (crossover)
- Two Secondary Spermatocytes= (2N) meiosis II
- Four Spermatids= (1N) Undergo spermiogenesis (no division)
- Four Spermatozoa= Sperm cells!
Sertoli Cells (4)
Spermatogenesis
Sertoli Cells have many functions!
- secrete anti-mullerian hormone during fetal development
- secrete inhibin and activins after puberty to regulate follicle-stimulating hormone
- secrete androgen binding protein to bind testosterne, concentrating it in seminiferous tibules and stimulate spermatogenesis
- provide support, protection and nutriton until spermatids mature
Spermatozoa: structure
Speratozoa= sperm cell
head-caput
- different shape in different species
tail-flagellum
- Axoneme- is pair of microtubules and Dynein arms
Spermatogenesis: issues (6)
Spermatogenesis is sensative to…
- temperature
- radiation
- nutrition
- infection and non-infectious disease
- stress
- drugs
Example of sperm defect: proximal droplet or free normal heads
Sperm: Steps in fertilization
Fertilization- Sperm
- Capacitation- occurs in uterine environment
- sperm cells gain ability to fertilize oocyte
- plasma membrane over Acromsome destabilized
- Acrosome Reaction- release of acrosomal encymes
- diges through zone pellucida
- sperm contacts oocyte!
- Fusion of sperm membrane with oocyte membrane
Ovum: Steps in fertilization (2)
Steps in fertilization-Ovum
Sperm Contact with oocyte plasma membrane
- causes relase of proteases from cortical granules
- modifies zone pellucida (becomes barrier to other sperm)
Ca++ wave causes oocyte to complete Meiosis II= 1N
Over all fertilization
Fertilization
Male Pronuclei + Female Pronuclei = Syngamy= ZYGOTE (2N)
at which point in spermatogenesis does it first become haploid?
spermatatid
what stage in follicular development is characterized by large fluid filled antrum and a cumulus oophorus?
tertiary follicle
in dog, what stage is released from ovary during ovulation?
primary oocyte
what stage implants in the wall of the uterus?
blastula
