Gametogenesis Flashcards
What are the functions of the ovaries?
Produce ova
Secrete estrogen and progesterone which are responsible for the development of the secondary sexual characters and regulation of pregnancy
What are the components of the uterine tube?
Infundibulum (pick the ova), ampulla (site of fertilization), isthmus and interstitial part
What are the layers of the uterus?
External to internal:
1. Perimetrium - purple
2. Myometrium - green
3. Endometrium - blue
What is the perimetrium?
External covering of peritoneum
Myometrium
Thick smooth muscle layer
Endometrium
Internal lining of mucosal layer
Layers of the endometrium?
Basal layer
Functional layer
Functions of the basal layer
Contains the ends of the uterine glands
Doesn’t shed during menstruation
Regenerates the functional layer
Functions of the functional layer
Disintegrates & sheds at menstruation and after delivery
What is gametogenesis?
Process of formation sperms (spermatogenesis) in males or ova (oogenesis) in females
What is spermatogenesis?
Definition: Transformation of spermatogonia into sperm
Site: Occurs in seminiferous tubules of testis
Onset: Begins at puberty and continues throughout life
How long does spermatogenesis take to occur?
60 days in seminiferous tubules
How long do sperm last in female genital tract?
48 hours
What is 1 and its function?
Testis
Produce sperm and secrete testosterone
What is 2 and its function?
Epididymis
Stores the sperm
What is 3 and its function?
Vas deferens
Transports the sperm before ejaculation
What are 4 and 6 and their functions?
4 = Seminal vesicle
6 = Prostate
Secrete seminal alkaline fluid that nourishes sperm
What is 5 and its function?
Ejaculatory duct
Transfer the sperm into urethra
What is 7 and its function?
Bulbourethral glands
Secrete clear fluid that washes the urethra just before ejaculation
What are the stages of spermatogenesis?
4 stages of spermatogenesis:
1. Proliferation
2. Growth
3. Maturation
4. Transformation
What is proliferation (spermatogenesis)?
Increase in number of spermatogonia
Spermatogonia (44 + XY) divide by mitosis into daughter spermatogonia which also contain (44 +XY)
What is growth (spermatogenesis)?
Increase size of spermatogonia
The daughter spermatogonia enlarge to form primary spermatocytes, which have (44 + XY)
Stages of maturation phase (spermatogenesis)
First maturation division
Second maturation division
First maturation division (spermatogenesis)
Each primary spermatocyte produces 2 secondary spermatocytes, each contains (22 + X OR 22 + Y) of double stranded chromosomes
Second maturation division (spermatogenesis)
Each secondary spermatocyte produces 2 spermatids, each contains (22 + X OR 22 + Y) of single stranded chromosomes
What is transformation (spermatogenesis)?
Spermatids transformed to mature sperm
1. Nucleus condenses
2. Acrosome (sac of enzymes) forms
3. Most of the cytoplasm is shed
4. Flagellum appears
What are the parts of the mature sperm?
Head composed of:
* Nucleus
* Acrosomal cap: Enzymes that facilitate penetration of secondary oocyte
Neck: Junction between head and tail
Tail: Responsible for motility. Composed of:
* Middle piece: Contains mitochondria
* Principal piece
* End piece
Normal sperm count
Volume of ejaculate = 2-6 ml
Ejaculate contains 200-600 million sperm
~100 million sperm/ml
What makes up the ejaculate?
Sperm = 5%
Secretions from seminal glands = 60%
Secretions from the prostate = 30%
How do sperm move through the female reproductive system?
Slowly in acidic vaginal environment
Rapidly in alkaline uterine environment
~200 sperm reach fertilization site
Most sperm degenrate during passage through female genital tract
What is azoospermia?
Absence of living sperms in the semen
What is oligospermia?
<10 million sperm/ml = sterile
Immotile & abnormal shaped sperms may cause oligospermia
How many sperm should be motile for potential fertility?
At least 40% of sperm should be motile after 2 hours for potential fertility
What is a vasectomy?
Trans-scrotal incision of vas deferens
Most effective method of male contraception
No sperms in the ejaculate, but seminal fluid vole is the same as before
What is oogenesis?
Definition: Transformation of oogonia into oocytes
Site: Occurs in the ovaries
Onset: Starts during the fetal period. Reactivated at puberty. Continues until menopause (45-55 years)
What are the stages of oogenesis?
Prenatal events
1. Proliferation
2. Growth
3. Maturation: First maturation division
Postnatal events
1. Maturation: Completion of first maturation division
2. Maturation: Second maturation division
What is proliferation (oogenesis)?
Oogonia proliferate by mitosis forming daughter oogonia (44 + XX)
What is growth (oogenesis)?
Daughter oogonia enlarge to form primary oocytes (44 + XX)
First maturation division (prenatal oogenesis)
Primary oocyte go through interphase & prophase
At birth, all primary oocytes have completed preparation for first meiotic division
They remain in prophase 1 until puberty
First maturation division (postnatal ooegenesis)
Occurs at puberty
~Once every month in either ovary
Cytoplasmic division is unequal (large amount in secondary oocyte)
Each primary oocyte gives rise secondary oocyte & 1st polar body (22 + X) each
First maturation division (postnatal oogenesis)
Occurs at puberty
~Once every month in either ovary
Cytoplasmic division is unequal (large amount in secondary oocyte)
Each primary oocyte gives rise secondary oocyte & 1st polar body (22 + X) each
Polar body is discarded
If the first polar body doesn’t degenerate, it divides into 2 polar bodies each of them has (22 + X)
Second maturation division (oogenesis)
Occurs in the uterine tube if fertilization occurs
The 2ry oocyte produces
* Mature ovum (22 + X) = fertilized 2ry oocyte
* 2nd polar body (22 + X)
Layers of the secondary oocyte
Zona pellucida: Non cellular covering of glycoprotein
Corona radiata: Layer of follicular cells
Peri-vitelline space (blue region): Space between zona pellucida & oocyte (red region) cell membrane
What are the potential results of non-disjunction during meiosis II?
Three possible abnormal gametes
Cell without any chromosomes is not considered a gamete
