ANA 205 Embryology Flashcards
What is human development?
Human development is a continuous process that begins when an oocyte (ovum) from a female is fertilized by a sperm (spermatozoon) from a male
Oocyte
refers to the female germ or sex cell produced in the ovaries
Sperm
refers to the male germ cell or male sex cell produced in the testes (testicles)
Zygote
This cell results from the union of an oocyte and a sperm during fertilization
Gestational age
Is the age of the embryo or fetus from the presumed first day of the last normal menstrual period
Embryo
The developing human during its early stages of development
How long is the embryonic period?
56 days (8th week)
Fetal period
begins on day 57 and ends when the fetus is completely outside the mother
At what stage is the developing human recognized as a fetus?
After the embryonic period (8 weeks) and until birth, the developing human is called a fetus
Sexual reproduction
occurs when female and male gametes (oocyte and spermatozoon, respectively) unite at fertilization
N number
refers to the amount of DNA in a cell
Ploidy
no. of chromosomes in a cell
What is meiosis
A cell division that takes place in the germ cells generate male and female gametes
What is gametogenesis?
Gametogenesis is the production of gametes from haploid precursor cells
Polar Body
A body formed from the uneven (asymmetrical) cell division of the oocyte
Interphase
Stage before mitosis
Includes G1 S and G2 phase
Undergoes growth and DNA is synthesized (S phase)
G1 Growth and protein synthesis
G2 Some cell organelles are duplicated
S phase is the longest phase
Cells that spend the majority of their life in G1 phase are called
Permanent cells
action of the fimbriae on the oocyte during oocyte transport
- sweeping action of the fimbriae
- fluid currents produced by the cilia of the mucosal cells of the fimbriae ; the secondary oocyte migrates into the funnel-shaped infundibulum of the uterine tube
Action of oocyte after reaching the infundibulum
From the infundibulum, the secondary oocyte passes into the ampulla of the tube, mainly as the result of peristalsis-movements (alternate contraction and relaxation) of the wall of the tube
Where are sperm produced?
Sperms are produced in the testes
Where are sperm temporarily stored?
Epididymis
What aids the movement of the sperm in the ductus deferens?
peristaltic contractions of the thick muscular coat of the ductus deferens
The male accessory sex glands and use
seminal glands (vesicles), prostate, and bulbourethral glands secrete fluid surrounding sperm
How many sperm are ejaculated into the vagina during intercourse?
200 to 600 million
What is the enzyme produced by the seminal gland whilst the sperm is in the cervical canal?
vesiculase
Function of vesiculase
coagulates(hardens) some of the semen or ejaculate and forms a vaginal plug (barrier) that may prevent the backflow of semen into the vagina
Function of prostaglandins in the semen
helps to stimulate uterine motility at the time of intercourse and assist in the movement of sperms to the site of fertilization in the ampulla of the tube
Which energy source is secreted by the seminal gland for the sperm in semen?
Frutose
What is the volume of sperm or ejaculate during intercourse?
averages 3.5 mL, with a range of 2 to 6 mL
Average speed of sperm
2 to 3 mm per minute, but the speed varies with the pH of the environment
At what stages is the sperm immotile and motile?
They are nonmotile during storage in the epididymis, but become motile in the ejaculate
Effect of pH on sperm speed
They move slowly in the acid environment of the vagina,
but move more rapidly in the alkaline environment of the uterus
What is capacitation?
The removal of the glycoprotein coat and seminal plasma proteins from the plasma membrane overlying the acrosomal region of the sperm
What is the zona pellucida?
The zona is a glycoprotein shell surrounding the egg that facilitates and maintains sperm binding and induces the acrosome reaction
What allows the sperm to penetrate the zona pellucida
Acrosomal enzyme, acrosin
What is the glycoprotein involved in the acrosomal reaction
zona glycoprotein (ZP3/ zona protein 3)
What happens when the sperm comes in contact with the oocyte during fertilization?
As soon as the head of a sperm comes in contact with the oocyte surface, the permeability of the zona pellucida changes
When a sperm comes in contact with the oocyte surface, lysosomal enzymes are released from cortical granules lining the plasma membrane of the oocyte
Function of lysosomal enzymes during fertilization
prevent sperm penetration and
inactivate binding sites for spermatozoa on the zona pellucida surface
Normal sperm count for males
100 million sperms per milliliter of semen in the ejaculate of normal males
Sperm count for a fertile male
20 million sperms per milliliter, or 50 million in the total semen
Sperm count for a sterile male
with fewer than 10 million sperms per milliliter of semen
For potential fertility, _____ of sperms should be motile after 2 hours and some should be motile after 24 hours
50%
Causes of male infertility
Male infertility may result from;
a low sperm count
poor sperm motility
medications and drugs
endocrine disorders
exposure to environmental pollutants
cigarette smoking
abnormal sperms
taking too much alcohol
or obstruction of a genital duct such as in the ductus deferens
What is a vasectomy
The most effective method of permanent contraception in the male is vasectomy, or excision of a segment of each ductus (vas) deferens
This surgical procedure is reversible in more than 50% of cases
Following vasectomy, there are no sperms in the semen or ejaculate, but the volume is the same
What is dispermy?
several sperms begin to penetrate the corona radiata and zona pellucida, usually only one sperm penetrates the oocyte and fertilizes it
Two sperms may participate in fertilization during an abnormal process known as dispermy, resulting in a zygote with an extra set of chromosomes
How long does capacitation last
7 hours
What is required for the sperm to bind to the zona pellucida
ZP3/ zona protein
Gonad
An organ that produces gamete e.g ovary and testes
Cytodifferentiation
The developer of specialized cells from unspecialized precursor cells
Which arm of a chromosome is longer
q arm
p arm is shorter