Flashcards in Human Development Deck (89):
What happens when sperm and egg unite?
Form a zygote
How many sperm survive the trip to the egg?
A few thousand
How many sperm made during a lifetime?
How many sperm per ejaculate?
How many eggs at birth for Women?
How many eggs released during lifetime?
Do large or small animals have the largest sperm?
Small, it could be a matter of the resources they have available
How long does it take for sperm tail to develop?
How long does it take for sperm production?
What does the Sperm head contain?
Where is Mitochondira present in relation to sperm
Present in large amounts adjacent to the tail, synthesizes ATP
What is Acrosome?
Caps the head
What is a Centriole?
Enables first division of zygote to take place .
When will sperm mature?
Matures when it passes out of the testes, into the epididymis where secretions from the wall help them mature
Where is Sperm stored until needed?
In the last stretch of the epididymis until needed
Before ejaculation, sperm passes through what?
The vas deferns, the ejaculatory duct, and the urethra
What does Semen consist of?
Sperm and Secretions from accessory glands
What do Seminal Vesicles secrete?
Fructose (Nourishes Sperm) and Prostaglandins (Triggers contractions in the female tract thus aiding sperm movement)
Prostate Gland Secretions help to bufer the ___
acidity of the vagine. (pH 3.5-4). Fertility and Mobility is improved at pH 6
Bulbourethral Glands do what?
Secrete mucus-rich fluid into the urethra during arousal. This sperm mucus neutralizes any trace of acidity in urine left in the urethra
What doe a atypical ejaculation release?
40-350 million sperm
What does less than 20 million sperm during ejaculae mean?
Fertilization, Step 1
The sperm squeezes through cells left over from the follicle
Fertilization, Step 2
The sperm's acrosomal enzymes digest the jelly coat surrounding the egg
Fertilization, Step 3
The plasma membranes of the sperm and egg fuse
Fertilization, Step 4
The sperm nucleus enter the egg cytoplasm
Fertilization, Step 5
The sperm and egg chromosomes intermingle
What is induction?
One group of cells influences the development of an adjacent group of cells.
When does development of embryonic devlopment first begin?
What is Cleavage?
Series of rapid cell divisions that results in a multicellular ball
Cleavage continues as ____
the embryo moves down the oviduct toward the uterus
When does a Blastocyst first form?
After 6-7 days after fertilization
What does a Blastocyst consist of?
Consists of a fluid-filled hollow ball with about 100 cells and a small clump of inner cells called the inner cell mass which forms the fetus
What happens 9 days after conception?
Embryo undergoes gastrulation, an organized migration of cells
How many main things occur during the Gastrula stage?
Gastrula; Basic Body Plan #1
Ectoderm; Outer layer than forms the nervous system, skin, and retina
Gastrula; Basic Body Plan #2
Mesoderm; Middle layer that forms the heart, kidneys, muscles
Gastrula; Basic Body Plan #3
Endoderm; Lungs, Liver, the innermost layer that becomes the lining of the digestive tract
What is Programmed Cell Death?
Selectively kills cells to reshape the embryo and is used in formation of fingers and toes
What is Thalidomide used for?
Used for shrinking cancerous tumors before surgery
What is Thalidomide
Used for treating TB. Do not get pregnant while under treatment
What is DES?
Previously prescribed to prevent miscarriages. Granddaughters 40x greater chance of development lower genital tract clear-cell adoncarcinoma
What happens 8-9 Weeks After Fertilization?
Embryo is called a fetus. Has all organs an dbody parts. Limb buds have become tiny arms and legs
What is rapidly developing at 8-9 Weeks?
At 8-9 Weeks, what does SRY do?
Determines the maleness, is the determining gene. Codes for a protein involved in primary sex determination
What happens if SRY is present?
Embryo develops sperm producing testis
What happens if SRY is absent?
Gene called DAX1 produces an Anti-Testis factor (maleness inhibitor factor). Ovaries and eggs develop
Is secondary sex determination (breasts, hair, body type) determined by SRY?
No, it is determined by Hormones (Testosterone or Estrogen)
What happens at Week 10
Placenta is fully formed.
What is produced by the Placenta at 10 weeks?
Estrogen and Progesterone
At 10 weeks, do the mother's blood and fetal blood mix?
Mp. except for gases, viruses, drugs, drugs of abuse
What antibody can cross the placenta?
What is shown at 3-4 Months
Eyelashes, Eyebrows, Nipples
Increase in body length
Brain growth slow
Bone replaces cartilage
What is Week 12 known as?
The end of the First Trimester
When can the sex of the fetus be identified?
By the end of the First Trimester
How long does the Second Trimester Last?
At about 14 weeks, the fetus is
2.4 inches long and looks human
At 20 Weeks, the fetus is
7.6 inches long, weighs 1lb, and has the face of an infant
Fetus length at full term
Fetus weight at full term
What happens during Months 5-7
Lanugo (Body covered by "down")
White Cheesy Substance (Venix Caseosa)
12" and 3 lbs
When is the fetus able to survive outside the womb?
At 28 Weeks
The third trimister is a ..
Time of rapid growth and includes many important physical changes
At birth, a baby is
20 inches long and weights 6-8 pounds
What is Labor?
The birth of a child is brought about by a series of strong rhythmic contractions of the uterus
What is Oxytocins role in labor?
A powerful stimulant of the smooth muscle walls in the uterus, plays a key role in inducing labor
What is Prostaglandins role in Labor?
Induces labor. Contraction of Uterine smooth muscles and cervical ripening for the next 12-16 hours.
How many stages does Labor involve?
Labor; Step 1
Dilation; Longest, and opens cervix to 10cm.
What happens during Dilation?
Amniotic sac rptures. Explsion of mucus plug. Contractions become more intense and frequent
Labor; Step 2
Expulsion; results in the delivery of the child
Labor; Step 3
Delivery of the placenta; occurs within 15 minutes after the birth of the baby
Lactation; What do Estrogen and Progesterone contribute to?
The growth of mammary glands and ducts in the breast
During Lactation, wha tis secreted?
Lactation; After 1/2 days, what is produced?
Colostrum (Low fat, high IgA, anti-microbial factors) is produced
What does Oxytocin do during breastfeeding?
Forces breast tissues to contract and forces milk to the ducts
Oxytocin also forces...
uterine contractions so that the uterus can return to its normal size
If level of oxytocin is low,
the labor is intense. the cervix does not dilate. C-Section recommended.
the inability to have children after one year of trying
Due to underproduction or poor sperm quality. Can be because of smoking, or by impotence (erectile dysfunction)
Result from lack of eggs, failure to ovulate, or blocked oviducts
What is In Vitro Fertilization?
Begins with the administration of drugs that promote the development of multiple eggs
What is IVF followed by?
Surgical removal of eggs
Collection of Sperm
Fertilization of the eggs with sperm in Petri dish
Injection of the resulting embryos in a uterus
At around what age do females go through menopause?
Age 50, and its the cessation of ovulation and menstruation
How might menopause be adaptive?
Menopause might increase womens fitness by allowing her to invest more time and energy in her children and grandchilren instead of having more
Embryonic Stem Cells are ___
Totipotent; Can form all the cell types in the body.
Stem Cell Pros
Potential Cures for various things
Reduced Risk of Transplantation (Could possibly get copy of your own heart)
Stem Cell Cons
Destuction of Blastocyst
When does life begin
Should late fetuses be used for research
Temptation to clone humans?