Reproductive system, final bio unit in highschool

Seminal vesicles: Provide fructose (energy for sperm) and prostaglandins (which send a chemical signal- like a hormone- to start muscle contractions in the female reproductive tract which helps push the sperm up to the egg. Additionally, these prostaglandins are what give females the feeling of pleasure. These prostaglandins act when the sperm is in the vagina.)


Prostate gland: produces an alakaline buffer as the vagina is very acidic- this helps the sperm to survive in this acidic enviornment.

Cowper's (bulbouretheral) glands: Mucus filled fluid, to protect sperm from acidic vagina, and assist swimming movement.)

These together all create semen which helps sperm get to the egg.

3-4 mL of semen (500 million sperm) are produced by the 3 glands.

Sperm are made for speed, being filled with many mitochondria, and have a limited energy reserve.

Head:

  Acrosome: a structure that caps the head of the sperm (filled with egg digesting enzymes that are needed because the eggs have a protective covering that need to be broken down before the sperm can fertilize it. Two sperms required- one to break the layer using its acrosome and one to fertilize.)

  Nucleus: contains DNA

Midpiece:

  Centrioles (leftovers from the process of meiosis) and mitochondria (needed for energy to make the sperm travel to the egg)

• Tail:  
•  Flagellum: Tail that propels

The sertoli cells nourish the developing sperm. They are in both the testes and in the epididymis.

Parasympathetic and somatic nervous response:

Erection: erectile tissue (spongiosum) fills with blood (veins and urethera compress which allows no blood to leave once it has entered. Additionally, this stops pee from entering as the sphincter at the base of the bladder closes.)

Sympathetic nervouse and somatic response:

Ejaculation: Semen (seminal/ejaculatory fluid) enters the urethra, pushed out by smooth muscle contractions.

A fluid composed of sperm and ejaculatory fluid (from the seminal vesicle, cowper's gland, and the prostate gland)

1. Testis: coiled seminiferous tubules (make sperm) and interstital/leydig cells (make testosterone) which house sertoli cells (nourish developing sperm, and produce inhibin.)

2. Epididymus: "sperm school"- this is where the sperm mature

3. Ductus/ vas deferens tubes: carries sperm from the testes to the inside of the body

4. Ejaculatory duct: Sperm mixes with ejaculatory fluid (from 1. seminal vesicle, 2. prostate gland, 3. cowper's gland)

5. Urethra: ejaculatory fluid (semen) leaves penis.

Testis: coiled seminiferous tubules (make sperm) and interstital/leydig cells (make testosterone) which house sertoli cells (nourish developing sperm, and produce inhibin.)

The scrotum is the sack containing the testes. The temperature is cooler in the testes (in the scrotum) as sperm develop and get stored in these temperatures.

Fertilization: Fusion of male and female sex cells, which produces a zygote. 

Zygote: A fused cell (fusion of male and female sex cells) that divides (using mitosis) many times to form a blastocyst --> embryo ---> fetus.

Females: The female gonads are ovaries, they produce progesterone and estrogen, they produce eggs, and their secondary sex characteristics include hair, fat at breasts and thighs, and increased senses. 

Males: The male gonads are the testes, males produce testosterone, their gonads produce sperm, and their secondary sex characteristics include hair, fat at the waist, muscle, and voice.

ovulation: Ovaries

fertilization: fallopian tube

implantation: uterus (endometrium)

Parturition: vagina

Female sexual maturity starts at puberty and ends at menopause.

Myometrium: muscular outer layer that pushes the baby out the birth canal. 

Endometrium: glandular inner lining that provides nourishment for the developing implanted embryo. 

Menstruation: if pregnancy does not occur, the endometrium layer and the egg are shed.

Cervix: a muscular band that dilates during birth. It seperates the uterus and the vagina.

Ovaries: hold and release eggs (ovum) + progesterone and estrogen production. Ovaries alternate each month producing 1 egg from the inside of a follicle (ovulation).

Oviducts (fallopian tubes): passageway for the ovum to move from the ovary to the uterus. Collect the egg (ova) at their fingerlike endings called the "fimbria"and transport it inside the tubes for fertilization. 

Uterus (womb): site of implantation of a fertilized ovum and where embryo, then fetus develops. 

Vagina (birth canal): The muscular canal extending from the uterus to the exterior of the body. Strongly acidic (to kill invaders).

Hormone:	Produced in:	Function:
Gonadotropic-releasing hormone (GnRH)	Hypothalamus	Activates the pituitary to release FSH and LH
Follicle stimulating hormone (FSH)	Anterior pituitary	stimulates the development of the follicle cells in the ovary
Lutenizing hormone (LH)	Anterior pituitary	Stimulates ovulation (spike in LH, plus estrogen and FSH) and causes the formation and maintenance of the corpus luteum.
Estrogen	Follicle cell (in the ovary)	secondary sex characteristics, thickening of the endometrium
Progesterone	Corpus luteum (in the ovary)	inhibits ovulation (because the mother is already pregnant), inhibits uterine contractions (to prevent baby from being birthed prematurely), and maintains endometrium
Inhibin	Granulosa cells (in the ovary)	Inhibits FSH production

At around 40 years of age, males experience a decline in testosterone levels. This can cause fatigue, depression, loss of muscle/bone mass, and the growth of the prostate gland (squeezes urethera, may be cancerous)

Hormone:	Produced in the:	Function:
Gonadotropic hormone (GnRH)	Hypothalamus	Stimulates secretion of FSH and LH
Follicle stimulating hormone (FSH)	Anterior pituitary	Production of sperm cells (in seminiferous tubules)
Lutenizing hormone (LH)	Anterior pituitary gland	promotes production of testosterone (androgens) in the testes in the interstitial cells
Testosterone and androgens	Interstitial cells (testes)	stimulates spermatogenesis, develops secondary sexual characteristics, and creates sex drive in men
Inhibin	Sertoli cells (testes)	inhibits FSH production in anterior pituitary

Sex is determined by hormones after the 7th week of fetal development. 

Ex. boy: y-chromosome carries gene for testis determining factor (TDF). This makes the ovaries drop out of the body cavity and form testicles.

Occasionally, the fertilized embryo can become implanted in a layer of underdeveloped endometrium in the oviduct (fallopian tube). This can lead to the death of the mother and the fetus.

• Flow phase (menses): days 1-5
• the corpus luteum has been degenrated since the end of the last cycle, causing progesterone and estrogen levels to drop heavily (no more hormones keeping the uterus maintained and stopping contractions). This causes shedding of the endometrium and the egg (menstruation) so that new ones can be produced next month. 

• Follicular phase (proliferative phase): days 6-13
• In this phase, the follicles in the ovary start to develop. This produces estrogen and the endometrium thickens due to the estrogen.

• Ovulation: day 14
• the egg bursts from the ovary and the follicular cells turn into the corpus luteum. 

• Secretory phase: 15-28
• oocyte leaves ovary, Estrogen levels decline (even if the corpus luteum makes some, it is not as much as the follicle did in the proliferative phase). Additionally, the corpus luteum forms which produces progesterone which maintains the endometrium.

Once ovulation has occured, the remaining follicle in the ovary turns into the corpus luteum which secretes progesterone (and estrogen). This increased amount of progesterone and estrogen causes a negative feedback loop to the anterior pituitary gland, causing decreased amounts of FSH and LH to be secreted. This decreased amount of LH causes the corpus luteum to degenerate into the corpus albicans which further lowers estrogen and progesterone. The decreased estrogen and progesterone causes the anterior pituitary gland to start releasing FSH again and the cycle beings again. The breaking down of the corpus luteum only happens if the egg is not fertilized. If it is, the fetus releases human chorionic gonadotropin (hCG) which keeps the progesterone and estrogen at high levels and no FSH is made. The cycle stops during pregnancy.

Gonadotropic releasing hormone (GnRH) causes the anterior pituitary gland to release FSH which causes the follicle in the ovaries to develop. This follicle releases estrogen (for secondary sex traits, and thickening of the endometrium). This Estrogen causes GnRH to be released from the hypothalamus (positive feedback loop- endproduct causes the loop to happen more). This increased GnRH causes LH to be released (from anterior pituitary). This surge in LH causes ovulation (egg released from follicle and ovary).

28 days

trophoblast: chorionic layer

Inner cell mass: embryo

When the baby leaves the mother feet first, not head first.

the placenta is a part in the uterus that is richly supplied with blood. Veins are sent to the baby, through the umbilical cord (is what links the baby and the mother), to supply it with nutrients and oxygen and arteries are sent from the baby, through the umbilical cord, to the mother to remove wastes. (think of it from the baby's perspective, arteries= away from baby,veins= back to baby). 

To absorb the nutrients, finger like projections called the chorionic villi, ensure the fetus gets what it needs. 

Progesterone and estrogen.

Chorion (chorionic layer): outer layer- produces HCG. Forms from the trophoblast of the blastocyst. 

Amnion: inner layer that develops into a fluid filled sac. It insulates the embryo/fetus and it protects the embryo from infection, dehydration, impact, and temperature change. 

Allantois: later develops into the umbilical cord

Yolk sac: initial food for embryo before umbilical chord sets up (vestigial)

Neuralation: from ectoderm: Tissues fold over which forms a neural tube which then forms the brain and spinal chord. Organ formation begins. Folic acid (amino acid), is essential for neural tube development. 

Gastrulation: from endoderm: formation of gastric digestive tubing. And the rest of the body.

The embryonic disk inside the embryo (gastrula) forms a 3 layered embryo; morphogenesis.

Ectoderm: (outer) --> skin, eyes, nervous system, pituitary gland

Mesoderm: (middle) --> muslces, bones, inner skin, blood and lymph vessles, heart, kidneys, spleen....

Endoderm: (inner): digestive tract, bladder, liver, gallbladder, pancreas, thymus, thyroid gland, lungs

There are 3, three month periods of development. These are called the prenatal trimesters. This means that overall, pregnancy lasts for 9 months. 

Month 1-8 (embryonic development): mom support structures form and embryo tissues/organs form. 

Month 9 untill birth (fetal development): Organs function which forms body systems and the body grows rapidly.

There are high levels of progesterone and estrogen (produced by the corpus luteum) which has a negative feedback effect on the gonadotropic hormones (FSH and LH). This keeps the uterus from shedding the endometrium, inhibits uterine contractions to prevent premature birth, and prevents ovulation.

HCG (human chorionic gonadotropic hormone) is a placental hormone that maintains the corpus luteum for the 1st 3 months, allowing for progesterone and estrogen production. Afterwards, HCG production slows down, the corpus luteum breaks down, and estrogen and progesterone are produced by the placenta itself. (cells of embryo and endometrium fused)

Fraternal (dizygote) twins: Occasionally, two eggs are released and fertilized at the same time by two different sperm cells. 

Identical (monozygotic) twins: results when a single fertilized egg splits into two cell masses. (one cell breaks off during mitosis and starts to form a different zygote with the same genetic information.)

4-6 days after fertilization/conception, as the zygote is travelling down the fallopian tube to the endometrium, it divides (mitosis) repeatedly (cleavage) to form a morula (16 cells). the morula divides; forming a blastocyst. Eventually, the blastocyst attaches to the wall of the uterus (endometrium). This is called implantation.

Tubal ligation: tying off oviduct. Cutting apart the oviduct and putting it back together so that sperm cannot reach egg.

Vasectomy: cutting vas deferens so no sperm can get into the body and leave

contraceptives: pill, injection, implants of fake progesterone (stops FSH and LH production and egg release)

Physical and chemical barriers: condoms, diaphragm, spermicides, IUD.

Natural family planning (the rythm method)- no sex when a women is fertile.

Surrogate mother: woman carries the baby for a couple. 

Super-ovulation: Hormones that cause multiple eggs to be released

Artifical insemination: When sperm is collected (sperm bank) and concentrated before being placed into the vagina by a catheter

In vitro fertilization: Egg is fertilized outside of female body. Basically, the eggs are removed from the mother and sperm are removed from the father. Then, fertilization occurs in a petri dish then the zygote is incubated. Once a blastocyst has formed. They can return it to the mother's womb where implantation can occur. Sometimes multiple eggs are taken from the mother and then the parents are able to choose which blastocyst they want after the genes of each baby has been told to them.

Males: blockage of the vas deferens, low sperm count or abnormal sperm due to: overheated testicles (sperm need cool conditions to form), smoking, alcohol, toxic chemicals, and radiation. Additionally impotency, the inability to become erect, can cause infertility. This can be caused because of stress, disease, or because of a nerve/hormone problem. 

Females: Blockage of oviducts, no ovulation (hormonal imbalance, malnourishment), endometriosis (endometrium grows outside uterus), or damaged eggs (exposure to toxic chemicals, or radiation.)

When the baby starts suckling, it stimulates the hypothalamus to release oxytociin through the posterior pituitary gland. Oxytocing then binds with the mammary muscles and causes the release of milk. The baby begins to suckle more to drink the milk which causes the release of more oxytocin and more milk and more suckling and the cycle keeps going untill the baby is full.

Colstrium (pre-milk) is full of proteins, antibodies, but has less fat so it is not white. This is what comes before the mother begins to make actual milk (when she uses the fats in her body for the milk).

Increased progesterone and estrogen levels from the placenta cause the breast to prepare for milk production. Prolactin is a hormone from pituitary gland responsible for milk production in the breast. Oxytocin, which is stimulated by the suckling action of the baby (which is a reflex) and by the crying of the baby, causes smooth muscle contractions, forcing milk into the ducts and allowing for the release of milk. Oxytocin can help bring the uterus back to it's original size before pregnancy.

As the baby wants to come out, it's head pushing against the cervix causes the release of oxytocin from the pituitary gland. Estrogen induces oxytocin receptors on the uterus, which allows this oxytocin to bind to the uterus and cause contractions. Oxytocin can also stimulate the placenta to make prostaglandins which stimulate more uterus contractions. Now that these contractions are occuring, the baby is pushing harder against the cervix. This causes the same look to occur and contractions occur once again, creating a continual loop untill the baby has been birthed.

-The woman's water breaks (amniotic membrane bursts releasing fluid)

-Relaxin, a hormone (prostaglandin) produced in the placenta prior to labour, causes ligaments within the pelvis to loosen. 

-There is also a decrease in progesterone production

Dilation stage, Expulsion stage, and the placental stage

Dilation stage: The cervix thins and dilates. Additionally, before going into labour, Relaxin, a hormone produced in the placenta (prostaglandin) causes the ligaments within the pelvis to loosen. 

Expulsion stage: Uterine contractions cause the delivery of the infant. 

Placental stage: delivery of the placenta.

Teratogens are harmful substances ingested/inhlaed by the mother which can be harmful to normal development. Especialy in the 1st 8 weeks, because that is when the most important parts of the body are being formed such as the heart.

Examples:

Smoking: lack of O2, premature birth, stillborns, miscarriages

Alcohol: may bring down the weight, height, and mental ability of the baby. May also cause fetal alcohol spectrum disorder (FASD)

Drugs: various effects

Other examples: Radiation and pollution

• -Infant is around 530mm and weights 3400g or 3.4kg
• -Baby grows rapidly and turns upside down
• -Organs further develop

• -57 mm fetus 
• -All organs have formed
• -Soft hair covers body
• - eyelids and eyelashes formed

• -Embryo is 7mm (500x larger than the egg)
• -4 chambered heart has formed
• -Anterior brain formed
• -Limb buds have formed (w/ tiny fingers and toes)
• -sucking reflex evident

Sexual reproduction is defined as the fusion of male and femalse sex cells. Species surivival is dependent on producing numerous and varied offspring.