A&P II Chapter 10: Reproductive System

gametogenesis

the process in which cells go through meiosis to make gametes

spermatogenesis

in males; starts with a primary spermatocyte in Meiosis 1 and produces two secondary spermatocytes. In Meiosis two, 4 spermatids are produced

oogenesis

in females; begins before female infant is born and then is suspended until puberty. once reactivated it continues until it ceases around 45-55 years old. Occurs once a month as part of ovarian cycle. Meiosis 1 starts with a primary oocyte which produces a secondary oocyte and a polar body (the secondary oocyte is the only one that can give rise to an egg and the polar body will degenerate). In Meiosis 2, the secondary oocyte produces a mature egg (ovum) and another polar body. The polar bodies cannot be fertilized

haploid cells

have one copy of every gene, meaning a single set of chromosomes. They are produced by meiosis with 23 chromosomes and are gametes. 

diploid cells

have two sets of chromosomes. They are produced by mitosis with 46 chromosomes and are our body cells.

homologous chromosome

pairs of chromosomes (one from mom and one from dad) that have the same genes but may have different alleles (think eye color where mom could give blue and dad could give brown)

sister chromatids

two identical copies of a single chromosome that are joined at the centromere

steps of meiosis

• Meiosis 1 – this is taking a single diploid cell and turning it into 2 haploid cells (no longer homologous chromosomes XX) 

  • Prophase 1 – X start to condense down and homologous chromosomes find their pair, sometimes the innermost sister chromatids cross over and the DNA switches (Crossing over) to make the sister chromatids genetically different 

  • Metaphase 1 – X line up in middle of cell and the pairs line up next to each with mom on one side of equator and dad on the other but it doesn't matter which side is which so mom & dad could be mixed on both sides or not. So hypothetically speaking some cells could only contain dad's information but is not super likely 

  • Anaphase 1 – the two pairs are pulled apart by mitotic spindle 

  • Telophase 1 – pairs are separated and are at the poles, each chromosome is still in its replicated form 

• Meiosis 2 – this is the same as mitosis with half as many chromosomes 

  • Prophase 2 – X are condensed 

  • Metaphase 2 – X line up in the middle and mitotic spindle attaches 

  • Anaphase 2 – sister chromatids are pulled apart to the poles 

  • Telophase 2 – undergoing cytokinesis to split the cytoplasm so you end up with 4 genetically different cells 

independent assortment

It is the random separation of homologous chromosomes during meiosis meaning that inheriting one trait does not influence the inheritance of another trait which creates a variety of possible genetic combinations in offspring; it occurs during Metaphase 1 

crossing over

It is the exchange of genetic material between homologous chromosomes to create new combinations of genes ("patchwork chromosomes"). It occurs during Prophase 1 

outcomes of independent assortment & crossing over

It increases genetic diversity by creating new combinations of genes and genetically unique gametes. Crossing over exchanges genetic material between homologous chromosomes which creates new allele combinations on each chromosome. Independent assortment then randomly shuffles these chromosomes so each gamete ends up with a unique combination of the original parental chromosomes 

primary sex organ and function in males

Testes – function is to make sperm, also produce testosterone which is responsible for male reproductive structures and characteristics 

primary sex organ and function in females

Ovaries – produce eggs (ova) for potential fertilization, also produce hormones like estrogen and progesterone which regulate the menstrual cycle and are responsible for development and function of reproductive organs 

accessory organs in males

seminal vesicles, prostate, bulbourethral glands, vas deferens, penis 

accessory organs in females

uterus, oviducts, mammary glands, vagina, uterine tubes 

gonadotropin-releasing hormone

released from the hypothalamus at puberty, It triggers the pituitary gland to release follicle stimulating hormone and luteinizing hormone that then stimulate the release of sex hormones (testosterone, estrogen and progesterone) to regulate gametogenesis.

the testes are housed:

in the scrotum which is a pouch of skin that hangs outside the body cavity 

plexus of veins found in the spermatic cord

• To create a heat exchange system – the cool venous blood absorbs heat from the warmer arterial blood which lowers the temperature of the blood entering the testes so that they stay at a slightly lower temperature than the body to create proper sperm production. Also collects blood from the testes and epididymis. 

• There is a single testicular artery to give blood to the testes, blood also needs to be returned and it comes through the venous plexus which is a network of veins 

• It is innervated meaning there are nerves and pain receptors and thermoreceptors 

seminiferous tubules

They are coiled tubes within the testes that are where spermatogenesis takes place. Function is to generate mature sperm cells and leydid cells involved in hormonal regulation.  

duct system that transfers sperm from seminiferous tubules to epididymis

Seminiferous tubules merge into a single tube called rete testis which is a network of tubes that transports sperm to the efferent ductules that carry sperm to the epidiymis 

epididymis

It is where sperm is stored and is where sperm fully mature. It is split into three parts (head, body & tail) and the sperm leave through the tail region at the vas deferens. Nonmotor microvilli (stereocilia) are here that absorb excess testicular fluid and provide nutrients to the sperm 

vas deferens

A tube that transports sperm from the epididymis to the urethra where they are expelled during ejaculation. Has muscular contractions to propel the sperm forward 

cell types found in seminiferous tubules

There are spermatogenic cells (the sperm-producing cells) and sustentacular cells (they support sperm production, nourish the sperm cells, produce inhibin to stop sperm production when sperm count is too high, etc.) 

cell types found outside seminiferous tubules

Leydig cells are found outside the tubules and they produce testosterone. The process is stimulated by luteinizing hormone. Myoid cells are also found in the walls of seminiferous tubules to help transport sperm

FSH and LH in males

The anterior pituitary gland produces these. FSH (follicle stimulating hormone) stimulates cells in the testes to support sperm production and the LH (luteinizing hormone) stimulates leydig cells to produce testosterone. 

seminal fluid

produced by the seminal vesicles, prostate gland and bulbourethral glands. The function is to nourish the sperm, transport them and help them survive, protects them from the acidic environment of the female, and move through the female reproductive tract 

structures within the penis allowing for erection

• The corpora cavernosa are the two cylinder shapes that run along the top of the penis that fill with blood and cause it to become stiff 

• The corpus spongiosum runs along the bottom of the penis and becomes slightly engorged 

4 parts of the uterine tubes

• Isthmus – constricted portion of the uterus that connects body of uterus to the cervix (lower part) 

• Ampulla – widest part of the fallopian tube 

• Infundibulum – funnel shaped opening closest to the ovary at the end of the fallopian tube which connects to the uterus 

• Fimbria – hair like ciliated projections to make sure egg finds its way into fallopian tube 

3 parts of the uterus

Composed of three regions: the body (main region), fundus (rounded region superior to entrance to uterine tubes) and cervix (narrow neck) 

function of ovaries

produce the oocyte (egg) and hormones (estrogen, inhibin, relaxin) 

function of uterine tubes

the pathway for eggs to travel from the ovaries to the uterus and where fertilization occurs 

function of the uterus

The egg moves to the uterus where it plants itself in a healthy pregnancy. Technically not pregnant until the implantation happens. It also expels the baby in childbirth with the muscular wall 

follicle

Small and protective sac or pouch-like cavity in the body that can contain an egg. Ovarian follicles are fluid-filled sacs in the ovaries that each contain an immature egg and release a mature egg during ovulation

polar bodies

Small and non-functional cells that form during oogenesis. They typically degenerate 

what causes menopause

A woman's ovaries no longer producing sufficient amounts of estrogen and progesterone 

FSH and LH in females

• Luteinizing hormone which triggers ovulation (release of an egg from the ovary) 

• Follicle stimulating hormone stimulates growth and development of multiple follicles in the ovaries 

• They are released in response to gonad releasing hormone being triggered from the hypothalamus

progesterone in females

Progesterone is a steroid hormone that thickens the lining of the uterus and regulates ovulation by preventing release of additional eggs; produced by the corpus luteum after ovulation

HCG in females

Human chorionic gonadotropin which is produced by the placenta in pregnancy. It maintains the corpus luteum (temporary gland producing progesterone), supports fetal grown and detects pregnancy in urine or blood tests 

site of ovulation

mature egg is released from its follicle in one of the ovaries and then travels to the fallopian tube

site of fertilization

fallopian tube

site of implantation

uterine lining

site of embryogenesis

uterus

difference between sex & gender

Sex is the classification based on biological characteristics (hormones, chromosomes, reproductive organs) while gender is a social construct referring to a person's internal sense of identity 

difference between genetic and phenotypic sex

Genetic is determined by sex chromosomes (XX and XY) while phenotypic sex is based on physical characteristics like internal & external genitalia 

intersexed condition

When the genotype and gonad development doesn't match their external genitalia – there are people who think they are one sex but are actually not because of the genes 

aneuploidy of the sex chromosomes

When chromosomes don't separate as they should (X, XXX, XXY, XYY); can result in developmental disabilities, infertility  

types of birth control

• Behavioral methods – abstinence, rhythm method, withdrawal 

• Barrier methods – prevent sperm from moving beyond vagina 

• Hormonal methods – oral contraceptives injecting estrogen to prevent ovulation 

• Intrauterine methods – IUD to prevent pregnancy by preventing implantation of fertilized ovum into uterine wall as the copper device is poison 

• Permanent methods – vasectomy in male (taking the vas deferens and ligating or cauterizing it) or tubal ligation for women to ligate or cauterize ends of uterine tubes  

inftertility

slightly more common in femails; In males, 40% of cases are caused by this, usually due to low sperm count (if count falls below 15 million per ml of semen).  

issues in females that can cause infertility

• Problem with ovulation (without ovulation there is no secondary oocyte to fertilize) 

• Issues with transfer of oocyte from the ovaries or issues with implantation, things like blockage of uterine tubes, stress, overweight or underweight, alcohol, endometriosis 

causes of erectile dysfunction

Cardiovascular disease, diabetes, obesity, low testosterone, nerve damage, smoking, alcohol, pelvic trauma, psychological, medications, age 

screenings for prostate cancer

Blood test to measure amount of prostate specific antigen and an exam to feel for any abnormalities on the prostate gland 

STI that often leads to cervical cancer

HPV which causes abnormal cervical cells to develop into cancer over time 

all human cells except for gametes are diploid

diploid cells have two copies of every chromosome; we really have 23 pairs of chromosomes to total 45 (23 from mom and 23 from dad) - 22 pairs are autosomes and 1 pair is the sex chromosome (XX or XY)

spermiogenesis

sperm maturation, cell of the sperm gets longer and sheds excess cytoplasm, develops organelle structure on head (acrosome) and increases mitochondria as it needs tons of energy to swim; process takes about 60-70 days

ligaments holding the ovaries in place

these stretch in pregnancy to create discomfort

• Broad ligament - largest, attaches ovaries to uterine tubes and uterus 

• Ovarian ligament - connects medial surface of ovary to uterus 

• Suspensory ligament - connects lateral surface ovary to pelvic wall 

location of all femal reproductive organs

abdominopelvic cavity

uterine wall layers

• Perimetirum - outermost serous layer  

• Myometrium - middle layer made of smooth muscle 

• Endometrium - innermost layer 

tunics of the vagina

• Inner mucosa - stratified squamous epithelium 

• Middle muscularis - smooth muscle 

• Outer adventitia - connective tissue 

Ovarian and uterine cycle

Monthly sequence of events controlled by hormones and lasts 28 days, has 3 phases, uterine lining gets thick after the period and then we shed the uterine lining which then causes the period to start again 

• Follicular phase - increased estrogen 

• Ovulation - egg is released 

• Luteal phase - when secondary oocyte is released 

what happens if fertilization occurs

• Pre embryo or fertilized egg starts secreting human choronic gonadotropic (HCG) which mimics leutenizing hormone 

• After about 3 months the placenta of the developing fetus produces its own progesterone and estrogen and the corpus luteum can regress into a corpus albicans 

• If the pre-embryo is producing HCG you can get a false positive if it doesn’t implant