Module 5 Flashcards
Why is sexual reproduction important?
- produces offspring that are genetically different to their parents
- generates variation within population
How is sexual reproduction expensive for animals?
- production of gametes
- production of pheromones
- cost of finding a mate
- competition b/w males
sex determination
- embryonic gonads form that could either become testes or ovaries
- the presence or absence of SRY gene decides which developmental pathway is followed
- this gene codes for TDF (a gene regulation protein)
- by binding to specific DNA sites, TDF stimulates the expression of genes for testis development
- found on Y chromosome
The gonads (testes & ovaries) produce which 3 major steroid sex hormones?
- androgens (principally testosterone)
- oestrogens (principally oestradiol)
- progesterone
- cholesterol is their precursor
primary sex characteristics
reproductive structures that develop in the embryo
- penis, testes, seminal vesicles, associated ducts
- ovaries, fallopian tubes uterus, vagina
- brain sex
ovaries
eggs mature in & are released by the ovaries (produces eggs, estrogen, & progesterone)
oviducts
collects eggs at ovulation, provides a site for fertilization then moves the embryo to the uterus
uterus
provides protection, food, oxygen and removal of waste products for the fetus during pregnancy
- blastocyst implants in the ENDOMETRIUM of the uterus
cervix
neck of the uterus which protects the fetus during pregnancy and then dilates to provide a birth canal
vagina
stimulates penis to cause ejaculation & provides a birth canal
What is folliculogenesis
development of the follicle (follicle includes egg, fluid accumulation, theca cells, granulosa cells)
Oogenesis
- mitosis - oogonium
- growth –> primary oocytes
- primary oocyte & its surrounding cells = follicle
- meiosis I - stops at prophase I –> primary follicle
- at menstrual cycle, meiosis I is finished –> large secondary oocyte + unequal division of cytoplasm (2 haploid nuclei)
- meiosis II –> stops in prophase II
- ovulation = follicle ruptures, releasing oocyte
- the remaining follicle cells form the corpus luteum, which produces progesterone + estrogen
- after FERTILIZATION, secondary oocyte completes 2nd division of meiosis to form an ovum (one set of chromosomes - haploid)
estrogen
- produces by granulosa cells in follicle
- acts via estrogen receptors
- regulates oviduct (Fallopian tube), uterus, cervix, vagina, & other sex organs
- prepares endometrium for implantation (increases vascularization, blood supply)
- promotes oestrus (or mating) behaviour
progesterone
- produced by corpus luteum
- acts via progesterone receptors
- regulates oviduct, uterus, cervix, vagina, & other sex hormones
- prepares endometrium for implanation
- modulates effects of estrogen, STOPS follicle growth
Menstruation
- elimination of the thickened lining of the uterus (endometrium) from the body via the vagina
- menstrual fluid: consists of blood, lining of the uterus, & uterine mucus
Hypothalamo-pituitary-gonadal axis (HPG axis)
- hypothalamus secretes gonadotropin releasing hormone (GnRH) that acts on anterior pituitary
- GnRH release is in pulses
- anterior pituitary produces gonadotrophins (FSHH & LH)
LH - luteinizing hormone
- stimulates theca cells to produce androgens
- a surge in LH stimulates ovulation
- stimulates formation of corpus luteum
what are theca cells?
Theca cells are a group of endocrine cells in the ovary made up of connective tissue surrounding the follicle. They have many diverse functions, including promoting folliculogenesis and recruitment of a single follicle during ovulation.
FSH - follicle stimulating hormone
- stimulates folliculogenesis
- acts on granulosa cells to stimulate the conversion of androgens to estrogens
what are granulosa cells?
Granulosa cells are a type of cell in your ovaries that produce hormones including estrogen and progesterone. Hormones released from the base of your brain (anterior pituitary) control the numbers and function of granulosa cells
When is the follicular phase?
days 1 - 14 (maturation of follicle)
when is the luteal phase?
days 14 - 28 (preparation for implantation)
What is endometriosis?
- affects 10% of women
- endometrial cells grow in other PARTS of body (eg around ovaries, bladder, rectum)
- severe abdominal pain & infertility
- endometrial cells have estrogen & progesterone receptors
What will happen to this endometrial tissue (outside endometrium) during the menstrual cycle?
- In response to hormones in the menstrual cycle the endometrial cells outside the uterus GROW in response to progesterone
- Shed into the pelvic cavity when the progesterone levels drop
Stages of menstrual cycle from day 1
- menstruation
- follicular phase
- ovulation
- luteal phase
where is sperm produced?
in the seminiferous tubules in the testis
Where is sperm stored?
in the epididymis
Van deferens
transports sperm from epididymis to urethra (via ejaculatory ducts)
seminiferous tubules
sperm with flagella are released in the lumen of the seminiferous tubules
occurs from outside to inside
testis
- sperm production –> controlled by Sertoli cells which convert testosterone to oestradiol to facilitate spermatogenesis
- hormone production –> testosterone is produced in Leydig cells (interstitial space in bw tubules) – steroid, androgen
How is testosterone produced?
- produced by Leydig cells
- steroid hormone
- acts via androgen receptor in cells
- can be converted to oestradiol in Sertoli cells to aid spermatogenesis
- modulates secondary sex characteristics in males
urethra
transfers semen during ejaculation & urine during urination
scrotum
holds testes at lower than core body temp
prostate gland
secretes alkaline fluid that is added to sperm at the start of ejaculation & helps sperm to swim
seminal vesicle
secretes an alkaline fluid at the end of ejaculation containing proteins that make the semen sticky
structure of mature sperm
specialized for motility w/ 3 parts
- head - acrosome containing enzymes to digest the eggs’ outer coating
- mid-piece - lots of mitochondria to power the journey through female reproductive tract
- tail (flagella) – 9+2 microtubule arrangement
stages in spermatogenesis
- outer layer called germinal epithelium cells (2n) divide by mitosis (spermatogonia)
- diploid cells grow –> primary spermatocytes
- 1st division of meiosis –> secondary spermatocytes (n)
- 2nd division of meiosis –> 2 spermatids (n)
- spermatids become associated w Sertoli cells which help spermatids –> spermatozoa (CELL DIFFERENTIATION)
- sperm detach from Sertoli cells & carried out of testis by fluid in center of seminiferous tubule
Which factors affect quality of male sperm?
- diet
- smoking
- drugs
- BMI
- alcohol consumption
- exposure to heat
- acute viral illness
HPG axis in males
- GnRH from hypothalamus stimulates release of LH + FSH from anterior pituitary
- LH stimulates Leydig cells to produce testosterone
- FSH stimulates spermatogenesis by acting on Sertoli cells
- testosterone affects accessory sex organs & secondary sex characteristics
- NEGATIVE FEEDBACK regulates testosterone + spermatogenesis
testosterone INHIBITS GnRH & LH secretion
inhibin produced by Sertoli cells INHIBITS FSH secretion
Which hormone is produced from fertilization?
hCG
stimulates corpus luteum to continue producing progesterone + estrogen
pregnancy kits detect hCG
contraceptive methods
- physical barriers (condoms, diaphragm, etc.)
- chemical (oral contraceptive pill, contraceptive implants)
How does the oral contraceptive pill work?
- combined oral contraceptive contains synthetic progesterone + estrogen
- works by suppressing GnRH, FSH, & LH
- prevents follicle growth & ovulation
- increases cervical mucus thickness to stop sperm
- continual exposure to progesterone & estrogen THINGS endometrial lining, hampers implantation
which endocrine disruptors can affect reproductive organs?
- hormonally active synthetic chemicals
- plastics, pesticides, phthalates
Bisphenol A (BPA)
- is a monomer
- leaches from plastics when heated, or they age, or treated w/ acid & base
- oestrogen mimics, binds to estrogen receptors
Key features of exchange surfaces
- large surface area relative to volume
- very thin barrier
- concentration gradient
- selectively permeable
Fick’s law
rate of diffusion = (SA x partial pressure gradient x diffusion coefficient)/diffusion distance
why is air a better respiratory medium than water?
water is much denser than air so much more energy is needed to move water around
O2 has low solubility in water; CO2 had higher partial pressure in water
factors that reduce O2 solubility in water
- temp
- salinity
- pressure
- organisms living in water
gas exchange system in insects
have tracheae (air passages that extend throughout insect body)
gas exchange system in crabs
have internal gills (open circulatory system)
gas exchange in fish
have internal gills (closed circulatory system)
= lamella on gill filaments increase SA
Explain why countercurrent flow is better than concurrent flow in fish
countercurrent flow: as blood flow in the opposite direction to the water, it always flows next to water that has given up less of its oxygen (so more oxygen can enter the blood)
so exchange is more complete
what is tidal volume
the normal amount of air exchanged when breathing at REST
Most CO2 in blood is carried as . . .
bicarbonate ions
To minimize changes in pH of blood, hemoglobin can bind to CO2 & act as a buffer
What i the Haldane effect?
Increased capacity of blood to carry CO2 when at low oxygen saturation
Properties of hemoglobin that make the removal of CO2 more likely:
- CO2 binds to hemoglobin
- Hemoglobin not carrying O2 (deoxygenated) has a higher affinity for CO2
- The Haldane effect facilitates removal of CO2 at tissues w/ low partial pressure of O2
- Bohr & Haldane effects are results of same phenomena
myoglobin
muscles have their own oxygen storing molecule called myoglobin
Binds ONE oxygen per myoglobin
Increased O2 affinity compared to haemoglobin
Binds oxygen at lower partial pressure (concentration)
Oxygen dissociation curve is to the LEFT of hemoglobin
Respiratory adaptations
How do marine mammals hold their breath for so long during underwater dives?
Increased concentration of hemoglobin
Increased concentration of myoglobin (10x more than in humans)
Reduce their heart rate
Reduce blood flow to extremities & organs
How does COVID-19 affect respiratory system?
- Virus enters lungs
- Virus binds to alveolar wall cells, injects its DNA
- Infected cell produced many copies of virus
- Alveolar cell destroyed, virus particles released & infected neighboring cells
What chemoreceptors? how are they involved in cell communication & breathing?
- found on surface of medulla & are sensitive to the P(CO2) & pH of cerebrospinal fluid
- also found on large vessels leaving the heart & are sensitive to decreased O2 availability
A shift to the right (of dissociation curve)
Bohr effect
High CO2
increased acidity
BPG
