Physiology Reproductive System Flashcards
Genotypic vs Phenotypic Sex
Genotypic is the chromosome combination
Phenotypic is based on the physical anatomy and hormones
What determines the sex of the zygote?
The sperm determines the genotypic sex of the zygote
What does bipotential fetus mean and how does that come about?
Bipotential fetus means that fetus can become male or female due to the SRY protein being present or not present
Mullerian ducts
Precursor to ovo-uterine system internal organs
Genital Ridges
Become either ovaries or testes
Wolffian ducts
Precursor to testicular system internal organs
10 weeks gestation for testicular system
Activate SRY gene on Y chromosome, producing testis-determining factor
Genital ridges differentiate into testes
Sertoli cells secrete anti-Mullerian hormone
Leydig cells secrete testosterone, converting Wolffian ducts into seminal vesicles, vas deferens, and epididymis
10 weeks gestation for Ovo-uterine system
Genital ridges become ovaries
Wolffian ducts regress
Mullerian ducts become fallopian tubes, uterus, and upper vagina
Differentiation of External Genitalia: Testicular system
5a-reductase converts testosterone into dihydrotestosterone
Creates penis, penile urethra, and scrotum
Differentiation of external genitalia: Ovo-uterine system
No testosterone causes clitoris, and the labia minora and majora to form
Gametogenesis
Germ cells exist within embryonic gonad
Mitotic divisions increase number of germ cells
Meiosis goes through primary, secondary, and haploid gamete
Different timing of meiosis in spermatogenesis and oogenesis
Hormone control of reproduction
Brain controls reproduction through GnRH and pituitary gonadotropins (FSH and LH)
Spermatogenesis
First starts with mitosis, creating more genetic material.
Second is Meiosis 1, splitting into two secondary spermatocytes with full set of information.
Next is Meiosis 2, making 4 spermatid, each with half of a copy of genetic information.
Lastly, there is spermiogenesis, making a spermatozoa for each spermatid, having a flagella to move around.
Oogenesis
Mitosis first, makes primary oocyte
Meiosis 1 next, makes primary oocyte, stops in prophase 1 before birth
Meiosis 1 finishes after puberty, make secondary oocyte and first polar body
Meiosis 2 begins before sperm penetration, but finishes after sperm penetration, making mature ovum and second polar bodies
Uterus internal anatomy
Pear shaped and 7 cm long and 5 cm diameter
Protection for embryo
Nutritional support for embryo
Vagina internal anatomy
Extends from cervix to external genitalia
Cervix projects from uterus into vaginal canal
Fornix is edges of the cervix
Ovary internal anatomy
Thick outer cortex for gamete production
Inner medulla is the nerves and blood vessels
FSH and LH levels over lifetime
Peaks after birth may be due to high levels of maternal estrogen during fetal development
FSH results in stimulation of granulosa cells to produce estradiol which may ready them for the boost in production at puberty
Age and Oogenesis
At puberty there are about 200,000 primordial follicles per ovary
Forty years later, only about 500 will have been ovulated with the rest decomposing
Phases of the Ovarian cycle
Follicular phase: Proliferation of granulosa cells, development of antrum, and maturation of oocyte
Ovulation: Ripened follicle bursts, releasing oocyte
Luteal phase: Ruptured follicle develops into corpus luteum
Hormonal regulation of ovulation
Hypothalamus and pituitary gland regulate ovarian cycle and ovulation.
GNRH activates the anterior pituitary producing LH and FSH, which stimulate production of estrogen and progesterone by ovaries
Follicular Phase
FSH and LH stimulate follicles to grow
Estradiol has negative feedback on GNRH, FSH, and LH production
Thickens endometrium
There is a dominant follicle
Corona radiata: Granulosa cells attached to oocyte
Meiosis 1 complete
Ovulation phase
LH and FSH stimulate maturation of growing follicles
Estradiol stimulates GNRH, FSH, and LH production
LH surge 24 hours before triggers ovulation
High estrogens become positive feedback, increasing sensitivity of FSH and LH-secreting cells to GNRH
Luteal Phase
LH stimulates formation of corpus luteum from leftover follicular tissue
Granulosa and theca cells differentiate into luteal cells
Progesterone, estrogen, and inhibin inhibits GNRH, FSH, and LH production, also maintaining endometrium
Corpus luteum degenerates into corpus albicans after about 14 days and cycle begins again after that
Follicular Phase Hormones and what they act on
FSH acts on granulose cells, inducing proliferation
LH acts on thecal cells, producing androgens
Estrogen stimulates granulosa cell proliferation
AHM, no development of follicles in this cycle
Follicles and their different types
Primary follicle: Growing, single layer of granulosa cells around oocyte, zona pellucida is clear zone around oocyte
Secondary follicle: Growing, 3-6 layers of granulosa cells, pre-antral, theca appears
Tertiary follicle: Growing. fluid filled antrum appears, one will become dominant follicle
Uterus and Uterine Cycle features
Uterine wall lining: Myometrium
Lining: Endometrium
Endometrial lining: Uterine Cycle
Menses: Bleeding from uterus as endometrium is shed
Proliferative phase: Endometrium grows in preparation for pregnancy
Secretory phase: Endometrial secretions promote implantation
Proliferative phase details (Uterine)
Concurrent with follicular maturation and influenced by estrogens
Endometrium is thin (1-3 mm)
Secretory phase details (Uterine)
Concurrent with luteal phase and dominated by progesterone
Endometrium thickens (6 mm)
Endometrial secretions promote implantation
Phases of the Uterine cycle
Proliferative phase
Secretory phase
Menstrual phase
Menstrual phase (Uterine)
Begins as hormone production by corpus luteum declines
Endometrium becomes necrotic and is shed
When does fertilization occur in ovulation?
24 hours after it happens
What is capacitation
Release of acrosomal enzymes allow sperm penetration of zona pelicula
Timing of fertilization steps
Start: Ovulation
Day 1: Fertilization
Days 2-4: Cell division takes place
Days 4-5: Blastocyst reaches uterus
Days 5-6: Blastocyst implants in uterus lining
Steps of fertilization
Step 1: Sperm and egg plasma membranes fuse, triggering the cortical reaction, first polar body expelled
Step 2: Sperm nucleus moves into cytoplasm of egg
Step 3: Oocyte nucleus completes meiotic division
Step 4: Sperm and egg nuclei fuse to form zygote nucleus, second polar body expelled
Placenta and continuing development details
Chorion, amnion, and yolk
Placenta continues to grow during pregnancy
Embryo obtains oxygen and nutrients from the mother through placenta and umbilical cord
Chorion (Placenta)
Encloses the developing embryo
Amnion (Placenta)
Secretes amniotic fluid, suspending the embryo
Chorionic villi
Forms close connection with endometrium blood vessels
Enzymes from villi break down maternal vessel walls
Placental Hormones list
Human chorionic gonadotropin (hCG)
Human placental lactogen (hPL)
Estrogen and progesterone
hCG and hPL (Placental hormones) details
hCG: Rescues corpus luteum
Stimulates testosterone production by testes in developing male fetus
hPL: Breast development
Alter glucose and fat metabolism to support fetal growth
Parturition (Birth) steps
Step 1: Fully developed fetus points head down usually, can be head up
Step 2: Cervical dilation: Uterine contractions push the head against the softened cervix, stretching and dilating it
Step 3: Delivery: Once fully dilated, the uterus contraction pushes the baby through the vagina
Placenta detaches and is released after the fetus
Labor onset
Stimulated by stretch of cervix
Oxytocin (Hormone)
Stretch stimulates release
Stimulates prostaglandin release
Positive feedback: Contractions stimulate more oxytocin release till fetus is delivered
Penis cross section details
Three cylinders of cavernous erectile tissue
Two dorsal corpora cavernosa
One ventral corpus spongiosum, ends in glans
Epididymis
Sperm maturation
Testicular system anatomy
External: Penis and scrotum
Passageway: Urethra
Accessory glands and ducts: Prostate, seminal vesicle, and bulbourethral
Descent of the testes
Testicle development requires a temperature around 98.6 F, develops within abdominal cavity
Sperm development requires a temperature around 96.6 F
Vas deferens
Passageway into abdomen and delivery to the urethra
Testes
Sperm production: Spermatogenesis
Leydig cells
Interstitial space between coils of the seminiferous tubules
Secrete testosterone
Stimulated by LH from anterior pituitary
Sertoli cells
Maintain blood-testis barrier by enveloping developing sperm cells
Secretion of inhibin or activin
Inhibin inhibits FSH, activin stimulates FSH
Secretion of androgen-binding protein
Binds testosterone within the seminiferous tubules so testosterone will continue to have an effect on spermatogenesis
Blood-testis barrier
Occluding junctions of Sertoli cells form a diffusion barrier
Barrier maintains luminal environment favorable for sperm maturation
Prevents sperm from contacting immune system
Sperm anatomy
Head: Contains chromosomes and acrosomal cap consisting of enzymes, hyaluronidase, necessary for fertilization
Middle piece: Contains mitochondria
Tail: Called flagellum, mobility of the sperm cell
Epididymis
Sperm cells move from the seminiferous tubules to the epididymis to mature
Head: Receives spermatozoa
Body: Coiled tubes pass through the body
Tail: Tubes begin to uncoil to become a single tube called the ductus deferens
Seminal vesicles
Secretes fructose and nutrients to nourish sperm
Prostaglandins to aid contraction and sperm transport
Prostate gland
Buffers
Enzymes
Zinc
Bulbourethral gland
Thick, sticky, alkaline mucus and buffers
Semen details
Each ejaculation releases 2-5 mL of semen
Ejaculate consists of spermatozoa and seminal fluid
Spermatozoa: 15-200 million per mL
Seminal fluid: 60% from the seminal vesicles, 30% from the prostate, 5% from the bulbourethral, and 5% from the epididymis
