21. Chapter 26- Reporduction and Development Flashcards
What are the 3 sets of structures male and female sex organs consist of?
Gonads: gamete producing organs (testes in makes, ovaries in females)
Internal genitalia: accessory glands and ducts
External genitalia: external reproductive structures
How is sex determined?
We have 22 pairs of autosomes and 1 pair of sex chromosomes
Females XX
Males XY
Slides 9-12 March 15
What is X chromosome inactivation?
In females, after the development of the ovaries, one X chromosome is turned off in each cell (only one x is expressed in every cell)
slide 13 March 15
What are the steps of being pregnant for the baby?
Slide 14 March 15
What is the sex differentiation during development?
Reproductive structures do not begin to differentiate until the seventh week of development and prior to this time are considered bipotential
Slide 15 March 15
What is the SRY gene?
What are the 3 hormones?
Sex determining Region of the Y chromosome (SRY)
Anti-medullary hormone (sertolj cells): causes Müllerian ducts to regress
Testosterone (leydig cells): converts wolffian ducts into male accessory structures (epididymis, vas deferens, seminal vesicles)
Dihydrotestosterone (leydig cells): differentiation of external genitalia
Slides 16-18 March 15
How is the development of the external genitalia formed?
Genital tubercle forms clitoris in females and glans penis in males
Urethral folds and grooves form labor minors, opening of vagina and urethra in women and forms shaft of penis in men
Labioscrotal swellings form labia majora in females and form shaft of penis and scrotum in males
Slides 19-20 March 15
study differentiation summary with SRY gene into different sexes on slide 4 March 18
okay
What is dihydrotestosterone (DHT)?
defective gene for 5a-reductase
despite having testosterone production, lack of DHT results in failure of male external genital and prostate development (appears to be female at birth)
At puberty the testes begin to secrete testosterone again causing masculinization
What is the differences between testis and ovaries?
Ovaries- some of largest cells in body
Non motile, move via smooth muscle contractions or cilia
Born with all the oocytes you will have, cyclically released during reproductive years
After ~40 years ceases
Testis- quite small
Only flagellated cells in the body and are highly motile
Continuously produced after reaching reproductive maturity
Sperm and testosterone production diminishes with age but do not cease
Slide 6 Mar 18
What is gametogenesis?
4 steps?
Production of gametes
Mitosis begins in utero to increase germ cell numbers
- Germ cells in embryonic gonads undergo mitotic divisions to increase number
- duplication of chromosomes (92 chromosomes)
- One primary gamete divides into two secondary gametes (each with 46 chromosomes)
- Secondary gametes divide again to produce haploid gametes (23 chromosomes=23 chromatids)
Slides 7-8 Mar 18
What is female gametogenesis?
Slides 9-12 Mar 18
Germ cells are called oogonia
Mitosis and 1st stage of meiosis occurs in 5th month of fetal development
~500000 primary oocytes
Meiosis resumes at puberty
First division produces large secondary oocytes and tiny first polar body (46 chromosomes)
The egg begins second meiotic division, polar bodies break down
Ovary relaxes egg and doesn’t undergo secondary division until fertilized
What is male gametogenesis?
Slides 13-15 mar 18
At birth the testes contain only immature germ cells and remain quiescent
At puberty germ cell mitosis resumes producing germ cells known as spermatogonia
Some spermatogonia continue in mitosis, some enter meiosis producing primary spermatocytes, secondary spermatocytes, spermatids and sperm
What directs reproduction?
The brain
Reproductive system has complex control pathways in the body with multiple hormones interaction in an ever-changing fashion
Begins with secretion of peptide hormones from hypothalamus and anterior pituitary that control gondal secretion of sex hormones including androgens, estrogens and progesterone
Both sexes produce all 3
What is the hypothalamic pituitary gonadal axis?
Gonadotrophon releasing hormone (GnRH) produced in hypothalamic neurons controls secretion of two anterior pituitary gonadotrophins from gonadotropes
Slide 17 Mar 18
What are the 3 steps of control pathways?
- Neurons synthesizing trophic neurohormones release them into capillaries of the portal system
- Portal veins carry the trophies neurohormones directly to the anterior pituitary, where they act on the endocrine cells
- Endocrine cells release their peptide hormones into the second set of capillaries for distribution to the rest of the body
Slide 18 Mar 18
What are feedback pathways?
Short-loop negative feedback involves LH and FSH inhibiting GnRH release from the hypothalamus
Estrogen negative feedback up to a point, but once reaching higher concentrations flips to positive feedback driving GnRH and especially LH even higher
Slides 19-20 Mar 18
How is GnRH released?
Released from hypothalamus in pulsatile fashion every 1-3 hours in both sexes
Females also have a surge corresponding with ovulation
Children with GnRH deficiency will not mature sexually without gonadtrophin stimulation of gonads (synthetic GnRH must be silvered in pulsatile manner)
Slide 3 March 20
Study the anatomy of male reproduction slide 5-6 Mar 20
Ok
What is the prostate?
Probably the best known accessory gland due to its medical significant
Prostate cancer is most common for men
DHT involved in prostate development
Administration of 5a-reductase inhibitor (finasteride) blocks DHT production, shrinks hypertrophied prostate
Study the anatomy of the testis slide 8-9 March 20
Ok
What are Sertoli cells?
Found in the seminiferous tubule (slide 8-9 March 20)
contain tight junctions with adjacent Sertoli cells forming s blood testis barrier between lumen and interstitial space
Regulate sperm development
Provide a variety of substances: hormones (activin and inhibin), growth factors, enzymes, androgen binding protein
How is sperm produced?
Germ cells (spermatogonium) reside just inside the basal lamina of seminiferous tubules
Some remain here undergoing mitosis to make more germ cells, some every meiosis to become primary spermatocytes
As spermatocytes differentiate to sperm they move towards the tubule lumen
Sertoli right junctions break and reform around the migrating cells
Once reaching lumen one spermatogonium becomes 4 spermatids
Spermatids remain embedded in apical membrane of Sertoli cells while they complete transformation
Spermatogonium to free sperm
Slides 11-13 March 20
Study anatomy of sperm cell slide 13 March 20
Ok
What is the oath of FSH and LH secreted by the anterior pituitary?
Slide 15 March 20
What is semen?
The mixture done by the sperm leaving the vas deferens being joined by secretions of accessory glands
Liquid medium for delivering sperm
Protects reproductive tract from pathogens ascending urethra
What are the 5 accessory gland secretions?
- Nutrients
- Buffers for protection against acidic vaginas environment and residual acidic urine in urethra
- Chemicals to increase sperm motility
- Prostaglandins (motility and contraction of male and female reproductive tracts)
- Immunoglobulins, lysozyme and other antibacterial compounds
What are the primary sex characteristics and secondary sex characteristics?
Primary- internal sexual organs and external genitalia, which we learned are differentiated to male during embryonic development by androgens and their growth after puberty is also due to androgens
Secondary- body shape, facial and body hair growth, muscular development, thickening of vocal chords (lowering of voice), behavioural effects
Study the anatomy of the female reproductive system slides 4-7 March 22
Ok
How are the follicles developed?
Number of oogonia during fetal development, primordial follicles, and pirinordual follicles at puberty
5-7 million oogonia during Fetal development
500000 primordial follicles (primary oocytes) at birth
180000 primordial follicles at puberty
Primordial follicles are recruited each cycle
Ovaries contain follicles in different developmental states
As secondary follicle develops “antrum” forms to become tertiary
A single tertiary dominant follicle fully develops
Slides 8-9 March 22
What is the menstrual cycle?
What is the ovarian cycle phases?
Females produce mature gametes in monthly cycles (28 days)
3-7 days of bloody uterine discharge
Follicular phase: marked by follicular growth, most variable 10 days to 3 weeks
Ovulation: once one or more follicles have ripened, the ovary releases oocyte(s) during ovulation
Luteal phase: (post ovulating phase) ruptured follicle transforms to corpus luteum (yellow) names for yellow pigment and lipid deposits
Slides 10-12 March 22
What are the uterine cycle phases?
Menses: beginning of the follicular phase in ovary corresponds with menstrual bleeding from uterus
Proliferation phase: latter part of the follicular phase, the uterus adds new cells to the endometrium later in anticipation of pregnancy
Secretory phase: after ovulation hormones from corpus luteum covert thickened endometrium into a secretory structure
(If pregnancy doesn’t occur the superficial endometrium layers are lost during menstruation and the cycle begins again)
Slides 13-14 March 22
What are the hormones involved in the mistrial cycle?
GnRH from hypothalamus
FSH and LH from the anterior pituitary
Estrogen, progesterone, inhibin and AMH from the ovary
During follicular stage estrogen is dominant
Ovulation is triggered by surges in LH and FSH
During luteal phase progesterone dominant
What is day 1 in the menstrual cycle?
What happens?
First day of menstruation
FSH is released, several tertiary follicles mature
Granulosa (FSH) and thecal (LH) cells begin to produce hormones
Androgens (androstenedione) converted to estrogens (aromatase) in granulosa cells
AMH prevents additional follicle recruitment
Estrogen negative feedback anterior pituitary, positive on granulosa cells
Slide 16-17 March 22
What is ovulation?
Occurs 16-24 hours after LH peak
LH necessary for oocyte maturation
Meiosis resumes
Mature follicle secreted prostaglandins and proteolytic enzymes
Proteolytic enzymes breakdown collagen and connective tissue holding follicle together
Prostaglandins May contribute to rupture of follicle and /or ovary wall
Secondary oocyte is swept into Fallopian tube by fimbrae
Slides 18-20 March 22
