MCQ 4 - Reproductive System Flashcards
Functions of the testes
Production of spermatozoa by the process spermatogenesis
Synthesis + secretion of sex hormones
Define spermatozoa
Also called spermatozoon + sperm
Male gametes
Structure of the testis
From ball
Tunica albuginea = layer covering testis
Seminiferous tubule = inside testis, where sperm is made, round structures (200-250 micrometers diameter)
Rete testis = straight tubules connected
Efferent duct = sperm travels through to get to…
Epididymis (head + tail) = sperm travels through to..
Vas deferens to…
Urethra
Define spermatogenesis
Rate
How many days?
Production of sperm
Rate of sperm production - 1000 sperm per second
64 days to complete
Structure of seminiferous tubules
Round structures
Steroli cells
Gonocytes/germ cells
Leydig cells
Cells types within the testes
Leydig cells = outside in interstitial tissues, endocrine part of the testes
Gonocytes/germ cells = going to become sperm
Steroli cells = close contact with germ cells, interact + stimulate germ cells in order to become sperm
Stages of spermatogenesis
Mitosis = diploid cells
Puberty
Meiosis = haploid cells (primary to secondary spermatocytes)
Spermiogenesis = remodelling process
What is spermiogenesis
Process of remodelling Package genetic material, so can be delivered Spermatid to mature sperm Formation of acrosome (enzyme cap) Condensation of nucleus Tail formation
Mechanisms to ensure continuous sperm production
Renewable A0 spermatogonia (very 1st stage/step)
Spermatogenic cycle = sections of tubule, new spermatogonia enter process every 16 days
Spermatogenic wave = spermatogenesis staggered in sections along length of tubule
Hormones involved in spermatogenesis
Hypothalamus = GnRH, gonadotrophin-releasing hormone
(Via portal vessels)
Anterior pituitary = LH, luteinising hormone, FSH, follicle-stimulating hormone
(Peripheral circulation)
Testis
Steroli cells
Control spermatogenesis
Sexual differentiation of male phenotype
Mechanical + nutritional support
Form blood-testis barrier
Special tubular environment
Prevent auto-antibody production
Prevent entry of toxic substances
Produce seminiferous fluidWhen can sperm not be used in IVF (LOCATION)?
Sperm in seminiferous tubule + head of epididymis
Sperm maturation changing in epididymis
Sperm develop ability to swim
Surface changes to sperm head to formation of glycoprotein coat
Metabolism changes - use of glucose stores to eternal fructose
Structure changes - loss of cytoplasmic droplet
Passive movement of sperm through reproductive tract
Passive movement through epididymis
Seminiferous fluid production in tubules + absorption in epididymis
Smooth muscle contractions in epididymal wall
Movement of epididymal cilia
Erection
Arteriolar vasodilation in penis
Increase blood flow to sinuses
Corpus cavernosa
Corpus spongiosum
Parasympathetic nervous controlEjaculation
Smooth muscle contractions - in vas deferens + accessory glands
Sympathetic nervous control
Define accessory glands
Seminal vesicles
Prostate gland
Bulbourethral gland
Composition of seminal fluid
Seminiferous fluid (contains salts ions, K, Na, Cl, HCO3-)
Accessory gland secretions =
Seminal vesicles
Prostate gland
Bulbourethral gland
pH = 7.2 - 7.8
Causes of sperm loss
Distance Unfavourable vagina pH Cervical mucous Loss at ejaculation Female immune system Oviductal fluid movement
Sperm transport in female reproductive tract
Time between mating + fertilisation = 5-60 mins
Aim = get to site of fertilisation in oviduct
Sperm moves 4-5 mm/min
Uterine contractions, promoted by oestrogen, prostaglandins, oxytocin
Uterine, cilia, stimulated by oestrogens
Chemotrophic factors from ovum
Sperm maturation in female reproductive tract
CAPACITATION = lots of tail movement, loss of glycoprotein coat, increased permeability + sensitivity to calcium
ACROSOME REACTION = fusion of acrosome to surface membrane, release digestive enzyme (acrosin + hyaluronidase)
Define oocyte
Cell whose meiotic divisions produce single ovum + 3 polar bodies
Changes to oocyte at fertilisation
Ca2+ released from intracellular stores
Cortical reaction = exocytosis of cortical granules
Hardening of zona pellucida to prevent polyspermy
Complete 2nd meiotic division
Fusion of haploid male + female pronuclei = diploid zygote
Functions of ovaries
Production of oocytes by process oogenesis
Synthesis + secretion of sex hormones
Stages of oogenesis
Oogonium undergoes mitosis = primary oocyte + 1 polar body
(After puberty ⬇️)
Meiosis stimulated by LH + ovulation = secondary oocyte
Meiosis stimulated by sperm entry = polar body + fertilised egg
Trend of germ cells in human ovary, define atresia
Atresia = degeneration of oocytes
Gradually decrease with age
Stages of follicular development
Primordial follicle Primary oocyte Primary follicle Pre-antral follicle (Puberty) Antral follicle Ovulated secondary oocyte
Development/Structure of pre-antral follicle
Middle outwards
Primary oocyte
Zona pellucida
Granulosa cell layers
Thecal cell layers
Development/structure of antral follicle
Primary oocyte
Antrum
Cumulus cells
Hormones involved in controlling follicular development + ovulation
Follicular phase:
Hypothalamus = GnRH
Ovary = oestradiol, androgens, inhibin
Androgens (aromatase) = oestrogens
Effects of LH surge on oocyte
Completes 1st meiotic division
Primary oocyte ➡️ secondary oocyte + 1st polar body
Arrest in metaphase of 2nd meiotic division
Forms cortical granules
Increase collagenase activity, especially stigma region of follicle
Similarities in spermatogenesis oogenesis
Both gametogenesis (completed at puberty)
Principles: mitosis, meiosis, cellular remodelling
Control by hypothalamic-pituitary axis: GnRH, LH, FSH
External influences
Differences in spermatogenesis + oogenesis
Spermatogenesis = continuous production/release of sperm, production of sperm + androgens at same time, large output, mitosis + meiosis activated at puberty, stem cell renewal (infinite gamete number), 1 primary spermatocyte = 4 spermatozoa, continues through adult life
Oogenesis = regular cyclic release of ova at ovulation, cyclic production of ova + steroids, few oocytes released, mitosis completed at birth (all oogonia become primary oocytes, no self-renewal (finite number), 1 primary oocyte = 1 mature ovum, meiosis initiated before birth, gametogenesis ends at menopause
2 ovarian cycles
Menstrual cycle = first day of cycle is menstruation
Oestrous cycle = first day of cycle = oestrus (heat)
What are the 2 menstrual cycle phases + day number + key events?
Follicular/proliferative phase (day 1-14) = growing follicle, oestrogen released = prepares for gamete transport
(Ovulation = day 14) = LH released
Luteal/secretory phase (day 14-28) = corpus luteum, FSH + progesterone released = prepares for implantation
Functions of female reproductive tract
Transport gametes to fertilisation site
Provide site of implantation + embryo development
Structure of uterus
Middle outwards
Endometrium = inner epithelial layer + uterine glands Myometrium = circular + longitudinal smooth muscle layers Serosa = outer connective tissue layer
Changes to uterus during menstrual cycle
Follicular / proliferative phase
Increased contractility of myometrium
Growth + proliferation of endometrium
aqueous secretions (protein filament channels) = help sperm transport + maturation
Cervix relaxes
Changes to uterus during menstrual cycle
Luteal / secretory phase
Decreased myometrium contractility Extensive proliferation of endometrium + blood vessels Viscous secretions (mucous) protein filament mesh = help implantation + early pregnancy Cervix constricts
Factors impacting fertility
Age = puberty + menopause Genetic + developmental factors Pathological factors Physiological factors Pharmacological factors
Physiological changes at puberty
Activates = gonads (reproductive organs), age 9-14
1st = menstruation + ejaculation
Appearance sexual characteristics
Define gonads
Reproductive organs that produce gametes + sex hormones
How is puberty initiated?
Activation = GnRH neurones + hypothalamic-pituitary-gonad (HPG) axis
Increased freq. + amplitude of GnRH impulses
Increased release of LH, FSH, adrenal + gonadal sex steroid hormones
What’s the importance of HPG axis in puberty?
Delay in puberty in suppressing HPG activity
Precocious puberty if HPG axis stimulated prematurely
Abnormalities in sex chromosomes + differentiation
Klinefelter’s syndrome
XXY karyotype
Impaired testicular development
Infertile
Abnormalities in sex chromosomes + differentiation
Turner’s syndrome
XO karyotype
Impaired ovarian development
Infertile
Pathological factors impacting fertility
Obstructive diseases Chlamydia Thyroid hormone disorders Autoimmune disease Smoking (toxins - pesticides) Diabetes Spinal injury Cryptorchidism - testes fail to descend Varicoceles - enlarged vein in testes
Physiological factors impacting fertility
Pregnancy = inhibitory effects of progesterone on HPG axis Lactation = inhibitory neuroendocrine reflex
Pharmacological factors impacting fertility
Manipulating menstrual cycle:
Steroidal contraceptives (high dose progesterone / low dose oestrogen)
Inhibit ovulation = negative feedback
Viscosity of cervical + uterine secretions
