Reproductive Physiology Flashcards
Outline the regulation of reproductive processes by Neural control.
- Nerves release neurotransmitters directly onto the target tissue
- Usually operates via spinal cord
Outline the regulation of reproductive processes via ‘Neuroendocrine control’.
- Combined efforts of nerves and hormones
- Usually operated via spinal cord
- Relies on transort of hormones through circulatory blood
Outline the regulation of reproductive processes via endocrine control.
- Hormones operating independent of the nerves
- Relies on transport of hormones through circulatory blood
Outline the ‘neural reflex’ pathway of regulation of reproductive processes
Stimulus (thermal, tactile, visual) –> Sensory nerve ending –> Afferent neurons –> Spinal cord –> Efferent neurons –> Target tissue –> Neurotransmitters
Outine the pathway (neural/muscular) for ejaculation.
Intromission –> Sensory stimulation of glans penis (temp and pressure –>
Afferent neurons –> spinal cord –> motor neuron –> ischiocavernosus muscle, bulbosporangiosus muscle and urethralis muscle –> expulsion of semen
What is the Neuroendocrine reflex?
Regulation of reproductive processes.
- Sensory nerves synapse with interneurons (I) in the spinal cord
- Efferent neurons travel to the hypothalamus where hypothalamic neurons release neurohormones
- These neurohormones enter the blood and activate target tissues such as the anterior lobe of the pituitary, mammary gland or the epididymis
What is the pathway for milk secretion?
Suckling –> nerve –> hypothalamus –> oxytocin –> lobule (alveolus) –> Milk production
List the Hormones of Reproduction:
Steroid:
- Testosterones
- Oestrogen
- Progesterone
Neuropeptides:
- Gonadotropin-releasing hormone
- Oxytocin
Glycoproteins:
- Follicle stimulation hormone
- Luteinising hormone
Where is the Gonadotropin-releasing hormone produced?
Hypothalamus
Where is the Gonadotropin-releasing hormone released from?
anterior pituitary
What is the role of Gonadotropin-releasing hormone?
Controls the release of gonadotropins (glycoproteins)
What does FSH stimulate?
- Follicular growth in females, hence increases production of oestrogen
- Stimulates Sertoli cells (initiates spermatogenesis) in males
What does luteinising hormone stimulate?
- Induces ovulation of mature follicles, hence formation of C.luteum and production of progesterone
- Stimulates testosterone production in males
What controls the production of sex steroid hormones?
Hypothalamohypophyseal tract via positive and negative feedback of GnRH
Positive = stimulates GnRH release
Negative = suppression of GnRH release
What is the hyothalamohypophyseal tract?
A capillary system connecting the hypothalamus with the anterior pituitary.
What are some physical/physiological responses to testosterone production?
- Male behaviour and aggression
- Spermatogenesis
- Growth of secondary sex glands & muscle
- Development of antlers/horns etc.
What are some effects of Oestrogen production?
- Uterine blood flow
- Growth of uterine endometrial glands
- Secretory activity of oviduct
- Smooth muscle motility
- Sexual receptivity
- Closure of epiphyseal growth plate in bones
- Mammary duct growth
What are some effects of Progesterone release?
- Uterine endometrial gland growth
- Secretory activity of oviduct and endometrial glands
- Mammary lobuloalveolar growth
- Quiescence of uterus
What is the source, target organ/tissue and main effects of Testosterone steroid hormone?
Source: Testes, Ovarian follicles
Target:
(M) Testes, smooth muscle
(F) Brain, granulosa cells, smooth muscle
Main Effects:
(M): Anabolisis, spermatogenesis
(F) Oestrogen synthesis
What is the source, target organ/tissue and main effects of Oestrogen release?
Source:
(M) Testes
(F) Ovarian follicles, placenta
Target:
(M): Brain
(F): Hypothalamus, repro tract, mammary gland
Effect:
(M) Sexual behaviour
(F): Sexual behaviour, GnRH control, repro tract secretion, uterine motility
What is the source, target and effect of progesterone?
Source:
(F) Ovarian CL, placenta
Target: Uterus, mammary gland, hypothalamus
Effect: Uterine secretion, GnRH control, pregnancy maintenance
What is meant by dioestrus?
Period between oestrus cycle
What are the 2 phases of the oestrus cycle?
- Follicular phase
- Luteal phase
What characterises proestrus?
rise in estradiol produced by developing follicles
What is the course of Folliculogenesis?
- Primordial follicle
- Primary follicle
- Secondary follicle
- Tertiary follicle (Antral)
- Graafian follicle (dominant)
What are the follicular cell layers?
- Theca externa - surrounds and supports
- Theca interna - surrounds and supports
- Granulosa - responds to FSH to produce oestrogen & fluid
- Cumulus oophorus - promotes oocyte maturation and ovulation
What is the process of oocyte maturation?
What structures make up an oocyte?
- 1st polar body
- 2nd polar body
- Perivitelline space
- Pronuclei
- Zona pellucida
What controls the regulation of follicular growth?
Follicle stimulating hormone & Luteinising hormone
Recruitment, selection and dominance
(surge center and tonic center - hypothalamus)
Outline the formation of copora lutea.
- Granulosa cells convert to large luteal cells
- Theca cells convert to small luteal cells
- Structure changes from producing oestrogen to now producing progesterone
What is Luteolysis?
Luteolysis–> structural and functional degradation of CL, occurs at the end of the luteal phase of both the estrous and menstrual cycles in the absence of pregnancy.
- CL produces P4 which primes the uterus to produce PGF2a
- PGF2a stimulates formation of Ot receptors on the uterine endometrium
- PGF2a destroys CL
- The presence of an embryo stops this pathway
Outline the structure of the Testes (for spermatogenesis).
Tubular:
- Seminiferous tubules
- Sertoli cells
- Developing germ cells
Interstitial:
- Blood vessels
- CT
- Lymphatics
- Nerves
- Leydig cells
What comprises the spermatozoan?
Head
- Nucleus
- Acrosome
- Perinuclear space
Tail
- Middle piece (mitochondria)
- Principal piece
- Terminal piece
Outline the pathway of sperm transport
Seminiferous tubules –>rete testis –> testis –> efferent ductules –> epididymal duct –> ductus deferens –> Pelvic urethra –> penile urethra
- Immediate transport
- Cervix
- Uterus
- Oviduct –> Fertilisation
What are the functions of the placenta?
Transient endocrine and metabolic organ
- Pregnancy maintenance
- Mammary gland development
- fetal nourishment (gas transport, osmotic eq. acts as foetal organs)
What are the placental hormones?
Progesterone: takes over from CL
- Oestrogen*:
- Produced from androgens supplied by fetus
- Oestrogen levels indicate fetal well being
- Production peaks pre-partuition
Equine Chorionic Gonadotrophin (eCG) - critical for sustained preganancy
Human Chorionic Gonadotrophin
What is important for regulation of parturition?
Progesterone : Oestrogen
- fetal stress
- PFG2alpha and oxytocin
What are the stages of parturition?
-
First stage:
Uterine contractions
Cervic dilates
Vulva swells -
Second stage:
Foetus expelled through birth canal -
Third stage:
Placenta expelled -
After the birth:
Production of colostrum
Involution of the uterus
Why is the production of milk necessary?
agalactica leads to failure to reproduce
Milk has evolved to be the ideal diet
How do mammary glands develop
What control is milk secretion under?
HORMONAL
- Species differences in which hormones are required:
Rat = prolactin and ACTH Rabbt = prolactin Goat/sheep = prolactin, GH, thyrotropin Cattle = prolactin, GH
Tissue growth of juveniles includes:
- CNS: mitotic activity completed by birth,, further development due to hypertrophy of existing cells
- Skeletel system: most in place prior to birth, longitudinal growth post puberty
- Musculature: along with/slightly delayed to bone
- Adipose: max growth occurs post other system development
What are the factors affecting growth?
- Genetic:
- Species
- Breed and strain
- Mother
- Paternal size - Environmental:
- Maternal age (young mothers still growing - compete)
- Maternal size
- Maternal nutrition
- Climatic stress
- Litter size
