Reproduction Flashcards
Steroids
Made from cholesterol in adrenal cortex, testis, ovary, placenta
Mode of action:
- Freely enter target cells
- Interacts with specific receptor molecules inside cell
- Receptor hormone complex -> nucleus
Progestagens
Prepare uterus to receive embryo and maintains uterus during pregnancy
Stimulates mammary gland growth (suppresses milk secretion)
Regulates secretions of gonadotrophins (FSH, LH) produced by pituitary gland
Androgens
Differentiation of male tissue in embryo and secondary sexual characteristics
Supports spermatogenesis
Influences aggressive and sexual behaviour
Regulates secretions of gonadotrophins (FSH, LH)
Oestrogens
Secondary sexual characteristics
Prepare uterus for sperm transport
Stimulate growth and activity of mammary gland, gonads and endometrium
Regulates of gonadotrophins (FSH, LH)
Eicosanoids
Derived from arachidonic acid (AA) Local hormone (half life 10 mins) Leukotrienes and prostaglandins
Prostaglandins
Erection and ejaculation Luteal regression Ovulation Uterine contraction Uterine contraction Cervical softening Milk ejection
Protein and peptide hormones
Mode of action:
- Via plasma membrane receptors binding to receptors generate secondary messengers
- Activation of kinases
- Phosphorylates proteins -> physiological action
Glycoproteins: FSH, LH
Polypeptide: ACTH, prolactin (PRL)
Peptides: Gonadotrophin-releasing hormone (GnRH), oxytocin (OT)
Hypothalamic
Small part of brain - behavioural and stress responses
Neuroendocrine centre
Many pass to pituitary gland for processing
Cortico-release hormone (CRH)
Stimulates ACTH secretion (ACTH -> adrenal gland -> cortisol)
Growth hormone releasing hormone (GHRH)
Stimulates growth hormone release
Dopamine (DA)
Inhibit prolactin release
Gonadotrophin releasing hormone (GnRH)
Stimulates LH and FSH release
Half life 7 mins
Pulsatile secretion
- Neural control -> pulsatile release
- Non-neural control -> more sustained release
Synthesised by nerve cell bodies in hypothalamus -> arterial pituitary via blood -> anterior pituitary secrete LH, FSH
FSH (follicle stimulating hormone)
Growth and maturation of ovarian follicle
Acts mainly on granulosa (surrounds oocyte) cells of follicle
Artificially stimulate multiple ovulation for IVF
Affects spermatogenesis in testis - acts on Sertoli cells
Stimulates formation of oestradiol in ovary and testis (with LH)
Luteinising hormone
Pulsatile secretion - frequency and amplitude vary - control ovarian cycle
Pre-ovulation surge of LH -> follicle rupture and ovulation
Regulates progesterone synthesis after ovulation in CL
Stimulates formation of oestradiol in ovary with FSH
Regulate testosterone synthesis in testis - Leydig cells
Oxytocin-uterine contraction
Afferent sensory nerve impulse -> spinal cord -> midbrain -> produced in hypothalamus -> posterior pituitary -> myometrium to contract
Oxytocin - milk ejection reflex
Neural hormonal reflex
Afferent sensory nerve impulses -> spinal cord -> midbrain -> hypothalamus -> neurosecretory cells to discharge oxytocin form axons end in posterior pituitary -> bloodstream -> stimulates myoepithelial in ducts of lactating mammary glands to contract
Milk from alveoli to ducts to nipple to infant
Stimulate increased prolactin secretion - duct development and milk synthesis
Sertoli cells
Inside seminiferous tubules
Spermatocytes receive testicular proteins via Sertoli cell gap junction
Spermatocytes and spermatids physically attached to Sertoli cells
Removes material from elongating spermatid during cytoplasmic condensation - removal of excess cytoplasm
All linked by gap junctions - communication throughout tubule
Mediate actions of hormones on spermatogenesis
Spermatogenesis
Mitotic proliferation:
- Large numbers of spermatogonia (diploid) produced
- Basal compartment of tubule
Meiotic division:
- Spermatocytes -> spermatids
- Adluminal compartment of tubule
Cytodifferentiation:
- Packages genes for delivery to oocyte
- Elongating spermatid -> spermatozoa
Testosterone
Synthesised by Leydig cells - between seminiferous tubules
Passes into blood and seminiferous tubules
Sertoli cells convert testosterone -> dihydrotestosterone - passes into testicular fluid - stimulate male reproductive tract
LH stimulate Leydig cells to make testosterone
FSH stimulates production of androgen receptor proteins in Sertoli cells
Epipdidymal maturation
Sperm structure: loss of surplus cytoplasm, condenstaion of nuclear chromatin
Sperm membranes: surface glycoproteins added, membrane fluidity and lipid compisition change
Metabolism: Depressed - prolong life, increased dependence on external fructose
Motility: increase cAMP content of tail
Seminal plasma composition
(From prostrate, seminal vesicles, ampulla)
Glycoproteins - decapacitation factors
Fructose and sorbital - energy
Citric acid - stops cell coagulation
Acid phosphatase - phospholipid metabolism
Buffers
Ascorbic acid - protect sperm from oxidation
Prostaglandins - muscle contraction in female tract
Penis shaft
Corpus cavernosum - main body
Corpus spongiosum - urethra
Blood reservoirs during erection
Fibroelastic penis
Bull, boar, ram
Limited erectile tissue, sigmoid flexure
Sigmoid flexure
Retract penis inside body until erection
Help by retractor penis muscle
Contract - held in
Relax - protrusion