1. erection, ejacultion and copulation Flashcards
list muscles of the penis and their anatomical locations/functions
- paired ischiocavernosus muscle: originates at ischial arch and inserts on root of penis. forces glood into the corpus cavenosum and corpus spongiosum
- urethralis and bulbospongiosus: surrounds some of urethra and transports semen
- paired retractor penis muscle: originates at caudal vertebrae and inserts on sigmoid flexure or distal penis. allows retraction/protrusion of the penis
what is libido
behavioural manifestation of sexual interest
what is intromission
entrance of penis into the vagina
what is erection
firming and enlargement of the penis
what is emission
movement of accessory gland fluid into male urethra to mix with sperm
what is ejaculation
reflex expulsion of sperm from male reproductive tract
outline the sequence of events in precopulatory behaviour
- search for sexual partner
- courtship
- sexual arousal
- erection
- penile protrusion
overall erection requires
- elevated arterial blood inflow
- dilation or corporal sinusoids
- restricted venous outflow
- elated intra-penile pressure
- relaxation of the retractor penis muscle
explain the mechanism behind erection
- erectile tissue is surrounded by a heavy capsule of varying thickness called tunica albuginea
- connective tissue trabeculae penetrate the erectile tissue and break up the space into sinusoids
- sinusoids are lined by endothelium
- engorgement of cavernous tissue causes a blockage of venous return
- ischiocavernosus muscle contraction compresses penile veins
- intermittent contractions causes pump like action at base of penis
- blood build up in corpus cavernosum and exceptionally high pressures
what happens to blood vessels and nerves in flaccid penis
helicine arteries empty into venous sinuses but
- lumen of helicine arteries obliterated by sympathetic tone of muscles in the vessel walls
- adrenergic nerves secrete norepinephrine
- norepinephrine causes vasoconstriction of helecine arteries so no filling of blood into sinuses
how does the nervous system induce erection
- parasympathetic fibres inhibit (relax) longitudinal muscle fibres in helecine arteries
- blood flows into the central sinusoids
- swllelling
- results in compression of oblique veins
- further penile swelling
what is essential for erection in the dog
contraction of vestibule muscles in the female
what is the principle neurotransmitter involved in the erectile process
nitric oxide
outline the steps in copulatory behaviour
- mounting
- intromission
- ejaculation
how is nitric oxide used to drive the erectile process
- parasympathetic nerve innervates helecine arteries
- nerve terminals release nitric oxide
- NO stimulates guanylate cyclase to convert GTP into cGMP
- cGMP causes smooth muscle of helecine arteris to relax
- sinuses engorge
- intracorporal pressure increases
- venules and veins are compressed
outline which parts of the penis enlarge during erection in each species
intromission is aided by
- relaxation of the retractor penis muscle
- penile lengthening (pigs/ruminants)
- engorgement (stallion)
- os penis (dog)
outline the process of ejacuation
- stimulation of the glans enis via the internal pudendal nerve to lumbosacral region of the spinal cord
- firing of nerves within the spinal cord
- reflex innervation of urethralis muscle and ischiocavenosus muscle
outline the features of ejaculate in the stallion, boar and dog
outline the process of copulation and ejaculation in the dog
outline the steps in postcopulatory behaviour
- dismount
- refractory period
- memory
how does erection dissipate
- sympathetic tone predominates again
- closure of helecine arteries
- blood flows out of sinusoids and erection subsides slowly
