Reproductive Physiology

Topics Introduction Types of reproduction Reproductive cycle Sexual behaviour/sexual act (Read Notes) Components of sexual act in males (Read Notes) Puberty

Introduction Why do we need to reproduce? - Important for the propagation of species - Allows hereditary traits from both parents to be inherited by offspring

Types of Reproduction AbsentPresentRecombination of genes NonePresentGametes OneBothParents AsexualSexualAttributes

Reproductive Cycle Puberty Coitus Pregnancy Parturition Lactation Weaning Puberty/ Coitus PregnancyParturition Lactation Weaning

Sexual Behaviour/Sexual Act EPOR E – Excitement Phase (somatogenic or psychogenic stimulus) P – Plateau Phase (maximum sexual excitement) Orgasmic Phase (ejaculation and climax of sexual excitement with involuntary rhythmic pelvic muscle contractions lasting a few secs Resolution phase (resting/refractory phase) – in males, they have to rest before another erection occurs. In women, this phase will only occur after multiple orgasms

Components of sexual act in males Erection Ejaculation (Two phases – emission and expulsion)

Erection Engorgement of penis with blood Erection reflex - a spinal reflex triggered by mechanoreceptors on glans penis Tactile stimulation on glans triggers parasymphatetic activity Vasodilation is rapid and full erection achieved in 5 – 10 seconds Bulbourethral gland secretes mucus for lubrication Reflex can be stimulated/inhibited by nervous centre that have the final nervous pathway in the autonomic nerves (innervates the penile arteriole e.g., erection can occur due to sight or a seductive memory without stimulation of glans penis) Reflex can also be inhibited even though glans penis is stimulated e.g., impotence. This condition is usually more influenced by psychology rather than physical impairment (damage to nerve supply that disturbs the autonomic function and circulation problems to the penis)

Erection reflex Stimulation of mechanoreceptors in glans penis Parasymphatetic supply Parasymphatetic supply Symphatetic to bulbo-urethral to penile arterioles supply to penile and urethral glands arterioles Mucus Penile arterioles dilate Lubrication Erection Compresses veins

Ejaculation (1) A spinal reflex Occurs when excitement stage reach a climax Consists of two phases:emission phase and expulsion phase Emission phase – Symphatetic impulse will cause sequences of smooth muscle contraction at prostate gland, vas deferens and seminal vesicles. The prostatic fluid, seminal vesicles fluid and spermatozoa will drained into urethra

Ejaculation (2) Expulsion phase – The sphincter at the bladder will close to prevent semen from entering urethra with urine - Entry of semen into urethra will trigger impulses that activates skeletal muscles at the base of the penis - Rhythmic contractions of these muscles (intervals of 0.8 s) together with pressure on pelvis will cause ejaculation

Component of male sex act DefinitionAccomplished by ErectionHardening of the normally flaccid penis to permit its entry into the vagina Engorgement of the penis erectile tissue with blood as a result of marked parasymphatetically induced vasodilation of the penile arterioles and mechanical compression of veins Ejaculation Emission phase Expulsion phase Emptying of sperm and accessory sex gland secretions (semen) into urethra Forceful expulsion of semen from penis Symphatetically-induced contraction of the smooth muscle in walls of the ducts and accessory sex glands Motor-neuron-induced contraction of the skeletal muscles at the base of the penis

Puberty (1)/adolescence Morphology, physiology and behavioral changes that occurs to an individual Rapid changes of adolescence start gradually, 9 to 11 years old for girls, 13 years old for boys. Hormone changes responsible actually begin some years earlier and may produce periods of moodiness and restlessness Girls start these changes before boys and will, for the first three or four years, appear to be maturing much faster. Male growth spurt two years later than female

Physical changes Sign of puberty (female) – menstruation (first time), male (first ejaculation usually without sperm) After 2-4 years, other changes occurs to the body and sexual organs Changes dependent on sex steroids from gonads and adrenal glands and also growth hormone Adolescent growth spurt – minimum growth velocity, peak height velocity, decreased growth velocity and cessation of growth at epiphyseal fusion Shoulders broader in men, hips broader in women Lean body mass (1.5X > in males), body fat (2X > in females), skeletal mass (1.5X > in males). Is that why men are stronger?

Secondary Sexual Characteristics Growth and development of breasts Growth and change in sexual organs Monthly periods, vaginal secretions Moustache, beard Change in voice pitch (lower and deeper in boys) Activation of sweat glands (acne and body odour) Development of body hairs (auxillary etc) and pubic hair Testosterone influences male secondary sexual characteristics while estrogen is for female These changes occurs at different age in different individuals

Stages of puberty (females)

Stages of puberty (males)

Common problem faced by adolescents Emotional problems (Depression) Sexual Problems Boys more aggressive than girls Both have sexual desires A few years after attaining puberty, if a pair of adolescents have sex, the girl will become pregnant REALLY! YES! REALLY!….this is because the ovaries have release ova and the testes have produce spermatozoa If fertilization occurs, then this will result in an unwanted pregnancy

–Behaviour problems What do I do with you!!!! I don’t know you anymore! Don’t worry Mom, I’m just going through a phase

Eating problems Drugs, solvents and alcohol Abuse - Any physical, emotional and sexual abuse may occur in adolescence and may cause many of the problems mentioned -Families with these problems need expert advice and should seek help. -It is important to remember that once a child or teenager has been subjected to any form of abuse, they grow up to become abusers themselves

Adolescence Health Problems High blood pressure Glandular fever Obesity Orthodonthics Other health problems when active in sports Gynaecological and menstrual problems