BIOL 1051H Lecture Notes - Lecture 2: Seminiferous Tubule, Basal Metabolic Rate, Underarm Hair
Reproduction Physiology
Reproduction Physiology
●Genetic Sexes
○Sexual reproduction is biparent, meaning offspring receives genes from two
parents
■Offspring is not genetically identical to either on
○Gametes (sex cells) produced by each parent
○Male and female gametes (sex cells) combine their genes to form a zygote
(fertilized egg)
●Puberty
○First few years of adolescence, until the first menstrual period for girls or the first
ejactulation of viable sperm in boys
■Age 14 in boys and 12 in girls
■Surge of pituitary gonadotropins (FSH, LH) awakens the reproductive
system, leading to onset of puberty
○Physical Characteristics of Puberty in males
■Growth of sex organs
■Testosterone stimulates generalized body growth
■Erythropoiesis, basal metabolic rate, and increase in appetite
■Pubic hair, axillary hair, and facial hair develop in response to
dihydrotestosterone (DHT)
■Stimulates sperm production and libido (sex drive)
Endocrine Control of Puberty
●Follicle Stimulating Hormone (FSH)
○Stimulates sustentacular cells to secrete androgen-binding protein that binds
testosterone, keeping it in seminiferous tubule lumen to stimulate spermatogenesis
●Luteinizing Hormone (LH)
○Stimulates interstitial cells in testes to produce testosterone
●Endocrine Control of Sexual Function
○Adulthood
■Testosterone sustains that male reproductive tract, sperm production, and
libido
■Inhibin from sustentacular cells suppresses FSH output from the pituitary,
reducing sperm production without reducing LH and testosterone secretion
●Testosterone secretion declines with age
●Male andropause (climacteric) may occur
○A period of declining reproductive function that may be first seen is early
50s
○Drop in testosterone and inhibin triggers rise in FSH and LH
■Mood changes, hot flashes
●Spermatogenesis: process of sperm production in seminiferous tubules of testes
●How are sperm produced
○Produced in testis
○Optimal at 2-3 degrees lower than body temp
○Takes around 64 days
○200 million per day
○Further mature in epididymis
●Spermatogenesis
○Type B spermatogonia becomes a primary spermatocyte
○Primary spermatocyte undergoes meiosis 1 which gives rise of two secondary
spermatocytes.
○Each secondary spermatocyte undergoes meiosis 2 dividing into two spermatids
○Spermiogenesis: discard excess cytoplasm and grow a tail- mature spermatozoa
●The Mature Spermatozoa
○Head contains;
■Nucleus
■Acrosome: enzyme cap that contains enzymes that penetrate the egg
○Tail contains:
■Midpiece contain mitochondria
■Axoneme (flagella)
●Seminal Fluid: 90 % of fluid expelled during orgasm
○Water
○Lubricant: Mucous
○Buffers: Neutralize acid- activate sperm
○Nutrients (fructose and other sugars)
○Prostaglandins: Smooth muscle contraction
●The female reproductive
○Puberty begins at 8-10
○Triggered by an increase in GnRH which stimulates anterior pituitary FSH and
LH
○FSH stimulates ovarian follicles and they being to secrete estrogen, progesterone,
inhibin, and a small amount of androgen
●Stages of Puberty in Women
○Thelarche
■Onset of breast development, the earliest noticeable sign of puberty
Document Summary
Sexual reproduction is biparent, meaning offspring receives genes from two parents. Offspring is not genetically identical to either on. Gametes (sex cells) produced by each parent. Male and female gametes (sex cells) combine their genes to form a zygote (fertilized egg) First few years of adolescence, until the first menstrual period for girls or the first ejactulation of viable sperm in boys. Age 14 in boys and 12 in girls. Surge of pituitary gonadotropins (fsh, lh) awakens the reproductive system, leading to onset of puberty. Erythropoiesis, basal metabolic rate, and increase in appetite. Pubic hair, axillary hair, and facial hair develop in response to dihydrotestosterone (dht) Stimulates sperm production and libido (sex drive) Stimulates sustentacular cells to secrete androgen-binding protein that binds testosterone, keeping it in seminiferous tubule lumen to stimulate spermatogenesis. Stimulates interstitial cells in testes to produce testosterone. Testosterone sustains that male reproductive tract, sperm production, and libido.
