Human Anatomy and Physiology Chapter 27 – Reproductive System

Human Anatomy Human Anatomy and Physiologyand Physiology

Chapter 27 – Reproductive Chapter 27 – Reproductive SystemSystem

The Reproductive SystemThe Reproductive System

Functions:Functions: Produce sex cells (eggs and sperm)Produce sex cells (eggs and sperm) Permit the joining of the sex cells Permit the joining of the sex cells Provide an environment for the Provide an environment for the

development of a fertilized egg development of a fertilized egg (only in the female)(only in the female)

Male Reproductive SystemMale Reproductive System

The male The male gonadsgonads (organs that (organs that produce sex cells) are the produce sex cells) are the testestestes..

The testes are held within the The testes are held within the scrotumscrotum Optimum sperm production occurs at Optimum sperm production occurs at

about 3° C cooler than internal body about 3° C cooler than internal body temperaturetemperature

The scrotum helps to regulate the The scrotum helps to regulate the temperature of the testestemperature of the testes

The dartos and cremaster musclesThe dartos and cremaster muscles

Figures 27.1 and 27.2Figures 27.1 and 27.2


The penis contains erectile tissue – The penis contains erectile tissue – Figure 27.4Figure 27.4


Inside the testes there is a series of Inside the testes there is a series of coiled tubes called coiled tubes called seminiferous seminiferous tubules (ST)tubules (ST) these are the site of sperm productionthese are the site of sperm production they have a total length of nearly half they have a total length of nearly half

a mile!a mile! Outside the ST are the Outside the ST are the interstitialinterstitial or or

Leydig cellsLeydig cells that produce that produce testosteronetestosterone

Figure 27.3Figure 27.3

Male Reproductive System Male Reproductive System (cont.)(cont.)

Spermatogenesis Spermatogenesis about 400 million sperm are produced about 400 million sperm are produced

each day!each day! Inside the ST there are two cell types:Inside the ST there are two cell types:

Spermatogenic cells – these will become Spermatogenic cells – these will become spermsperm

Sertioli cells (sustentacular cells) – help Sertioli cells (sustentacular cells) – help nourish the germ cellsnourish the germ cells They also form the blood-testis barrierThey also form the blood-testis barrier



Germ CellsGerm Cells Spermatogonia – around the Spermatogonia – around the

periphery of the STperiphery of the ST Divide by mitosis to start the process of Divide by mitosis to start the process of

sperm productionsperm production One cell One cell spermatocyte, One cell spermatocyte, One cell

spermatogoniaspermatogonia The spermatocytes then proceed The spermatocytes then proceed

through meiosis to produce through meiosis to produce functional sperm cellsfunctional sperm cells



Mature sperm have three distinct parts:Mature sperm have three distinct parts: head - nucleus and head - nucleus and acrosomeacrosome midpiece - contains mitochondriamidpiece - contains mitochondria tail - flagellum for motilitytail - flagellum for motility Figure 27.9Figure 27.9


Sperm produced in the testes mature Sperm produced in the testes mature in the in the epididymisepididymis They are also stored here for as long as They are also stored here for as long as

several monthsseveral months the epididymis is connected to the the epididymis is connected to the

urethra by a long tube called the urethra by a long tube called the vas vas deferens (ductus deferens)deferens (ductus deferens) vasectomyvasectomy - severing of the vas - severing of the vas

deferensdeferens Figure 27.1 and Figure from other Figure 27.1 and Figure from other

texttext


Before leaving the body, sperm are Before leaving the body, sperm are mixed with a fluid mixed with a fluid seminal fluid + sperm = seminal fluid + sperm = semensemen


Seminal fluid is produced by three Seminal fluid is produced by three glands:glands: seminal vesiclesseminal vesicles – (60%) mucus, fructose, – (60%) mucus, fructose,

fibrinogen, prostaglandinsfibrinogen, prostaglandins prostate glandprostate gland – (30%) enzymes, clotting – (30%) enzymes, clotting

factorsfactors bulbourethral glandbulbourethral gland – (5%) mucus – (5%) mucus

The remaining 5% of semen is The remaining 5% of semen is composed of spermcomposed of sperm Normal sperm count is 75-400 million sperm per Normal sperm count is 75-400 million sperm per

ml of semenml of semen



Hormonal Regulation in MalesHormonal Regulation in Males Hypothalamus – Gonadotropin-Hypothalamus – Gonadotropin-

releasing hormone (GnRH)releasing hormone (GnRH) Stimulates the release of the Stimulates the release of the

gonadotropins from the anterior gonadotropins from the anterior pituitary gland:pituitary gland:

Luteinizing Hormone (LH)Luteinizing Hormone (LH) – increases – increases testosterone production in the Leydig testosterone production in the Leydig cellscells

Follicle-Stimulating Hormone (FSH)Follicle-Stimulating Hormone (FSH) – – binds to Sertioli cells and stimulates binds to Sertioli cells and stimulates sperm cell productionsperm cell production



Puberty – onset of sexual Puberty – onset of sexual maturitymaturity Human chorionic gonadotropin is Human chorionic gonadotropin is

produced by the placenta during produced by the placenta during fetal developmentfetal development This stimulates the release of This stimulates the release of

testosterone for initial male sex testosterone for initial male sex organ developmentorgan development

After birth, very little After birth, very little testosterone is produced until testosterone is produced until pubertypuberty


At puberty the hypothalamus increases At puberty the hypothalamus increases GnRH secretionGnRH secretion

This in turn increases LH and FSH This in turn increases LH and FSH secretion resulting in testosterone secretion resulting in testosterone productionproduction

Effects of testosteroneEffects of testosterone Development and enlargement of male Development and enlargement of male

reproductive systemreproductive system Stimulates hair production on face, legs, Stimulates hair production on face, legs,

chest, pubic region (and back, chest, pubic region (and back, occasionally)occasionally)


Increases rate of sebaceous gland Increases rate of sebaceous gland secretionsecretion

Can result in acneCan result in acne Increases metabolism, RBC Increases metabolism, RBC

production, and protein synthesisproduction, and protein synthesis Causes rapid bone growth (but also Causes rapid bone growth (but also

stimulates the closure of the stimulates the closure of the epiphyseal growth plate)epiphyseal growth plate)

Female Reproductive SystemFemale Reproductive System

The female gonads are the The female gonads are the ovariesovaries the ovaries alternate in the ovaries alternate in

producing one egg per monthproducing one egg per month The ovaries also produce The ovaries also produce

estrogenestrogen and and progesteroneprogesterone (the (the female sex hormones)female sex hormones)

Anatomy - Figures 27.11 and Anatomy - Figures 27.11 and 27.1427.14

Female Reproductive System Female Reproductive System (cont.)(cont.)

OogenesisOogenesis There are many There are many folliclesfollicles within the within the

ovariesovaries each follicle contains an immature eggeach follicle contains an immature egg there are about 2 million follicles at birththere are about 2 million follicles at birth 300,000-400,000 at puberty300,000-400,000 at puberty only ~400 are ever released as mature eggsonly ~400 are ever released as mature eggs

the egg is released from the ovaries the egg is released from the ovaries during during ovulationovulation

The corpus luteum is a hormone-The corpus luteum is a hormone-secreting gland in the ovarysecreting gland in the ovary



PubertyPuberty Marked by menarche (the first Marked by menarche (the first

menstrual period)menstrual period) Reproductive organs and breasts Reproductive organs and breasts

enlarge and developenlarge and develop Puberty results from estrogen Puberty results from estrogen

and progesterone productionand progesterone production


The Menstrual Cycle The Menstrual Cycle Typically the cycle lasts 28 daysTypically the cycle lasts 28 days Includes both the ovarian and uterine Includes both the ovarian and uterine

cyclescycles


The Ovarian Cycle:The Ovarian Cycle: Days 1-14 are the Follicular PhaseDays 1-14 are the Follicular Phase Day 14 – OvulationDay 14 – Ovulation Days 14-28 are the Luteal PhaseDays 14-28 are the Luteal Phase


The Follicular PhaseThe Follicular Phase Early in the cycle GnRH secretion Early in the cycle GnRH secretion

increasesincreases Effect?Effect?

FSH and LH stimulate the FSH and LH stimulate the development of a follicle and development of a follicle and

The production of estrogen by the The production of estrogen by the ovaryovary


A surge of LH results in ovulationA surge of LH results in ovulation It also leads to the development of the It also leads to the development of the

corpus luteumcorpus luteum The corpus luteum secretes estrogen and The corpus luteum secretes estrogen and

progesteroneprogesterone If fertilization does not occur, the If fertilization does not occur, the

cells of the corpus luteum degeneratecells of the corpus luteum degenerate Estrogen and progesterone secretion Estrogen and progesterone secretion

then rapidly declines and the cycle starts then rapidly declines and the cycle starts overover



The Uterine Cycle:The Uterine Cycle: Days 1-5: Menstrual PhaseDays 1-5: Menstrual Phase

the endometrium is sloughed off the endometrium is sloughed off Days 6-14: Proliferative PhaseDays 6-14: Proliferative Phase

endometrium thickens and prepares for endometrium thickens and prepares for pregnancypregnancy

Caused by estrogen and progesteroneCaused by estrogen and progesterone Days 15-28: Secretory PhaseDays 15-28: Secretory Phase

endometrium continues to thicken and endometrium continues to thicken and secretions increasesecretions increase

Figure 27.22, Figure from other text, and Figure 27.22, Figure from other text, and CDCD


Menopause - period when uterine Menopause - period when uterine cycles and ovulation ceasecycles and ovulation cease usually occurs between the ages of 45 usually occurs between the ages of 45

and 55and 55

Fertilization and PregnancyFertilization and Pregnancy

Fertilization occurs in the fallopian Fertilization occurs in the fallopian tubes tubes If the egg is fertilized, human chorionic If the egg is fertilized, human chorionic

gonadotropin is releasedgonadotropin is released This keeps the corpus luteum from This keeps the corpus luteum from

degenerating and stops the uterine degenerating and stops the uterine cyclecycle

The embryo can become embedded in The embryo can become embedded in the uterine wallthe uterine wall

Figures from other text and 28.4Figures from other text and 28.4


Timing of intercourse:Timing of intercourse: The egg is only viable for 12-24 hours The egg is only viable for 12-24 hours

after ovulationafter ovulation Sperm cells can survive for 24-72 Sperm cells can survive for 24-72

hourshours Therefore intercourse must occur Therefore intercourse must occur

between days 11-15 in the menstrual between days 11-15 in the menstrual cyclecycle

Even given the right timing, Even given the right timing, fertilization is not certainfertilization is not certain Figure 28.2 and other figureFigure 28.2 and other figure


Twins:Twins: Fraternal – 2 eggs released Fraternal – 2 eggs released

and fertilizedand fertilized Identical Twins – 1 egg Identical Twins – 1 egg

separates to form 2 babiesseparates to form 2 babies Figures from other textFigures from other text

Methods of Birth ControlMethods of Birth Control

Table and Figures from other textTable and Figures from other text

Methods of Birth ControlMethods of Birth Control

DiscussionDiscussion

InfertilityInfertility

15% of all couples in the US cannot have 15% of all couples in the US cannot have childrenchildren these couples would be considered these couples would be considered sterilesterile

Another 10% have fewer children than they Another 10% have fewer children than they wishwish these couples are termed these couples are termed infertileinfertile

The most frequent causes of infertility in The most frequent causes of infertility in females are:females are: blocked oviductsblocked oviducts endometriosis - presence of uterine tissue endometriosis - presence of uterine tissue

outside the uterusoutside the uterus The most frequent cause of infertility in The most frequent cause of infertility in

males is:males is: low sperm countlow sperm count

Alternative Methods of Alternative Methods of ReproductionReproduction

Artificial Insemination - sperm Artificial Insemination - sperm are placed in the vagina by a are placed in the vagina by a physicianphysician sperm from donorsperm from donor concentrated sperm from husband concentrated sperm from husband

with low sperm countwith low sperm count In Vitro Fertilization - sperm and In Vitro Fertilization - sperm and

egg are mixed in a test tubeegg are mixed in a test tube fertilized egg is placed in the fertilized egg is placed in the

female’s uterusfemale’s uterus

Alternative Methods of Alternative Methods of Reproduction (cont.)Reproduction (cont.)

Gamete Intrafallopian Transfer - Gamete Intrafallopian Transfer - eggs and sperm are mixed in a eggs and sperm are mixed in a test tubetest tube they are immediately injected into they are immediately injected into

the fallopian tubesthe fallopian tubes Surrogate Mothers - individuals Surrogate Mothers - individuals

donate eggs and/or spermdonate eggs and/or sperm the surrogate mother carries the the surrogate mother carries the

fetusfetus

Documents

Human Anatomy and Physiology Chapter 27 – Reproductive System