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Bio 105: Human Reproduction

Lecture Packet 20

Chapter 17

Outline

• Male Reproduction• Reproductive organs• Sperm development

• Female Reproduction• Reproductive organs• Egg development• Uterine cycle

• Fertilization

Reproductive Terminology

• Gonads = Testes or Ovaries• Produce gametes • Produce hormones

• Testes Testosterone

• Ovaries Estrogen and Progesterone

Reproductive Terminology

• Fertilization• When sperm and egg fuse

• Zygote• Result of fertilization• Will develop into a fetus

Male Reproductive Organs

• Testes

• Epididymis

• Vas deferens

• Urethra

• Penis

• Prostate• Seminal vesicles

• Bulbourethral glands

The Male Reproductive System

Table 17.1

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Male Reproduction - Overview

• Sperm begin their development in the testes

• Undergo further development in the epididymis

• The sperm travel through the vas deferensthen through the urethra and out of the body – ejaculation

• Fluid is secreted along the way from the testes to the urethra

• Fluid + Sperm = Semen

Male Reproductive Organs

• Testes (Testis – Singular)• Produce sperm and testosterone• Sperm begin development here• Contained in a sac (scrotum) surrounded

by muscle• Helps maintain the correct temperature for

sperm development

Male Reproductive Organs

• Testes, Cont’d• Comprised of many tubes

• Seminiferous tubules

• Where sperm begin to develop

• Interstitial cells• Located between the seminiferous tubules

• Produce testosterone

Figure 17.2

Seminiferous tubules

Male Reproductive Organs

• Epididymis• Sperm maturation and storage

• Vas deferens• Conducts sperm from epididymis to the

urethra• Urethra

• Conducts sperm or urine out of the body through the penis

• Penis• Male organ for intercourse and urination

Male Reproductive Organs

• Prostate• Gland that secretes fluid

• Makes semen alkaline

• Activates the sperm and makes them motile

• Seminal vesicles• Gland that secretes fluid

• Makes up most of the volume of semen

• Fluid contains sugar, amino acids and prostaglandins

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Male Reproductive Organs

• Bulbourethral glands• Gland that secretes fluid before

ejaculation• Lubricates the urethra

• Rinses acidic urine from the urethra

Figure 17.1a (2 of 2)

The Male Reproductive System

Vas deferens

• One of a pair of ducts that transport sperm from the epididymis to the urethra

Urethra

• A tube that transports semen during ejaculation, and urine at other times

Penis

• The organ of sexual intercourse that delivers sperm to the female reproductive tract

Testis

• One of a pair of primary reproductive organs (gonads) that produce sperm and testosterone

Epididymis

• One of a pair of ducts in which sperm are stored and mature

Seminal vesicle

• One of a pair of glands that produce a fluid that nourishes sperm, thickens sperm, and assists movement of sperm once in the female reproductive tract

Prostate gland

• A gland that produces alkaline secretions that activate sperm and reduce the acidity of the male and female reproductive system

Bulbourethral gland

• One of a pair of glands that produce a mucous secretion before ejaculation that neutralizes acidic urine in the urethra

Urinary bladder

Rectum

Review Questions

• Where do sperm begin their development?

• Where do they undergo further development?

• What gland secretes the fluid that makes up most of the volume of semen?

• How many chromosomes are in a diploid cell?

Review Questions

• When a diploid cell undergoes mitosis is the resulting cell haploid or diploid?

• When a diploid cell undergoes meiosis is the resulting cell haploid or diploid?

Spermatogenesis

• Occurs in the outer layer of the seminiferous tubules

• Begins with diploid cells called spermatogonia

Spermatogenesis

• Spermatogonis undergo mitosis• Divide into two cells

• One cell stays a spermatogonia• One cell becomes a primary spermatocyte

• Primary spermatocyte undergoes meiosis I • Creates 2 secondary spermatocytes

• Secondary spermatocyte undergoes meiosis II• Creates 4 spermatids

• Structural changes take place to make spermatozoa

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Spermatogenesis

Figure 17.3

Testis

Spermatozoan

Lumen

Uncoiled seminiferous tubule

Cut end of

seminiferous tubule

Late spermatids

Early spermatids

Secondary spermatocyte

(one copy of

each chromosome)

Primary spermatocyte

Spermatogonium

(two copies of

each chromosome)Mitosis

Meio

sis

IM

eio

sis

II

Sperm

• Mature sperm cell has 3 regions• Head

• Contains the DNA

• Coated with acrosome

• Midpiece• Contains high concentration of mitochondria

• Tail• Flagella for movement

Figure 17.4

The Male Reproductive System

The whiplike

movements of the tail

propel the sperm.

The midpiece contains

mitochondria that will

provide metabolic

energy to fuel the trip to

the egg.

The head contains the

father’s chromosomes,

his genetic contribution

to the next generation.

The acrosome, a sac

that covers the head of

the sperm, contains

enzymes that will assist

in fertilization.

Hormonal Regulation in Males

• Gonadotropic-releasing hormone (GnRH)

• Follicle-stimulating hormone (FSH)

• Luteinizing hormone (LH)

• Testosterone

• Inhibin

The Male Reproduction Hormones

Table 17.2

Male Reproductive Hormones

• Gonadotropic-releasing hormone (GnRH)• Produced by hypothalamus• Released by hypothalamus• Target:

• Stimulates the anterior pituitary to secrete LH and FSH

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Male Reproductive Hormones

• Follicle-stimulating hormone (FSH)• Produced by the anterior pituitary• Released by the anterior pituitary• Target

• Stimulates cells in the seminiferous tubules to aid in the production of sperm

Male Reproductive Hormones

• Luteinizing hormone (LH)• Produced by the anterior pituitary• Released by the anterior pituitary• Target

• Stimulates the interstitial cells of the testes to produce testosterone

Male Reproductive Hormones

• Testosterone• Produced by the interstitial cells of the

testes• Function

• Essential for normal development and functioning of the male reproductive organs and sperm

Male Reproductive Hormones

• Inhibin• Produced by the seminiferous tubules in

testes• Released by the seminiferous tubules in

testes• Target

• Inhibits FSH secretion by anterior pituitary gland

Female Reproductive System

• Ovaries

• Oviducts

• Uterus

• Cervix

• Vagina

• Breasts

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The Female Reproductive System

Table 17.3 Figure 17.6b

Oviduct

Ovary

Uterine wall

Uterus

Cervix

Endometrium

Vagina(b) Rear view

The Female Reproductive System

Female Reproduction

• Why do females only produced one egg per month whereas males produce millions of sperm each day?

• Females carry the developing embryo

• Hormones control development of the egg and the preparation of the uterus

Oogenesis

• Born with all the oocytes she will ever have

• As a fetus• Diploid oogonia begin meiosis to form

primary oocytes• Oocytes suspended in Prophase I

• Each month a few oocytes finish meiosis I and develop into a secondary oocyte

• Stay in metaphase II until fertilization

Female Reproductive Organs

• Ovaries• Produce eggs (ova)• Produce female sex hormones

• Estrogen and Progesterone

Female Reprodutive Organs

• Oviduct• Conducts egg• Where fertilization occurs

• Uterus• Developing embryo implants in the

endometrium• Where fetus develops

• Implantation• ~6 days after fertilization• Pregnancy begins at implantation

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Female Reproductive Organs

• Cervix• Opening to the uterus• Dilates to let the fetus pass through

• Vagina• Birth canal• Intercourse organ of the female

• Breasts• Produce milk to feed infant

Oogenesis

• Oocytes• Cells that will become ova (eggs)• Contained in a female’s ovaries inside a

follicle

• Follicles• Groups of cells that support the oocytes

Follicles

• Follicle-stimulating hormone (FSH)• Produced and secreted by anterior

pituitary• Travels to the ovaries • Promotes the development of the follicles

• Follicle develops and starts to produce estrogen

Corpus Luteum

• Ovulation• Approximately every 28 days an oocyte

will leave the ovary

• Follicle stays in the ovary after ovulation• Now called the corpus luteum

Corpus Luteum

• Luteinizing hormone (LH)• Produced by the anterior pituitary• Promotes the development of the corpus

luteum

• Corpus luteum• Releases estrogen and progesterone to

help support the uterus in preparation for the embryo

Corpus Luteum

• If pregnancy• Corpus luteum will be maintained by a

hormone secreted by the embryo• Human chorionic gonadotropin (HCG)

• If no pregnancy• Corpus lutuem will degenerate

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Figure 17.8

The Female Reproductive System

Figure 17.9

The Female Reproductive System

Uterine Cycle

• Days 1 to 5 of the cycle• Estrogen and progesterone are low• Endometrium breaks down• Tissue and blood flows out

• Menstruation

Uterine Cycle

• Days 6 to 13• Increased estrogen produced by the

follicle• Endometrium thickens

• Day 14 +/-• Ovulation occurs

Uterine Cycle

• Days 15 to 28• Progesterone from the corpus luteum

causes the endometrium to continue to develop

• Thick endometrium is ready to receive the developing embryo

• If no embryo• Corpus luteum will regress and stop

producing progesterone and estrogen• Leads to endometrium break down

Female Reproductive Hormones

• Gonadotrophic-releasing hormone (GnRH)

• Follicle-stimulating hormone (FSH)

• Luteinizing hormone (LH)

• Estrogen

• Progesterone

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The Female Reproductive System

Table 17.4

Female Reproductive Hormones

• Gonadotropic-releasing hormone (GnRH)

• Produced by hypothalamus• Target

• Stimulates the anterior pituitary to secrete LH and FSH

Female Reproductive Hormones

• Follicle-stimulating hormone (FSH)• Produced by the anterior pituitary• Released by the anterior pituitary• Travels to the ovaries

• Promotes the development of the follicles

Female Reproductive Hormones

• Luteinizing hormone (LH)• Produced by the anterior pituitary• Released by the anterior pituitiary• Travels to the ovaries• Triggers ovulation• Promotes the development of the corpus

luteum

The Female Reproductive System

Table 17.5

Review Questions

• What reproductive organ conducts the egg from the ovary to the uterus?

• Where does fertilization usually occur?

• What does LH promote the development of?

• What do you call the layer of cells that surround and support the oocytes?

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Fertilization Overview

• Females release one oocyte per month

• Males release an average of 200 million sperm per ejaculation

• First sperm enters egg• Triggers egg to put up a protective barrier• Prevents other sperm from entering the

egg

Fertilization and Pregnancy

• Fertilization• When sperm enters the oocyte

• Pregnancy• When implantation occurs• Usually on the 6th day after fertilization

• Embryo develops into a fetus

Important Concepts

• What are the organs, their locations and their functions of the male reproductive system? Including glands

• What is the function and location of the seminiferous tubules?

• What cells in the testes secrete testosterone?

Important Concepts

• How are sperm formed?• Where does it take place?• What is the path of the sperm as they

leave the body?

• What are the important components of sperm?

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Important Concepts

• How is male reproduction regulated?• What hormones are involved in male

reproduction? Where are they produced? What is their target organ? What is their function?

• Be able to discuss in detail how these hormones are regulated

Important Concepts

• What are all the parts and organs of the female reproductive system? What is their function? What is their location?

• How does an egg develop?

• Where is the oocyte fertilized?

• When and where does a fertilized egg implant?

Important Concepts

• Know the overview of the ovarian and uterine cycles

• What are the hormones important in female reproduction and what are their functions?

• How are reproductive hormones regulated in males and females?

Definitions• Gonads• Gametes• Zygote• Fertilization• Scrotum• Seminiferous

tubules• Semen• Ejaculation• Spermatogonia• Interstitial cells

• Spermatogenesis• Primary

spermatocyte• Secondary

spermatocyte• Spermatids• Spermatozoa• Menstruation• Corpus luteum• Oocytes• Ovaries

• Follicles• Ovulation• Pregnancy• Oogenesis• Oogonia• Primary oocytes• Secondary

oocytes• menopause

The End