1. both asexual and sexual reproduction occur in the ... · fertilization occurs in the oviduct. 24...

Asexual reproduction involves the formation of individuals whose genes all come from one parent.

There is no fusion of sperm and egg.

Sexual reproduction is the formation of offspring by the fusion of haploid gametes.

Ovum: female gamete - usually large and nonmotile.

Spermatozooan: male gamete - usually small and motile.

Sexual reproduction increases genetic variation among offspring.

1. Both asexual and sexual reproduction occur in

the animal kingdom

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Advantages of asexual reproduction:

Can reproduce without needing to find a mate

Can have numerous offspring in a short time

In stable environments, allows for the perpetuation of

successful genotypes.

Sexual reproduction’s advantage occurs in changing

environments where variation provides the natural

selection process with adaptive choices.


Reproductive Anatomy of the Human Male.

The scrotum and the penis are the external components of the reproductive system.

The internal reproductive organs consist of gonads, accessory sex glands, and ducts.

Here we see many examples of how structure is related to function.

Let’s watch

1. Human reproduction involves intricate

anatomy and complex behavior


../Animations/Animation 46.1 Male Reproduc.MOV

So let’s get a blank piece of paper and test

your artistic ability. Draw and label these:

• Penis

• Testes

• Scrotum

• Epididymis

• Urethra

• Vas deferens (sperm ducts)

• Prostate gland and seminal vesicle


Fig. 46.8

Testes are the male gonads.

Consist of many highly coiled

seminiferous tubules surrounded by

layers of connective tissue.

Sperm form inside seminiferous

tubules.

Leydig cells (aka interstitial cells),

scattered between seminiferous

tubules produce androgens, mainly

testosterone.


Testes are located in the scrotum,

outside the body cavity.

This keeps testicular temperature

cooler than the body cavity,

which is best for sperm

production.

The testes develop in the body

cavity and descend into the

scrotum just before birth.


From the seminiferous tubules

sperm pass to the coiled tubules of

the epididymis.

It takes about 20 days for sperm

to pass through the tubules of the

epididymis.

In the epididymis sperm become

motile (but not fully) and gain

the ability to fertilize.


Ejaculation propels sperm from the epididymis to

the vas deferens (aka - sperm ducts).

The vas deferens run from the scrotum and behind

the urinary bladder.

Here each vas deferens joins with a duct from

the seminal vesicle to form an ejaculatory

duct.

The ejaculatory ducts open into the urethra.

The urethra drains both the excretory and

reproductive systems.


Accessory sex glands add

secretions to semen.

A pair of seminal vesicles

contribute about 60% of total

semen volume.

Seminal fluid is alkaline.

It contains mucus, fructose, a

coagulating enzyme, ascorbic

acid, and prostaglandins.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The prostate gland secretes directly

into the urethra.

Prostatic fluid contains anticoagulant

enzymes and citrate.

Prostate problems are common in males

over 40.

Prostate enlargement occurs in nearly

all males over 70.

Prostate cancer is the most common

cancer in men.


So let’s get a blank piece of paper and test

your artistic ability. Draw and label these:

• Penis

• Testes

• Scrotum

• Epididymis

• Urethra

• Vas deferens (sperm ducts)

• Prostate gland and seminal vesicle

Let’s try the blank paper art work again.

Here are the EOC female parts…

• Vagina

• Cervix

• Uterus

• Oviducts (Fallopian tubes)

• Ovaries

Fig. 46.9


Ovaries are the female gonads, homologous to testes.

Located in the abdominal cavity. Let’s watch

Flanking, and attached by mesentery to, the uterus.

Each ovary is enclosed in a tough protective capsule.

Each ovary contains follicles.


../Animations/Animation 46.2.1 Female Repr.MOV

Each follicle consists of one egg cell surrounded by one or more layers of follicle cells.

Follicles produce the primary female sex hormones: estrogens.

Follicle cells nourish and protect the developing egg cell.

A woman is born with about 400,000 follicles.

Only several hundred will release eggs during a female’s reproductive years.


Usually one follicle matures and releases its egg during

each menstrual cycle.

After ovulation the remaining follicular tissue develops

into the corpus luteum, Latin for “yellow body”.

It secretes estrogens and progesterone.

This maintains the uterine

lining during pregnancy.

If pregnancy does not

occur the corpus luteum

disintegrates.


Fig. 46.10

At ovulation the egg is released into the abdominal

cavity near the opening of the oviduct. Let’s watch

The cilia-lined funnel-like opening of the oviduct

draws in the egg.

Cilia convey the egg through the oviduct to the

uterus.

Endometrium: highly vascularized inner lining

of the uterus.

The neck of the uterus, the cervix, opens into

the vagina.

The vagina is a thin-walled chamber that forms

the birth canal and is the repository for sperm

during copulation.


../Animations/Animation 46.2.5 Female Repr.MOV

Let’s try the blank paper art work again.

Here are the EOC female parts…

• Vagina

• Cervix

• Uterus

• Oviducts (Fallopian tubes)

• Ovaries

Spermatogenesis is the production of mature sperm cells from spermatogonia.

This is a continuous and prolific process in the adult male.

Each ejaculation contains 100 – 650 million sperm.

Occurs in seminiferous tubules.

As spermatogenesis progresses the developing sperm cells move from the wall to the lumen of a seminiferous tubule.

2. Spermatogenesis and oogenesis both

involve meiosis but differ in three

significant ways


Fig. 46.11


Sperm structure:

Haploid nucleus.

Tipped with an acrosome.

Contains enzymes that help the

sperm penetrate to the egg.

A large number

of mitochondria

provide ATP to

power the

flagellum.


Fig. 46.12

Oogenesis is the production of ova from oogonia.

Differs from spermatogenesis in three major ways:

At birth an ovary contains all of the primary oocytes it

will ever have.

Unequal cytokinesis during meiosis results in the

formation of a single large secondary oocyte and three

small polar bodies.

The polar bodies degenerate.

Oogenesis has long “resting” periods. Meiosis starts in

all cells before a woman is born, but it stops in

Prophase I, and doesn’t continue until the menstrual

cycle starts.


Fig. 46.13


From Conception to Birth.

In placental mammals, pregnancy is the condition of

carrying one or more embryos.

Pregnancy is preceded by conception (fertilization)

and continues until birth.

A human pregnancy averages 266 days.

4. Embryonic and fetal development occur

during pregnancy in humans and other eutherian

(placental) mammals


Human gestation is divided into three trimesters.

First trimester.

Fertilization occurs in the oviduct.

24 hours later the zygote begins cleavage.

3- 4 days after fertilization it reaches the uterus; the

embryo is a ball of cells called a morula.

It takes about 1 week past fertilization for the

blastocyst, a hollow ball of cells, to form.

After 5 more days it implants in the endometrium.


Fig. 46.16


Items may refer to the early

stages of development

(implantation, morula,

blastocyst, gastrulation,

neurulation) but will not

assess the definition of

these terms.

For the first 2 – 4 weeks of development the embryo

obtains nutrients from the endometrium.

Then the placenta provides for the diffusion of material

between maternal and embryonic circulations. Amnion?

Umbilical cord? All three are on the EOC list.

Fig. 46.17


Organogenesis occurs during the first

trimester.

By week 4: the heart is beating.

By the end of week 8: all of the

major structures of the adult are

present in rudimentary form.

The rapidity of development makes

this a time when the embryo is

especially sensitive to environmental

insult.Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Here’s my first grandchild, Lilly, at the end

of the first trimester.

Second trimester.

Fetus grows rapidly, but not MOST

rapidly, and is very active.

Cartilage begins to be replaced by

bone.

Placenta now takes over the

secretion of progesterone, which

maintains the pregnancy.


Third trimester.

Period of MOST RAPID growth.

Fetal activity may decrease as the fetus fills the space available to it.

Maternal abdominal organs become compressed and displaced.

Terminates with parturition (fancy name for birth).

A decrease in progesterone levels triggers the release of oxytocin, then this POSITIVE feedback starts…


Hormonal regulation of birth.

Fig. 46.19


Parturition occurs as a result of labor.

First stage: opening

up and thinning

of the cervix.

Ending in complete

dilation.

Second stage:

Expulsion of the

baby as a result

of strong uterine

contractions.

Third stage:

Expulsion of the placenta.

Fig. 46.20Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Pregnancy is divided into periods called trimesters.

Which of the following occurs during the second

trimester of pregnancy?

A. The blastula forms

B. The fetus begins to move

C. The major organs begin to develop

D. The fetus has regular breathing motions

The main function of the male reproductive system

is to produce and deliver sperm for fertilization.

Which of the following gives the path of sperm cells

through the male reproductive system?

a. testicle, epididymis, vas deferens, urethra

b. Epididymis, testicle, vas deferens, urethra

c. Testicle, epididymis, urethra, vas deferens

d. Testicle, vas deferens, epididymis, urethra

Eggs are the female reproductive cells.

Where in the body are egg cells stored?

A. Cervix

B. Uterus

C. Ovaries

D. Fallopian tubes

A female egg undergoes several stages before it is

successfully implanted. In which structure of the female

human reproductive system is the egg fertilized by a

sperm?

A. Ovary

B. Uterus

C. Vagina

D. Fallopian tube

A fertilized egg undergoes several stages before it is

successfully implanted. The diagram below shows these stages

as the fertilized egg travels through the female human

reproductive system. In which of the following structures of

the female human reproductive system is the blastocyst

implanted during normal human development?

A. ovary

B. uterus

C. vagina

D. amniotic sac

Which structure of the male

reproductive system produces sperm?

A. Ovaries

B. Testicles

C. Scrotum

D. Penis

1. both asexual and sexual reproduction occur in the ... · fertilization occurs in the oviduct. 24...

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