Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 46: Animal...

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Chapter 46:

Animal Reproduction


Figure 46.8 Insect reproductive anatomy

(a) Male honeybee. Sperm form in the testes, pass through the sperm duct (vas deferens), and are stored in the seminal vesicle. The male ejaculates sperm along with fluidfrom the accessory glands. (Males of somespecies of insects and other arthropods haveappendages called claspers that grasp thefemale during copulation.)

(b) Female honeybee. Eggs develop in the ovaries and then pass through the oviducts and into the vagina. A pair of accessory glands (only one is shown)add protective secretions to the eggs in the vagina. After mating, sperm are stored in the spermatheca, a sac connected to the vagina by a short duct.

Testis1

Accessorygland

3 Seminalvesicle

Vas deferens2 Penis5

Ejaculatoryduct

4

Accessorygland

Spermatheca

Ovary1

Vagina3

Oviduct2


Vagina

Uterus

Cervix

OvariesOviduct

Uterine wallEndometrium

Follicles

Corpus luteum


Figure 46.10 Reproductive anatomy of the human male

Erectile tissueof penis

Prostate gland

(Urinarybladder)

Bulbourethral gland

Vas deferensEpididymisTestis

Seminalvesicle(behind bladder)

Urethra

Scrotum

Glans penis


Figure 46.11 Human Oogenesis

Ovary

Primary germ cell in embryo

Differentiation

OogoniumOogoniumin ovary

Mitoticdivision

Primary oocyte,arrested in prophaseof meiosis I(present at birth)

Completion of meiosis Iand onset of meiosis II

Primaryoocytewithinfollicle

Secondary oocyte,arrested at meta-phase of meiosis II

Firstpolarbody

Ovulation

Entry ofsperm triggerscompletion ofmeiosis II

Ovum

Growingfollicle

Mature follicle

Rupturedfollicle

Ovulatedsecondary oocyte

Corpus luteum

Degeneratingcorpus luteum

2n

2n

nn

nnSecondpolarbody


EpididymisSeminiferous tubule

Testis

Cross sectionof seminiferoustubule

Sertoli cellnucleus

Lumen ofSeminiferous tubule

Spermatogonium

Primary spermatocyte(in prophase of meiosis I)

Secondary spermatocyte

Earlyspermatids

Spermatids(at two stages ofdifferentiation)

Differentiation(Sertoli cells providenutrients)

Meiosis II

Meiosis I completed

Mitotic division,producing large numbersof spermatogonia

Sperm cells

Acrosome

NucleusMitochondria

Neck

TailPlasma membrane

Head Midpiece

2n

2n

n n

nnnn

n n n n

Differentiation andOnset of meiosis I

Figure 46.12 Human Spermatogenesis


Figure 46.14 Hormonal control of the testes

Stimuli from otherareas in the brain

Hypothalamus

GnRH from thehypothalamus reg-ulates FSH and LH

release from theanterior pituitary.

FSH acts on theSertoli cells of the

seminiferoustubules, promotingspermatogenesis.

LH stimulates the Leydig cells to maketestosterone, whichin turn stimulatessperm production.

Anteriorpituitary

Negativefeedback

Leydig cellsmake

testosteronePrimary andsecondary sexcharacteristics

Sertoli cells

Spermatogenesis Testis


Figure 46.17 Human fetal development

5 weeks. Limb buds, eyes, the heart, the liver, and rudiments of all other organs have started to develop in the embryo, which is only about 1 cm long.

(a) 14 weeks. Growth and development of the offspring, now called a fetus, continue during the second trimester. This fetus is about 6 cm long.

(b) 20 weeks. By the end of the second trimester (at 24 weeks), the fetus grows to about 30 cm in length.

(c)


Figure 46.18 A model for the induction of labor

Estrogen Oxytocin

fromovaries

from fetusand mother'sposterior pituitary

Induces oxytocinreceptors on uterus

Stimulates uterusto contract

Stimulatesplacenta to make

Prostaglandins

Stimulate morecontractions

of uterus

Pos

itive

fee

dbac

k


Figure 46.19 The three stages of labor

PlacentaUmbilicalcordUterusCervix

Dilation of the cervix

Expulsion: delivery of the infant

UterusPlacenta(detaching)

Umbilicalcord

Delivery of the placenta

1

2

3

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 46: Animal...

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