1. Reproductive System and Development

2. Figure 33.3 Sexual Reproduction Requires the Production of Haploid Gametes through Meiosis
(a) Spermatogenesis produces haploid sperm. (b) Oogenesis produces haploid eggs (ova).

3. Urinary bladder (excretory system)
Figure 27.4A
Urinary bladder (excretory system)
Seminal vesicle (behind bladder)
Prostate gland
Bulbourethral gland
Urethra
Erectile tissue of penis
Figure 27.4A Front view of male reproductive anatomy
Scrotum
Vas deferens
Epididymis
Testis
Glans of penis 3

4. Rectum (digestive system)
Figure 27.4B
Rectum (digestive system)
Seminal vesicle
Urinary bladder (excretory system)
Vas deferens
Ejaculatory duct
Pubic bone (skeletal system)
Prostate gland
Erectile tissue
Figure 27.4B Side view of male reproductive anatomy (with nonreproductive structures in italic)
Bulbourethral gland
Anus (digestive system)
Urethra (excretory system)
Penis
Vas deferens
Epididymis
Glans of penis
Testis
Testicle
Prepuce
Scrotum 4

5. Cross section of seminiferous tubule
Figure 27.5A_1
Penis
Epididymis
Seminiferous tubule
Testis
Scrotum
Testis
Figure 27.5A_1 Spermatogenesis (part 1)
Cross section of seminiferous tubule 5

6. Figure 27.5A Spermatogenesis
Penis
Epididymis
Seminiferous tubule
Testis
Scrotum
Testis
Diploid cell 2n
Differentiation and onset of meiosis I
Primary spermatocyte 2n
Cross section of seminiferous tubule
(diploid; in prophase of meiosis I)
Meiosis I completed
Secondary spermatocyte n n
Figure 27.5A Spermatogenesis
(haploid)
Meiosis II
Developing sperm cells n n n n
Differentiation
Sperm cells n n n n
(haploid)
Mature sperm released into center of seminiferous tubule 6

7. Urethral region here expands and fills with semen
Figure 27.4C
Sphincter contracts
Urinary bladder
Urethral region here expands and fills with semen
Contractions of vas deferens
Contractions of seminal vesicle
Contractions of prostate gland
Contractions of epididymis
Sphincter contracts 1
Sphincter remains contracted
Semen expelled
Figure 27.4C The two stages of ejaculation
Contractions of muscles around base of penis
Contractions of urethra
Sphincter relaxes 2 7

8. Stimuli from other areas in the brain
Figure 27.4D
Stimuli from other areas in the brain
Hypothalamus
Releasing hormone
Anterior pituitary
Negative feedback
FSH LH
Figure 27.4D Hormonal control of the testis
Androgen production
Testis
Sperm production 8

9. Endometrium (lining of uterus)
Figure 27.3A
Oviduct
Ovaries
Follicles
Corpus luteum
Uterus
Wall of uterus
Endometrium (lining of uterus)
Cervix (“neck” of uterus)
Figure 27.3A Front view of female reproductive anatomy (upper portion)
Vagina 9

10. Rectum (digestive system) Urinary bladder (excretory system)
Figure 27.3C
Oviduct
Ovary
Uterus
Rectum (digestive system)
Urinary bladder (excretory system)
Pubic bone (skeletal system)
Cervix
Urethra (excretory system)
Vagina
Figure 27.3C Side view of female reproductive anatomy (with nonreproductive structures in italic)
Shaft
Prepuce
Clitoris
Glans
Vulva
Labia minora
Labia majora
Anus (digestive system)
Vaginal opening 10

11. Differentiation and onset of meiosis I
Figure 27.5B_1
Before birth
Ovary
Diploid cell
Differentiation and onset of meiosis I
Primary oocyte within follicle
Primary oocyte
Figure 27.5B_1 Oogenesis and the development of an ovarian follicle (part 1)
(arrested in prophase of meiosis I; present at birth) 11

12. Completion of meiosis I and onset of meiosis II
Figure 27.5B_2
Growing follicle
Completion of meiosis I and onset of meiosis II
Mature follicle
Ruptured follicle
First polar body
Figure 27.5B_2 Oogenesis and the development of an ovarian follicle (part 2)
Secondary oocyte
(arrested at metaphase of meiosis II; released from ovary)
Ovulated secondary oocyte 12

13. (arrested at metaphase of meiosis II; released from ovary)
Figure 27.5B_3
Ruptured follicle
First polar body
Secondary oocyte
(arrested at metaphase of meiosis II; released from ovary)
Ovulated secondary oocyte
Entry of sperm triggers completion of meiosis II
Second polar body
Figure 27.5B_3 Oogenesis and the development of an ovarian follicle (part 3)
Corpus luteum
Mature egg (ovum)
Degenerating corpus luteum 13

14. Figure 29.9 The Human Menstrual Cycle Depends on the Sequential Release of Several Hormones
Follicle-stimulating hormone (FSH) launches a new menstrual cycle by stimulating the growth of ovarian follicles. Developing follicles produce estrogen. When estrogen levels reach a certain threshold, they trigger release of luteinizing hormone (LH) from the pituitary, which triggers ovulation. An estrogen, especially the large amounts of progesterone secreted by the corpus luteum, stimulates a buildup of the uterine lining in preparation for a possible pregnancy. If fertilization fails to occur, the corpus luteum dies after about 14 days, hormone concentrations crash, and the uterine lining is sloughed off.

15. Figure 33.4 Fertilization Occurs When a Single Sperm Enters the Egg
(a) Sperm are many times smaller than eggs, as can be seen in this scanning electron micrograph of a swarm of sperm surrounding a single human egg. (b) The tail of a sperm consists of a whiplike flagellum, which helps it wriggle into the uterus and through the oviduct to meet the egg. The acrosome contains enzymes that help the sperm penetrate the egg’s outer covering. (c) Although many sperm are present on the surface of the egg, only one can penetrate to fertilize the egg.

16. The sperm’s acrosomal enzymes digest the egg’s jelly coat.
Figure 27.9C 1
A sperm touches the egg’s jelly coat, and its acrosome releases enzyme molecules. 2
The sperm’s acrosomal enzymes digest the egg’s jelly coat. 3
Proteins on the sperm head bind to egg receptors. 4
The plasma membranes of sperm and egg fuse.
Acrosomal enzymes 5
The sperm nucleus enters the egg cytoplasm.
Sperm
Plasma membrane 6
The vitelline layer separates and becomes impenetrable.
Nucleus
Acrosome
Receptor protein molecules
Plasma membrane
Sperm nucleus
Figure 27.9C The process of fertilization in a sea urchin n
Vitelline layer
Cytoplasm n
Jelly coat
Egg nucleus n 7
The nuclei of sperm and egg fuse. n
Egg cell 2n
Zygote nucleus 16

17. Figure 27.10_s1
Zygote
2 cells
Figure 27.10_s1 Cleavage in a sea urchin (step 1) 17

18. Zygote 2 cells 4 cells 8 cells Figure 27.10_s2
Figure 27.10_s2 Cleavage in a sea urchin (step 2) 18

19. Many cells (solid ball)
Figure 27.10_s3
Zygote
2 cells
4 cells
8 cells
Figure 27.10_s3 Cleavage in a sea urchin (step 3)
Many cells (solid ball) 19

20. Blastula (hollow ball) Cross section of blastula
Figure 27.10_s4
Zygote
2 cells
4 cells
8 cells
Figure 27.10_s4 Cleavage in a sea urchin (step 4)
Many cells (solid ball)
Blastocoel
Blastula (hollow ball)
Cross section of blastula 20

21. Table 27.11
Table Derivatives of the Three Embryonic Tissue Layers 21

22. Figure 33.7 Cell Differentiation in the Blastocyst Produces the Embryo and Portions of the Placenta
The mammalian blastocyst has two types of tissue, whose fates become evident after the blastocyst is implanted in the endometrium. The inner cell mass begins to differentiate into the actual embryo. The trophoblast expands into the endometrium to begin forming a placenta in conjunction with endometrial tissues.

23. Figure 33.8 The Three Tissue Layers Have Developmentally Distinct Fates
Despite differences in the patterns of early cell division, almost all animals have recognizable layers of endoderm, mesoderm, and ectoderm cells that appear as parts of the blastocyst differentiate into specialized tissue types. During gastrulation, these tissue layers are rearranged as cells migrate to occupy their proper positions in the embryo.

24. Figure 33.9 The Placenta Is the Life-Sustaining Connection between Mother and Developing Fetus
Through the placenta, the fetus receives oxygen and nutrients from the mother’s bloodstream and disposes of wastes. Note that there is no intermingling of the maternal and fetal blood vessels. Gases, nutrients, and wastes diffuse into and out the intervillous space, the pools of blood that bathe the chorionic villi.

25. Figure 33.10 Nine Months in the Womb
For convenience, this period is traditionally divided into three trimesters, each 3 months long.