Reproduction and Development

Chapters 46 and 47 Campbell 9th

Figure 46.10

(Rectum)CervixVagina

Major vestibular(Bartholin’s) gland

Vaginal opening

Oviduct

OvaryUterus

(Urinary bladder)

(Pubic bone)

Urethra

BodyGlansPrepuce

Clitoris

Labia minoraLabia majora

Ovaries Oviduct

Follicles

Corpus luteumUterine wallEndometrium

Vagina

Uterus

Cervix

Figure 46.11b

Seminal vesicle

(Rectum)Vas deferens

Ejaculatory ductProstate glandBulbourethral gland Vas deferens

EpididymisTestisScrotum

(Urinary bladder)

(Urinary duct)

(Pubic bone)

Erectiletissue

Urethra

Glans

Prepuce

Penis

Gametogenesis, the production of gametes, differs in male and female, reflecting the distinct structure and function of their gametes

Sperm are small and motile and must pass from male to female

Eggs are larger and carry out their function within the female

Gametogenesis

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Spermatogenesis, the development of sperm, is continuous and prolific (millions of sperm are produced per day; each sperm takes about 7 weeks to develop

Oogenesis, the development of a mature egg, is a prolonged process

Immature eggs form in the female embryo but do not complete their development until years or decades later

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Spermatogenesis differs from oogenesis in three ways

◦ All four products of meiosis develop into sperm while only one of the four becomes an egg

◦ Spermatogenesis occurs throughout adolescence and adulthood

◦ Sperm are produced continuously without the prolonged interruptions in oogenesis

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EpididymisSeminiferous tubule

Testis

Cross section ofseminiferous tubule

Sertoli cellnucleus

Lumen ofseminiferous tubule

Plasmamembrane

Tail

Neck

Midpiece Head

Mitochondria

NucleusAcrosome

Primordial germ cell in embryo

Mitotic divisions

Spermatogonialstem cell

Spermatogonium

Mitotic divisions

Mitotic divisions

Primary spermatocyte

Meiosis I

Meiosis II

Spermatids (two stages)

Secondary spermatocyte

Earlyspermatid

Sperm cell

Differentiation(Sertoli cellsprovide nutrients)

2n

2n

2n

n n

n n n n

n n n n

Figure 46.12a

Primordial germ cell in embryoMitotic divisions

Spermatogonial stem cell

Spermatogonium

Mitotic divisions

Mitotic divisions

Primary spermatocyte

Meiosis I

Meiosis II

Secondary spermatocyte

Earlyspermatid

Sperm cell

Differentiation(Sertoli cellsprovide nutrients)

2n

2n

2n

n n

n n n n

n n n n

Figure 46.12ab

2n

2n

nn

n

n

Ovary

Primordial germ cell

Mitotic divisions

Mitotic divisions

Oogonium

In embryo

Primary oocyte(present at birth), arrestedin prophase of meiosis I

Completion of meiosis Iand onset of meiosis II

Secondary oocyte,arrested at metaphase ofmeiosis II

Firstpolarbody

Ovulation, sperm entry

Completion of meiosis IISecondpolarbody

Primary oocytewithinfollicle

Growingfollicle

Mature follicle

Rupturedfollicle

Ovulatedsecondaryoocyte

Corpus luteum

Degeneratingcorpus luteum

Fertilized egg

Figure 46.12b

Figure 46.12bb

2n

2n

nn

n

n

Primordial germ cellMitotic divisions

Mitotic divisions

Oogonium

In embryo

Primary oocyte(present at birth), arrestedin prophase of meiosis I

Completion of meiosis Iand onset of meiosis II

Secondary oocyte,arrested at metaphase ofmeiosis II

Firstpolarbody

Ovulation, sperm entry

Completion of meiosis IISecondpolarbody

Fertilized egg

Stop Here and Do the Handout first

Hormones of Female Reproduction

Human reproduction is coordinated by hormones from the hypothalamus, anterior pituitary, and gonads

Gonadotropin-releasing hormone (GnRH) is secreted by the hypothalamus and directs the release of FSH and LH from the anterior pituitary

FSH and LH regulate processes in the gonads and the production of sex hormones

Concept 46.4: The interplay of tropic and sex hormones regulates mammalian reproduction

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In females, the secretion of hormones and the reproductive events they regulate are cyclic

Prior to ovulation, the endometrium thickens with blood vessels in preparation for embryo implantation

If an embryo does not implant in the endometrium, the endometrium is shed in a process called menstruation

Hormonal Control of the Female Reproductive Cycles

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Figure 46.13 Control by hypothalamus(a)

Hypothalamus

GnRH

Anterior pituitary

FSH LH

Inhibited by combination ofestradiol and progesterone

Stimulated by high levelsof estradiol

Inhibited by low levels ofestradiol

109

87

65

4

3

2

1

(b) Pituitary gonadotropinsin blood

LH

FSH

FSH and LH stimulatefollicle to grow

6

LH surge triggers ovulation

Ovarian cycle

Growing follicle Maturing follicle

Corpusluteum

Degeneratingcorpus luteum

Follicular phase Ovulation Luteal phase

Estradiol secretedby growing follicle inincreasing amounts

(c)

Progesterone andestradiol secretedby corpus luteum

(d) Ovarian hormonesin blood

Estradiol

Peak causes LH surge(see )

Progesterone

Progesterone and estra-diol promote thickeningof endometrium

Estradiol levelvery low

(e) Uterine (menstrual) cycle

Endometrium

Menstrual flow phase Proliferative phase Secretory phase

Day

s

28252015141050

Hypothalamus

GnRH

Anterior pituitary

FSH LH

Sertoli cells Leydig cells

Inhibin Spermatogenesis Testosterone

Testis

Neg

ativ

e fe

edb

ack

Neg

ativ

e fe

edb

ack

Figure 46.14

During its first 2 to 4 weeks, the embryo obtains nutrients directly from the endometrium

Meanwhile, the outer layer of the blastocyst, called the trophoblast, mingles with the endometrium and eventually forms the placenta

Blood from the embryo travels to the placenta through arteries of the umbilical cord and returns via the umbilical vein

Early Development

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Figure 46.16

Placenta

Uterus

Umbilicalcord

Chorionicvillus,containingfetalcapillaries

Maternalblood pool

Maternalarteries

Maternalveins

Maternalportion ofplacenta

Fetalportion ofplacenta(chorion)

Umbilicalarteries

Umbilical veinUmbilical cord

Fetal venuleFetal arteriole

Figure 46.18

Estradiol

from ovaries

Activates oxytocinreceptors on uterus

Oxytocin

from fetusand mother’s posterior pituitary

Prostaglandins

Po

siti

ve f

eed

bac

k

Stimulates uterusto contract

Stimulatesplacenta to make

Stimulate morecontractions

of uterus

Figure 46.19

Dilation of the cervix

2

1

3

PlacentaUmbilical cord

Uterus

Cervix

Expulsion: delivery of the infant

Delivery of the placenta

Uterus

Umbilical cord

Placenta (detaching)

DevelopmentThe importance of cell-cell communication.

Zygote

2-cellstageforming

4-cellstageforming

8-cellstage

Vegetal pole

Blastula(crosssection)

Gray crescent

Animalpole

Blastocoel

0.25 mm

0.25 mm

8-cell stage (viewedfrom the animal pole)

Blastula (at least 128 cells)

Figure 47.7

Gastrula Morula Blastula Zygote

In pairs write the following terms in order.

Terminology of Stages of DevelopmentZYGOTE

GASTRULA

BLASTULA (BLASTOCYST IN MAMMALS)

MORULA SOLID BALL

EMBRYO

After cleavage, the rate of cell division slows and the normal cell cycle is restored

Morphogenesis, the process by which cells occupy their appropriate locations, involves

◦ Gastrulation, the movement of cells from the blastula surface to the interior of the embryo

◦ Organogenesis, the formation of organs

Concept 47.2: Morphogenesis in animals involves specific changes in cell shape, position, and survival

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Gastrulation rearranges the cells of a blastula into a three-layered embryo, called a gastrula

Gastrulation

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The three layers produced by gastrulation are called embryonic germ layers

◦The ectoderm forms the outer layer ◦The mesoderm partly fills the space between the

endoderm and ectoderm◦The endoderm lines the digestive tract

Each germ layer contributes to specific structures in the adult animal

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ECTODERM (outer layer of embryo)

MESODERM (middle layer of embryo)

ENDODERM (inner layer of embryo)

• Epidermis of skin and its derivatives (including sweat glands, hair follicles)

• Epithelial lining of digestive tract and associated organs (liver, pancreas)• Epithelial lining of respiratory, excretory, and reproductive tracts and ducts

• Germ cells• Jaws and teeth• Pituitary gland, adrenal medulla• Nervous and sensory systems

• Skeletal and muscular systems• Circulatory and lymphatic systems• Excretory and reproductive systems (except germ cells)• Dermis of skin• Adrenal cortex

• Thymus, thyroid, and parathyroid glands

Figure 47.8

The four extraembryonic membranes that form around the embryo arise from the amniotic egg

◦ The chorion functions in gas exchange◦ The amnion encloses the amniotic fluid◦ The yolk sac encloses the yolk◦ The allantois disposes of waste products and

contributes to gas exchange

MEMBRANES

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During organogenesis, various regions of the germ layers develop into rudimentary organs

Early in vertebrate organogenesis, the notochord forms from mesoderm, and the neural plate forms from ectoderm

Organogenesis

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Figure 47.13

Neural folds

1 mm

Neural fold

Neural plate

Notochord

Ectoderm

Mesoderm

Endoderm

Archenteron

(a) Neural plate formation

(b) Neural tube formation

(c) Somites

Neural fold

Neural plate

Neural crest cells

Outer layerof ectoderm

Neural crest cells

Neural tube

Eye Somites Tail bud

SEM

Neural tube

Notochord

Coelom

Neuralcrestcells

Somite

Archenteron(digestivecavity)

1 mm

The neural plate soon curves inward, forming the neural tube

The neural tube will become the central nervous system (brain and spinal cord)

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Neural crest cells develop along the neural tube of vertebrates and form various parts of the embryo (nerves, parts of teeth, skull bones, and so on)

Mesoderm lateral to the notochord forms blocks called somites

Lateral to the somites, the mesoderm splits to form the coelom (body cavity)

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Figure 47.13c

(c) Somites

Eye Somites Tail bud

SEM

Neural tube

Notochord

Coelom

Neuralcrestcells

Somite

Archenteron(digestivecavity)

1 mm

The embryonic cells in a limb bud respond to positional information indicating location along three axes

◦Proximal-distal axis◦Anterior-posterior axis◦Dorsal-ventral axis

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(b) Wing of chick embryo

Digits

Anterior

Proximal

Dorsal

Posterior

Ventral

Distal

2

34

Figure 47.24b

Figure 47.25

Donorlimbbud

Hostlimbbud

ZPA

Anterior

Posterior

New ZPA

4

4

3

3

2 2

EXPERIMENT

RESULTS

What role does the zone of polarizing activity (ZPA) play in limb pattern formation in vertebrates?

Sonic hedgehog is an inductive signal for limb development

Hox genes also play roles during limb pattern formation

Read Cell Fate Determination and Pattern Formation 1039-1051

Cell Fate Determination

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Ciliary function is essential for proper specification of cell fate in the human embryo

Motile cilia play roles in left-right specification Monocilia (nonmotile cilia) play roles in normal

kidney development◦ Almost every cell has one that acts as a transporter and

an antenna to receive info from other cells

Cilia and Cell Fate

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Figure 47.26 Kartogener’s Syndrome

Lungs

Heart

Liver

Spleen

Stomach

Large intestine

Normal locationof internal organs

Location insitus inversus

EpididymisSeminiferous tubule

Testis

Cross section ofseminiferous tubule

Sertoli cellnucleus

Lumen ofseminiferous tubule

Plasmamembrane

Tail

Neck

Midpiece Head

Mitochondria

NucleusAcrosome

Primordial germ cell in embryo

Mitotic divisions

Spermatogonialstem cell

Spermatogonium

Mitotic divisions

Mitotic divisions

Primary spermatocyte

Meiosis I

Meiosis II

Spermatids (two stages)

Secondary spermatocyte

Earlyspermatid

Sperm cell

Differentiation(Sertoli cellsprovide nutrients)

2n

2n

2n

n n

n n n n

n n n n

Figure 46.12a

2n

2n

nn

n

n

Ovary

Primordial germ cell

Mitotic divisions

Mitotic divisions

Oogonium

In embryo

Primary oocyte(present at birth), arrestedin prophase of meiosis I

Completion of meiosis Iand onset of meiosis II

Secondary oocyte,arrested at metaphase ofmeiosis II

Firstpolarbody

Ovulation, sperm entry

Completion of meiosis IISecondpolarbody

Primary oocytewithinfollicle

Growingfollicle

Mature follicle

Rupturedfollicle

Ovulatedsecondaryoocyte

Corpus luteum

Degeneratingcorpus luteum

Fertilized egg

Figure 46.12b