Animal Development

Chapter 46 & 47

Fig. 46-6

Vocabulary Zygote: Single diploid cell Fertilization: Sperm & egg combine Ovulation: Egg is released from the ovary Spermatogenesis: Formation of sperm Oogenesis: Formation of the egg

Anatomy

Anatomy

(Rectum)

Cervix

Vagina

Vaginal opening

Oviduct

Ovary

Uterus

(Urinary bladder)

(Pubic bone)

Urethra

ClitorisShaftGlansPrepuce

Labia minora

Labia majora

Fig. 46-10b

OvariesOviduct

FolliclesCorpus luteum

Uterine wallUterus

Cervix

Endometrium

Vagina

Female

Ovaries (at birth) Contain approximately 1 million

follicles Primary oocyte Started meiosis Stopped at prophase I (diploid)

Female

FSH Stimulates production of a follicle One follicle goes through Meiosis I Two daughter cells Secondary oocyte (starts Meiosis

II) Polar body (disintegrates)

Female

LH stimulates ovary Secondary oocyte leaves ovary Ovulation Fertilized then completes Meiosis II Ovum Polar body Travels fallopian tube Implants in uterus (approx. 5-6 days)

Fig. 46-12gPrimordial germ cell

Mitotic divisions

Oogonium

Mitotic divisions

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

Completion of meiosis I and onset of meiosis II

Secondary oocyte,arrested at metaphase of meiosis II

Firstpolarbody

Ovulation, sperm entry

Completion of meiosis IISecondpolarbody

Fertilized egg

2n

2n

nn

n

n

In embryo

Ovulation

Menstrual cycle

GnRH FSH & LH released Stimulates follicle Estradiol released Follicle released (ovulation) LH increases

Menstrual cycle

Corpus luteum releases progesterone & estridiol

Corpus luteum disintegrates Lining sheds Endometriosis: Uterine lining in abdomen

Menstrual cycle

Anatomy

Fig. 46-11b

Seminal vesicle

(Rectum)

Vas deferens

Ejaculatory duct

Prostate gland

Bulbourethral gland

Vas deferens EpididymisTestisScrotum

(Urinarybladder)

(Urinaryduct)

(Pubic bone)

Erectiletissue

Urethra

Glans

Prepuce

Penis

Male

Testes are in abdomen (at birth) Descend into scrotum Temperature of testes is cooler Normal sperm production Seminiferous tubules Contain spermatogonia or germ

cells

Male

Germ cells (diploid) Mitosis One undergoes meiosis Produce 4 haploid sperm Produce 100 to 200 million sperm

a day Continues for life

Spermatogenesis

Fig. 46-12b

Epididymis

Seminiferous tubuleSertoli cellnucleus

Testis

Cross sectionof seminiferoustubule

Spermatogonium

Primary spermatocyte

Secondary spermatocyte

Spermatids(two stages)

SpermLumen ofseminiferous tubule

Fig. 46-12c Primordial germ cell in embryo

Mitotic divisions

Spermatogonialstem cell

Mitotic divisions

Spermatogonium

Mitotic divisions

Primary spermatocyte

Meiosis I

Secondary spermatocyte

Meiosis II

Earlyspermatid

Differentiation (Sertolicells provide nutrients)

Sperm

2n

2n

2n

n n

n n n n

n n n n

Gamete formation

Embryonic development

Fertilization Cleavage Gastrulation Neurulation Organogenesis

Fertilization

1. Penetration Sperm digests cells surrounding

egg Contains glycoprotein enzymes 2. Activation Membrane changes Prevents other sperm penetrating

Fertilization

2. Activation A. stimulates egg to complete

division of Meiosis II B. stimulates movement of

cytoplasm to prepare for cell division of zygote

C. stimulates increase in protein synthesis

Fertilization

3. Nuclei fusion Sperm nucleus fuses with egg Egg is not activated Does not form zygote

Fertilization

Cleavage

Rapid cell division Blastomeres: Smaller & smaller cells No increase in volume of cytoplasm Morula: Tight mass of approximately 32 cells

Fig. 47-6

(a) Fertilized egg (b) Four-cell stage (c) Early blastula (d) Later blastula

Cleavage

Blastocyst (Blastula) Hollow ball of approx. 500-2000 cells Blastocyst cavity Fluid filled Different regions in blastocyst Received differing amounts of

cytoplasm Affects further development

Cleavage

Trophoblast: Outer layer of cells Surround blastocyst (involved in

placenta) Inner cell mass: Layer of dividing cells At one end of Blastocyst Becomes developing embryo

Fig. 47-8-6

Blastula(crosssection)

BlastocoelAnimal pole

4-cellstageforming

2-cellstageforming

Zygote 8-cellstage

Vegetalpole

0.25 mm 0.25 mm

Cleavage

Implantation: Blastocyst attaches to endometrium 6 days after fertilization Human chorionic gonadotropin

(HCG) Hormone released by trophoblast Maintains corpus luteum

Fig. 47-16-2

Trophoblast

Hypoblast

Maternalbloodvessel

Expandingregion oftrophoblast

Epiblast

Gastrulation

Turning inward of cells into blastocyst Forms germ layers Ectoderm: Epidermis/neural tissue Mesoderm: Muscle/skeletal/vasculature Endoderm: Gut lining, respiratory tract, liver

Fig. 47-14

ECTODERM MESODERM ENDODERM

Epidermis of skin and itsderivatives (including sweatglands, hair follicles)Epithelial lining of mouthand anusCornea and lens of eyeNervous systemSensory receptors inepidermisAdrenal medullaTooth enamelEpithelium of pineal andpituitary glands

NotochordSkeletal systemMuscular systemMuscular layer ofstomach and intestineExcretory systemCirculatory and lymphaticsystemsReproductive system(except germ cells)Dermis of skinLining of body cavityAdrenal cortex

Epithelial lining ofdigestive tractEpithelial lining ofrespiratory systemLining of urethra, urinarybladder, and reproductivesystemLiverPancreasThymusThyroid and parathyroidglands

Gastrulation

Gastrulation

Chorion: Surrounds embryo Gas exchange Amnion: Encloses the embryo Protective amniotic fluid Yolk sac: Formation of blood cells

Gastrulation

Yolk sac

Mesoderm

Amnion

Chorion

Ectoderm

Extraembryonicmesoderm

Atlantois

Endoderm

Neurulation

Development of dorsal nerve cord Notochord (spinal column) Forms from mesoderm soon after

gastrulation Neural grove (spinal cord/brain) Crease down the axis of the embryo Neural tube (ectoderm) Hollow cylinder

Neural cord

Neurulation

Neural crest Cells pinch off from neural tube Migrate to parts of embryo Peripheral nerves, teeth, skull bones

Fig. 47-12b-4

Neural tube

Neural crestcells

Outer layerof ectoderm

(b) Neural tube formation

Organogenesis

Below neural tube Somitomeres: Small sections of mesoderm Somites Smaller sections of mesoderm Develop into muscles, vertebrae,

connective tissues

Organogenesis

Mesoderm surrounds the endoderm

Separates into 2 layers One lines the inner body wall One lines the outside of the gut Between layers becomes body

cavity

Human development

266 days divided into trimesters First trimester First cleavage 30 hours Second cleavage 60 hours Third cleavage 72 hours

Human development

Gastrulation second week Neurulation third week Organogenesis Heart beats at 4 weeks (heard at end of

first trimester) Fetus at 8 weeks All major organs are developed 5 cm in length

Fig. 46-17a

(a) 5 weeks

Human development

Second trimester Large growth Baby about 30 cm in length Lanugo: fine hair covering body Placenta now controls

progesterone levels

Fig. 46-17b

(b) 14 weeks

Fig. 46-17c

(c) 20 weeks

Human development

Third trimester Large growth of fetus Developing nerves

Human development

Birth Labor Estrogen stimulates the production

of oxytocin receptors on the uterus Prostaglandins start labor Posterior pituitary releases oxytocin Uterine contractions expel fetus

Fig. 46-18Estradiol Oxytocin

fromovaries

Induces oxytocinreceptors on uterus

from fetusand mother’sposterior pituitary

Stimulates uterusto contract

Stimulates placenta to make

Prostaglandins

Stimulate morecontractions

of uterus

Po

siti

ve

fee

db

ac

k

+

+

Fig. 46-19-2

Expulsion: delivery of the infant2

Fig. 46-19-3

Delivery of the placenta

Uterus

Placenta(detaching)

Umbilicalcord

3

Placenta

Fig. 46-16

Placenta

Uterus

Umbilical cord

Chorionic villus,containing fetalcapillaries

Maternal bloodpools

Maternalarteries

Maternalveins

Maternalportionof placenta

Fetal arterioleFetal venuleUmbilical cord

Fetalportion ofplacenta(chorion)

Umbilicalarteries

Umbilicalvein