Animal Development

1
Animal Development

• Chapter 46 47

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Fig. 46-6
3
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

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Anatomy
5
Anatomy
Oviduct
Ovary
Uterus
(Urinary bladder)
(Pubic bone)
(Rectum)
Cervix
Urethra
Shaft
Vagina
Clitoris
Glans
Prepuce
Labia minora
Labia majora
Vaginal opening
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Fig. 46-10b
Oviduct
Ovaries
Follicles
Corpus luteum
Uterine wall
Uterus
Endometrium
Cervix
Vagina
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Female

• Ovaries (at birth)
• Contain approximately 1 million follicles
• Primary oocyte
• Started meiosis
• Stopped at prophase I (diploid)

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Female

• FSH
• Stimulates production of a follicle
• One follicle goes through Meiosis I
• Two daughter cells
• Secondary oocyte (starts Meiosis II)
• Polar body (disintegrates)

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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)

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Fig. 46-12g
In embryo
Primordial germ cell
Mitotic divisions
2n
Oogonium
Mitotic divisions
Primary oocyte(present at birth), arrestedin
prophase of meiosis I
2n
Completion of meiosis I and onset of meiosis II
Firstpolarbody
n
n
Secondary oocyte,arrested at metaphase of
meiosis II
Ovulation, sperm entry
Completion of meiosis II
Secondpolarbody
n
Fertilized egg
n
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Ovulation
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Menstrual cycle

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

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Menstrual cycle

• Corpus luteum releases progesterone estridiol
• Corpus luteum disintegrates
• Lining sheds
• Endometriosis
• Uterine lining in abdomen

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Menstrual cycle
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Anatomy
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Fig. 46-11b
(Urinarybladder)
(Urinaryduct)
Seminal vesicle
(Rectum)
(Pubic bone)
Vas deferens
Erectiletissue
Ejaculatory duct
Prostate gland
Urethra
Penis
Bulbourethral gland
Glans
Vas deferens
EpididymisTestisScrotum
Prepuce
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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

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Male

• Germ cells (diploid)
• Mitosis
• One undergoes meiosis
• Produce 4 haploid sperm
• Produce 100 to 200 million sperm a day
• Continues for life

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Spermatogenesis
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Fig. 46-12b
Epididymis
Seminiferous tubule
Sertoli cellnucleus
Spermatogonium
Primary spermatocyte
Testis
Cross sectionof seminiferoustubule
Secondary spermatocyte
Spermatids(two stages)
Sperm
Lumen ofseminiferous tubule
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Fig. 46-12c
Primordial germ cell in embryo
Mitotic divisions
Spermatogonialstem cell
2n
Mitotic divisions
Spermatogonium
2n
Mitotic divisions
Primary spermatocyte
2n
Meiosis I
Secondary spermatocyte
n
n
Meiosis II
Earlyspermatid
n
n
n
n
Differentiation (Sertolicells provide nutrients)
Sperm
n
n
n
n
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Gamete formation
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Embryonic development

• Fertilization
• Cleavage
• Gastrulation
• Neurulation
• Organogenesis

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Fertilization

• 1. Penetration
• Sperm digests cells surrounding egg
• Contains glycoprotein enzymes
• 2. Activation
• Membrane changes
• Prevents other sperm penetrating

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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

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Fertilization

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

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Fertilization
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Cleavage

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

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Fig. 47-6
(a) Fertilized egg
(b) Four-cell stage
(c) Early blastula
(d) Later blastula
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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

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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

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Fig. 47-8-6
0.25 mm
0.25 mm
Animal pole
Blastocoel
Vegetalpole
Zygote
2-cellstageforming
Blastula(crosssection)
4-cellstageforming
8-cellstage
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Cleavage

• Implantation
• Blastocyst attaches to endometrium
• 6 days after fertilization
• Human chorionic gonadotropin (HCG)
• Hormone released by trophoblast
• Maintains corpus luteum

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Fig. 47-16-2
Expandingregion oftrophoblast
Maternalbloodvessel
Epiblast
Hypoblast
Trophoblast
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Gastrulation

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

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Fig. 47-14
ECTODERM
MESODERM
ENDODERM
NotochordSkeletal systemMuscular
systemMuscular layer ofstomach and
intestineExcretory systemCirculatory and
lymphaticsystems Reproductive system(except
germ cells) Dermis of skinLining of body
cavityAdrenal cortex
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
Epithelial lining ofdigestive tractEpithelial
lining ofrespiratory systemLining of urethra,
urinarybladder, and reproductivesystemLiverPan
creasThymusThyroid and parathyroidglands
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Gastrulation
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Gastrulation

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

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Gastrulation
Amnion
Chorion
Ectoderm
Mesoderm
Endoderm
Yolk sac
Extraembryonicmesoderm
Atlantois
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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

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Neural cord
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Neurulation

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

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Fig. 47-12b-4
Outer layerof ectoderm
Neural crestcells
Neural tube
(b) Neural tube formation
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Organogenesis

• Below neural tube
• Somitomeres
• Small sections of mesoderm
• Somites
• Smaller sections of mesoderm
• Develop into muscles, vertebrae, connective
  tissues

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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

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Human development

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

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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

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Fig. 46-17a
(a) 5 weeks
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Human development

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

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Fig. 46-17b
(b) 14 weeks
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Fig. 46-17c
(c) 20 weeks
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Human development

• Third trimester
• Large growth of fetus
• Developing nerves

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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

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Fig. 46-18
Oxytocin
Estradiol

fromovaries
from fetusand mothersposterior pituitary
Induces oxytocinreceptors on uterus
Positive feedback
Stimulates uterusto contract
Stimulates placenta to make

Prostaglandins
Stimulate morecontractionsof uterus
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Fig. 46-19-2
Expulsion delivery of the infant
2
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Fig. 46-19-3
Uterus
Placenta (detaching)
Umbilical cord
Delivery of the placenta
3
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Placenta

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Fig. 46-16
Maternalarteries
Maternalveins
Placenta
Maternalportionof placenta
Umbilical cord
Chorionic villus,containing fetalcapillaries
Fetalportion ofplacenta(chorion)
Maternal bloodpools
Uterus
Umbilicalarteries
Fetal arteriole
Fetal venule
Umbilicalvein
Umbilical cord
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