PQ_B100-Chp38.ppt 1910KB Mar 29 2010 04:55:26 AM

(1)

Animal Reproduction and

Development

(2)

Modes of Reproduction

• _{Sexual reproduction}

– _{Meiosis, gamete formation, and}

fertilization

– _{Offspring show genetic variation}

• _{Asexual reproduction}

(3)

Stages of Development

Gamete formation

Fertilization

Cleavage

Gastrulation

Organ formation

(4)

Development Overview

frog egg

frog sperm

midsectional views Eggs form and mature in female

reproductive organs, and sperm form and mature in male

reproductive organs.

A sperm and an egg fuse at their plasma membrane, then the nucleus of one fuses with the nucleus of the other to form the zygote.

By a series of mitotic cell divisions, different daughter cells receive different regions of the egg cytoplasm.

Cell divisions, migrations, and rearrangements produce two or three primary tissues, the

forerunners of specialized tissues and organs.

Subpopulations of cells are sculpted into specialized organs and tissues in prescribed spatial

Gamete formation

Fertilization

Cleavage

Gastrulation

(5)

Male

seminal vesicle

prostate gland

bulbourethral gland

urethra bladder

(6)

Spermatogenesis

• _{Spermatogonium (2n) divides by}

mitosis to form primary spermatocyte (2n)

(7)

Testicular Cells

• Sertoli cells

– Line the seminiferous tubules

– Nourish the developing sperm

• _{Leydig cells}

– _{Lie between the seminiferous} tubules

(8)

Female Reproductive Organs

oviduct

vagina uterus ovary

cervix vagina

uterus

(9)

Menstrual Cycle

• The fertile period for a human female occurs on a cyclic

basis

• _{Menstrual cycle lasts about 28}

(10)

Fertilization

• Sperm penetrates to egg cytoplasm

(11)

Pregnancy

• _{Averages 38 weeks from fertilization} • _{Takes two weeks for blastocyst to}

form

(12)

Early Divisions

• Cleavage begins within 24 hours of fertilization

Day 1 _{Day 2} _{Day 3} Day 4

(13)

Day 5 -

Blastocyst Forms

• Cell secretions produce a fluid-filled cavity in center of ball of cells

• Layers of blastocyst

– _{Inner cell mass} – Trophoblast

– _Blastocoel

inner cell mass

(14)

Implantation Begins

• Blastocyst attaches to endometrium (UTERUS) ;

begins to burrow into maternal

blastocoel

inner cell

(15)

Extraembryonic Membranes

DAY 14

yolk sac

chorionic cavity chorionic

villi

chorion

amniotic cavity

connecting stalk

• _{The amniotic}

membrane will enclose embryo

• Yolk sac forms

• _{Chorion begins to}

(16)

Human Chorionic

Gonadotropin (HCG)

• Hormone secreted by the blastocyst

• _{Stimulates corpus luteum to keep} making progesterone and estrogens

• This maintains endometrium, prevents menstruation

(17)

Gastrulation - Day 15

• _{Primitive streak}

forms along one axis of the inner cell mass

• _{Cells migrate}

inward here to form endoderm and

(18)

Gastrulation

• Sphere of cells is a blastula

• _During

gastrulation, some cells move inward

• _{Produces a}

(19)

Vertebrate Body Plan Emerges

paired neural folds

somites

(20)

The Placenta

• _{Interlocking fetal and maternal}

tissues

• Performs digestive, respiratory, and urinary functions for the

fetus

• Materials exchanged across

4 weeks

8 weeks

(21)

Embryonic Period

• Weeks 3 to 8

• _{By the close of embryo}

period

– Appears human

Week 4

(22)

Fetal Period

• Weeks 9 to birth

• _{Fetus is initially about 1 inch long}

• _{Fetus born before 22 weeks cannot}

survive

(23)

Fetal Nutrition

• _{All nutrients for fetal growth and}

development must be delivered via the placenta

• _{Mother’s diet affects fetal health}

• _{Smoking may affect ability to absorb}

(24)

Birth (Labor)

• _{Cervical canal dilates}

• _{Amniotic sac ruptures}

• Uterine contractions drive fetus from uterus

• _{Placenta is expelled as}

(25)

Lactation

• _{During pregnancy, progesterone}

and estrogen stimulate gland development

• _{After birth, prolactin induces}

synthesis of enzymes for milk production

(26)

Stages of Human

Development - Prenatal

• Zygote - Single cell

• Morula - Solid ball of cells

• Blastocyst - Ball with fluid-filled cavity

• Embryo - 2 weeks to 8 weeks

(27)

Stages of

Human

Development -

Postnatal

• Newborn - First 2 weeks after birth

• _{Infant -}_{2 weeks to 15} months

• Child - 10-12 years

• Pubescent - At puberty • Adolescent - Puberty

to maturation • _Adult

(28)

Birth Control Options

Prevent fertilization

Prevent ovulation

(29)

Sexually Transmitted

Diseases (STDs)

• _{Worldwide epidemic of STDs}

• _{Women are most affected}

• _{Can cause infertility, pain,}

(30)

Causative Agents of STDs

• Viruses

– AIDS (HIV)

– Genital herpes

(Herpes simplex)

– _{Genital warts}

(HPV)

• Bacteria

– Gonorrhea

(Neisseria

gonorrhoeae)

– _Syphilis

(Trepnema pallidum)

– Chlamydial

(31)

In Vitro Fertilization

• Conception outside the body

• _{Woman receives hormone injections to} stimulate ovulation

• Oocyte is removed and combined with sperm in petri dish

(32)

Abortion

• _{Removal of blastocyst, embryo, or}

fetus

• _{First trimester abortions are painless,}

and relatively complication free

• _{Later abortions are more difficult and}