Embryonic Differentiation & Development

Path of the sperm & egg to fertilization & implantation Produced in semeniferous tubules of the testes Move to epididymis for maturing Through the vas deferens Out the urethra Into the vagina Through the cervix Through the uterus Into oviduct Egg: Produced in follicle of the ovary Released into the oviduct Fertilization: occurs in the oviduct. Implantation: occurs in the endometrium of the uterus after the zygote travels down the oviduct

Identical vs. Fraternal twins Identical twins arise from 1 egg/sperm combination & during cleavage the zygote splits into two producing two zygotes with identical DNA Fraternal twins arise when two eggs are fertilized but two separate sperm.

Identical vs. Fraternal twins If a lady has quintuplets what possible combinations of fraternal & identical are there?

Basic Stages of embryonic development 1) morula 2) Blastocyst 3) Gastrula 4) Neurula

Basic Stages of embryonic development Morula: mass of identical cells resulting from cleavage. Each cells become smaller and size of the ball does not increase Blastocyst: as cleavage continues the ball of cells becomes hollow and contains an inner mass of cells Gastrula: When cells begin to specialize and form germ layers. Neurula: As Gastrula develops it forms a neural tube

Basic Stages of embryonic development other definitions p. 507-508 Cleavage: cell division without growth Trophoblast: outer layer of cells around the blastocyst which will form the placenta & Umbilical cord Embryo: time from cleavage starts until bone forms. Germ layers: three layers in gastrula endoderm, Mesoderm, ectoderm

Primary membranes of embryonic development

Primary membranes of embryonic development p. 508 Chorion: involved in gas exchange Amnion: contains the amniotic fluid Allantois: collects waste Yolk: provides nutrients

Placenta & Umbilical Cord p. 510 Umbilical cord connects the fetus to the placenta via arteries and veins allowing waste out to mothers blood and receiving nutrients from mothers blood Placenta: forms from the chorion. Blood vessel rich organ with branches that project into the uterine wall.(chorionic villi) Maternal blood and fetus blood never mixes. Nutrients are passed by diffusion

Cigarette smoke, alcohol and thalidomide are all known teratogens Teratogens p. 511 Teratogens: any substance that causes a physical abnormality in the development of the fetus Cigarette smoke, alcohol and thalidomide are all known teratogens Cigarette smoke constriction of blood vessels, low body weight and convulsions Alcohol causes (FAS) decreased weight, height and head size, mental retardation & agression Thalidomide was given to pregnant women to reduce morning sickness but it caused missing and deformed limbs

Child Birth in Humans p. 512-513

Child Birth in Humans p. 512-513 Dilation Stage: uterine contractions and oxytocin cause cervix to dilate. Amniotic sac breaks Expulsion stage: forceful uterine contractions force baby through the birth canal Placental Stage: placenta and umbilical cord are expelled 10-15 minutes after the baby and is known as “after birth”.

Hormones after birth p. 513-514 Estrogen & progesterone were high during pregnancy and inhibited prolactin production. After birth estrogen and progesterone decrease allowing prolactin to be produced. Prolactin is produced by the anterior pituitary and stimulates mammary glands to produce milk. Suckling is detected by anterioir pituitary which produces oxytocin. Oxytocin causes contraction of the mammary gland to force milk out the mamary duct

Fertilization in Flowers p. 175

Fertilization in Flowers p. 175 Pollen grain contains a tube nucleus & generative nucleus. Tube nucleus digs the pollen tube down to the micropyle (hole in the ovule). Generative nucleus forms 2 sperm nuclei. One fertilizes the egg forming the embryo. The other joins with 2 haploid nuclie to form the 3n endosperm (food source for the seed.

Monocot seeds vs. dicot seeds p. 175 Monocot seeds have one seed leaf while dicot seeds have two seed leaves