Gametogenesis, Female cycle, and Embryonic development

Meiosis

specialized nuclear division that occurs in the testes to produce sperm, also occurs in the ovaries. end result is to produce haploid into diploid

Meiosis I and II

Two nuclear divisions of meiosis
-it reduces the chromosome number from 2n to n
-the chromatids are distributed equally to the daughter cells.

Homologous chromosomes

pairs of similar chromosomes in humans (23 pairs)

Diploid, Haploid

-(2n) chromosomes are paired in humans 2n=46 Chromosomes (23 pairs)
-(n) chromosomes are single n=23 single chromosomes.
Sperm+ Egg=Zygote
n+n=2n

Spermatogenesis

-the process of sperm formation; involves meiosis

Primary spermatocyte

-destined to produce four sperm (B in picture)

Secondary spermatocyte

- each primary spermatocyte generated during the first phase undergoes meiosis I forming two smaller haploid cells. (C in picture)

Spermatid

-daughters of secondary spermatocytes, are small rounded cells, with large spherical nuclei, seen closer to the lumen of the tubule (D in picture)

Sperm

(Spermatozoa)has a head a midpiece and a tail, which correspond roughly to genetic, metabolic, and locomotor regions respectively. (E in picture)

Spermiogenesis

-streamlining process in which it elongates, sheds its excess cytoplasmic baggage, and forms a tail (transformation of a Spermatid into a functional sperm)

development of flagella, shedding excess cytoplasm, develop enzymes called acrosomes

Spermiogenesis: steps of going from spermatid to sperm cell. (3)

Oogenesis

-process of ovum (female gamete) formation

Oogonium

Primary oocyte

(B in picture)

Secondary oocyte

(C in picture)

Polar bodies

small circle that is kind of on the side of the secondary follicle. on bigger model is the small white dot on top of the model.

ciliated epithelium of oviduct, muscle wall of oviduct

What helps move the egg? (2)

Fertilization

-fusion of the sperm and egg nuclei.

Zygote

Fertilized egg

Cleavage

-an early embryonic phase consisting of rapid mitotic cell
divisions
without intervening growth periods; product is a blastocyst.

Blastomeres

-two identical cells produced by the first cleavage division of the zygote (the lobes) 36 hours after fertilization.

Morula

-a loose collection of cells that form a berry shaped cluster of 16 or more cells, 72 hours after fertilization.

Blastocyst

-a fluid filled hollow sphere composed of a single layer of large flattened cells.

Inner cell mass

-a small cluster of 20 to 30 rounded cells inside the morula (yellow part)

Trophoblast

-single layer of large, flattened cells, produces HCG which becomes Chorion

Gastrulation

-developmental process that produces the three primary germ layers (ectoderm, mesoderm, endoderm)

Gastrula

-in which the three primary germ layers form, and the extraembryonic membranes develop.

Embryonic disc

-the subdivided inner cell mass divides amnion and yolk sac, is in the middle of both.

Primary germ layers

Ectoderm-embryonic germ layer; forms the epidermis of the skin and it's derivatives, and nervous tissue.
Mesoderm- primary germ layer that forms the skeleton and muscles of the body.
Endoderm- embryonic germ layer; forms the lining of the digestive tube a

Epidermis of skin, nervous tissue, sense organs, hair, nails, oil and sweat glands

What organs are made up of Ectoderm? 7

Skeletal system, circulatory system, dermis of skin, muscular system, reproductive system, excretory system, most connective tissue

What organs and systems are made of Mesoderm?
7

Digestive system, respiratory system, liver, pancreas, pharynx

What organs and systems are made of Endoderm? 5

Extraembryonic membranes

-form during the first two-three weeks of development include the amnion, yolk sac, allantois, and chorion

Chorion

-outermost fetal membrane;helps form the placenta. (blue part around) comes from thromphoblast, outermost of the membranes around embryo.

Chorionic villi

-fingerlike projections, become specially elaborate where they are in contact with maternal blood.

Amnion

grows around embryo, orange on our model, secretes amniotic fluid protects embryo

Yolk sac

yellow circle on our model, source of early blood cells and blood vessels and gives rise to GI tract

Allantois

Gives rise to urinary system, forms a small outpocketing of embryonic tissue at the caudal end of the yolk sac. the point in the yellow sac, structural base for umbilical cord

Umbilical cord

links embryo to the placenta

Placenta

-temporary organ formed from both fetal and maternal tissues that provides nutrients and oxygen to the developing fetus, carries away fetal metabolic wastes, and produces the hormones of pregnancy.