23 - Pregnancy, Growth and Dev

full-term

266 days

Life expectancy

75.4 for men; 83.2 for women

meiosis II

Cell division that occurs immediately upon penetration of the oocyte

embryonic stage

Most critical period. Stage that extends from the beginning of the 2nd week through the eighth week of prenatal development. Placenta forms, the main internal organs develop, and the major external body structures appear.

zygote

The first cell resulting from union of sperm and oocyte chromosomes

ligamentum arteriosum

a cord that represents the ductus arteriosus.

fossa ovalis

a depression that marks the size of the past foramen ovale

blastocyst

a hollow ball of cells formed after division of the morula. This drops into one of the tubules in the endometrium. Its inner cell mass cell gives rise to the embryo proper (the body of the developing offspring).

amnion

a second membrane that develops around the embryo. It appears during the 2nd week. Filled with amniotic fluid

gastrula

after the primary germ layers form, the embryo is termed this. It is when the connecting stalk appears

connecting stalk

attaches the embryo to the developing placenta

3 days

average number of days between fertilization and arrival at the lumen of the uterus

Childhood

begins at end of first year and ends at puberty

inner cell mass

blastocyst cells in one region group to form this, and it gives rise to the embryo proper

trophoblast

cells that form the wall of the blastocyst, and develop into structures that assist the embryo

placenta

develops from the disc-shaped area where the chorion are still contacting the uterine wall

fetal stage

end of 8th week until birth. Growth is rapid and body proportions change considerably. Head is larger in the beginning and lower limbs are short.

primary germ layers of the primordial embryo

endoderm mesoderm ectoderm

cilia

epithelial cell membrane features that aid in moving an embyro (cells) through the fallopian tube

amniotic fluid

fills the space between the amnion and the embryonic disc. Provides a watery environment in which the embryo can grow freely without being compressed by surrounding tissues. Also protects the embryo from being jarred by mother's movements. Also maintains a stable temperature for proper embryonic and fetal development

mesoderm

forms between the ectoderm and endoderm later after a process called gastrulation. Responsible for the muscle tissue, bone tissue, bone marrow, blood, blood vessels, lymphatic vessels, internal reproductive organs, kidneys and mesolitheum of the body cavities.

yolk sac

forms during the 2nd week. Attached to the underside of the embryonic disc. Forms blood cells in the early stages of dev. and gives rise to the cells that later become sex cells.

allantois

forms during the 3rd week as a tube extending from the early yolk sac into the connecting stalk of the embryo. Forms blood cells and gives rise to umbilical arteries and vein. Forms umbilical blood vessels

umbilical cord

forms from the connecting stalk and the amnion. Contains 3 blood vessels (2 arteries and one vein) that communicate between the embryo and the placenta.

Infancy period

from 4 weeks to one year. Grows rapidly and may triple its birth weight. Teeth begin to erupt, and muscular and nervous systems mature so coordinated muscular activities become possible.

neonatal period

from birth to the end of the first four weeks

prolactin

hormone released by the anterior pituitary gland that stimulates milk production

oxytocin

hormone released by the posterior pituitary gland that stimulates secretion of milk

neonate's first breath is stimulated by

increased concentration of CO2 decreased pH low O2 concentration drop in body temperature mechanical stimulation during and after birth

lacunae

irregular spaces in the endometrium around and between the chorionic villi. Fill with maternal blood.

glandular tissue

mammary adipose changes to this type of tissue during pregnancy - promoted by placental estrogens and progesterone.

placental membrane

membrane separating the embyronic blood from maternal blood. Composed of epithelium of the chorionic villus and the endothelium of the capillary inside the villus. Through this membrane, substances are exchanged b/w the maternal blood and embryo's blood. Uses mostly diffusion for exchanges, but also includes active transport and pinocytosis to move substances through.

ductus arteriosus

most of the blood in the pulmonary trunk bypasses the lungs by entering this fetal vessel which connects the pulmonary trunk to the decending portion of the aortic arch. Passage allowing blood from right ventricle to enter aorta leaving the fetal heart. Later becomes the ligamentum arteriosum

foramen ovale

opening of the heart that the fetal blood moves from the right atrium to the left atrium. Later becomes the fossa ovalis.

adolescence

period of development from puberty to adulthood

mitosis

process by which the cell resulting from fertilization divides.

Senescence

process of growing old. Body becomes less able to cope with demands placed on it. Normal wear-and-tear. Cartilage may wear away leaving joints stiff and painful; blood circulation may be interefered with by diseases; metabolic rate and body fluids may change; decreasing efficiency of the CNS. Sensory functions decline with age, too.

cleavage

rapid cell division and distribution of the zygote's cytoplasm into progressively smaller cells - yields smaller and smaller cells

surfactant

reduces surface tension of the pleural membranes

posterior pituitary gland

secretes oxytocin

chorionic villi

slender projections from the trophoblast. Cover the entire surface of the trophoblast until the end of the 8th week.

morula

solid ball of approximately 16 cells. It remains free in the uterine cavity for about 3 days. Cell division continues. Gives rise to the blastocyst.

zona pellucida

sperm bind to this structure that surrounds the oocyte cell membrane. When the sperm that enters the 2ndary oocyte leaves its middle section and tail outside, lysosome-like vesicles beneath the oocyte cell membrane release enzymes that harden this structure, reducing the chance that other sperm cells will penetrate.

oxytocin

stimulates powerful uterine smooth muscle contractions.

yolk sac and allantois

structures that form blood cells for the developing embryo/fetus

umbilical arteries

term for 2 of the 3 blood vessels in the umbilical cord

fetus

term for a developing human from eight weeks post-conception until birth

embryo

term for a developing human from two until 8 weeks post-conception

30

the age that seems to be a developmental turning point. Hearing often becomes less acute; heart muscle begins to thicken; elasticity of the ligaments between the small bones in the back lessens. Body will then become functionally less efficient by about .8% every year.

embryo proper

the body of the developing offspring.

acrosome

the head of the sperm. Contains enzymes that enable sperm to penetrate the zona pellucida

120 years

the human life span - length of time that a human can THEORETICALLY live.

endoderm

the inner germ layer of the embryonic disc. responsible for epithelial cells of the digestive tract, respiratory tracts, urinary bladder and urethra.

implantation

the nestling of the blastocyst into the uterine lining

ectoderm

the superficial germ layer of the embryonic disc. responsible for the CNS, parts of the sensory organs, the epidermis, hair nails, glands of skin and linings of mouth and anal canal.

chorion

the trophoblast and a second layer of cells that line the trophoblast

positive feedback

uterine contractions stimulate even stronger contractions by way of this regulatory process. The stretch of the cervix elicits a reflex that stimulates stronger labor contractions.

placenta

vascular structure formed by cells surrounding the embryo and cells of the endometrium. It attaches the embryo to the uterine wall and exchanges nutrients, gases, and wastes between the maternal blood and the embryo's blood.

puberty

when childhood ends