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