1. Early development
i. Ectoderm : all nervous tissue, skin, eyes, ears, hair, feathers, pituitary gland, adrenal medulla.
ii. Endoderm: linings of digestive, respiratory, reproductive tracts.
iii. Mesoderm: muscle, bone, blood, kidney and gonads.
2. Control of Development
4. Frog Development
5. Chicken Development
7. Human Development
i. During the first few days the zygote undergoes repeated cleavages as it travels down the oviduct.
ii. By the time it reaches the uterus( 5 days), it is a solid ballof cells called a morula which is transformed into a blastocyst
iii. Before the first week ends, the balstocyst contacts and adheres to the uterine lining and is tranformed into an embyonic disk that will develop into the embryo proper within the next week.
iv. Implants in uterus at blastocyst stage.
v. The trophoblast is the embryonic membrane.
vi. The embryo is called the inner cell mass.
vii. Around the embryo and part of the placenta is the Chorionic villi.
viii. The placenta is the place of exchange of wastes and nutrients.
ix. Embryo is smaller than a pea at one month.
x. By the third week many organ systems have begun to form including the nervous system, heart, blood vessels, esphagus, stomach, liver, panceas and intestines.
xi. All the major organ systems are formed at 2 months and will merely increase in size for the remainder of the pregnancy.
xii. Heart pulses at 3-4 weeks.
xiii. Buds appear for arms and legs
xiv. 1st 6 weeks crucial for normal development.
i. yolk sac gives rise to the digestive tube
ii. the allantois does not function in waste storage as in bird eggs but is active in oxygen transport
iii. The amnion is a fluid filled sac that keeps the embryo from drying out and acts as a shock absorber.
iv. The chorion is a protective membrane around the embryo and forms a portion of the placenta It secretes a hormone that maintains the uterine lining after implantation.
v. The umbilical cord connects the growing embryo to parts of the yolk sac, allantois and chorion.
vi. The placenta (formed at about day 17) is a combination of endometrial tissue and embryonic chorion.
vii. Materials are exchanged from the blood capillaries of mother to fetus and vice versa by diffusion. The maternal blood and the fetal blood do not mix.
H. Miscarriage is loss of embryo or fetus before 20 weeks. Occurs in more than 30 % of pregnancies (50%?). Most occur before 12 weeks. 50-60 % due to chromosomal damage so severe that the fetus would not develop anyways.
i. Sensitive to light
ii. Movements felt by mother.
iii. Moves at 4 months and some body systems start to function.
iv. Embryo now called a fetus will undergo a major increase in size (600 x).
i. Finishing touches
ii. Mother is uncomfortable
i. uterus grows to contain more than 5 liters, enlarges 500-1000x.
ii. Ovaries less active, secrete relaxin, a hormone that relaxes ligaments.
iii. Skin changes in pigment, mask of pregnancy, dark line on abdomen, increased oil production on face, vacular spiders.
iv. Blood volume increased by more than 50 %.
v. Urinary system , kidneys filter 50-60 % more urine.
vi. Heartburn, bloating, constipation, bums enlarge and bleed, hemorrhoids.
i. Lightening is when fetal head drops into womanís pelvis. A couple of weeks before labor.
ii. Braxton-Hicks contractions (false labor)
iii. Passing of mucus plug occurs up to 2 weeks before birth.
iv. Contractions are caused by oxytocin.
v. Early labor can last minute-days. Cervix is less than 4 cm dilated.
vi. Stage one: active labor 4-10 cm dilated. Contractions are 3-5 minutes apart.
vii. Transition: 7-10 cm dilated. Contractions one right on top of the other.
viii. Stage Two: Pushing, 1-2 hours
ix. Stage three; expulsion of placenta.
i. Breast milk contains lipase, an enzyme that breaks down fats.
ii. 300 components in breast milk.
i. The composition of breast milk changes in the am vs. pm.
ii. The composition of breast milk changes between the 1st month and the 7th. Goes from whole milk to lowfat.
iii. The fat composition changes during a feeding. 1st milk is lowfat, the longer the infant nurses the more fat is added to the milk.
iv. Increasing the number of feeding increases the fat content of the milk.
i. Breast milk contains essential fats that are parts of the myelin sheath( insulation on nerve cells). If the mom does not eat the correct fats, the breast will make these fats.
ii. There is a lot of cholesterol in human milk, little in cows milk and none in formula. Cholesterol is needed in brain development.
iii. Human milk has more lactose than any other mammalian milk. The more lactose in the milk the larger the mammals brain is.