51.4 Pregnancy and Birth in Mammals

51.4 Pregnancy and Birth in Mammals

• Three types of pregnancies are found in mammals, which correspond embryo or fetus grows within the uterus of the mother.
• When rians, eutherians, and metathe cally are included, it is considered to begin not at fertilization but when they are pregnant.
• The embryo is in the uterus.
• The platypus is the only mammal that can lay fertilized days of fertilization in animals that have short lifespans.
• The young are born in large animals and take weeks to mature.

• Maternal length varies widely and is related to her pouch, where they attach to a nipple to suckle and obtain nour to the size of adults in a particular species.
• There are small animals within the pouch.
• Humans and other eutherian mammals have a longer period of time in the uterus and can give birth to more than one child at a time.

• The embryo and the mother are more developed at birth.

• Maternal and fetal tissues make up the placenta in mammals.
• The relationship between fetal and maternal structures can be seen in theEnlarged view of the placenta.
• Fetal and maternal blood does not mix in humans.
• The direction of blood flow is indicated by the black and white arrows.

• The blue and red colors of the arteries signify that they carry deoxygenated blood, and the vein is red to signify that it carries oxygenated blood.
• Normally, arteries and veins carry oxygenated blood, but they don't carry deoxygenated blood in the pulmonary circulation.

• There is a maternal portion and a fetal portion.

• The mother's blood vessels are rich in blood vessels from the fetus.
• The maternal and fetal vessels are close together.

• A lower P indicates a higher affinity of hemoglobin for oxygen.

• The values are for humans.

• From the maternal blood comes suites that diffuse into fetal capillaries and then into the fetal vein.
• Carbon genes are only expressed during certain stages of embryonic dioxide and other waste products from the fetus are carried through development.
• The oxygen er's circulation is important in mammals because they excrete it in the placenta.
• Fetal and maternal blood do not mix because of the different demands of the embryo and fetus.

• The differential expression of hemoglobin genes during the third and fourth trimesters of fetal development in humans lasts about 3 months.

• The major subunits in hemoglobin are found in the second trimester.
• When the fetus makes the transition to breathing air, the e-globin and Z-globin genes are turned on.

• The higher affinities of embryonic and fetal hemo globins allow the embryo and fetus to remove oxygen from the bloodstream and use it to create gene families.
• Families with genes have had their own demands.
• The evolution of different important in the evolution of complex traits because the vari globin genes each of which is expressed at particular stages of members of a gene family enable the expression of complex, of development enables placental mammals to develop in the specialized forms and functions.
• The uterus is not breathing on its own or being exposed to the globin gene family in animals.

• Oxygen is delivered to all of the body's cells by Hemoglobin, which is present in erythrocytes.

• Hor tend to have specialized functions at the end of pregnancies.
• Estradiol enters the maternal circulation when certain globin mones from the fetus are stimulated.

• The mother's hypothalamus sends stimulatory signals to the stretch sensitive sensory neurons that the fetus' head pushes against.

• The sensory nerves are stimulated by the hypothalamus.

• Stronger uterus contractions can be stimulated by the drug roxtocin.

• Prostaglandins are produced by the uterus.
• Sensory input to the hypothalamus continues to be enhanced by stronger contractions.

• Neural signals from the uterus and maternal hormones are used in birth.
• In response to the push of the fetus on the cervix, the maternal posterior pituitary releases oxytocin into the blood, which stimulates uterine smooth muscle contraction.
• The uterus makes prostaglandins that increase the strength of the contractions.

• A positive feedback loop is formed when the uterus senses the more powerful contractions and signals the mother's pituitary to produce more oxytocin.

• There are at least two major effects on the uterus.

• The smooth muscle cells in the cervix allow coordinated uterine contractions.

• Estradiol increases uterine sensitivity to the hormone oxytocin.

• In Chapter 50 there is a reference to the stimulation of the contraction of the uterus.
• The uterus is more sensitive to oxytocin when estradiol is high in the mother's blood near the end of pregnancy.

• The cervix is umbilical.
• The stretch is detected by the cells in the struc delivered.

• The release of oxytocin into the blood is triggered by signals from the stretch-sensitive neurons.

• There is a positive feedback loop until the baby is born.

• Female mammals eat the placenta after it passes out of the uterus.
• The uterus gets stronger in stage two.