Human Development

a women may be intertile or sterile

- Blocked oviducts, often an effect of STIs - failure to ovulate, caused by hormonal imbalances that occur for a variety of reasons - endometriosis, a painful condition in which endometrial tissues grow outside the uterus - damaged eggs caused by ecposure to toxic chemicals or radiation.

A man may be infertile or sterile

- obstruction in the ductus deferens or epididymis, caused by STIS or from other blockages in the testes - low sperm count, caused by numerous factors including overheated testes, smoking, alcohol intake - inability to achieve an erection or ejaculation caused by vascular disease, nervous system injury, stress, hormonal imbalance, medication, smoking, and alcohol instake

Internal organs of the embryo form between

3 and 8 weeks. at the same time an intricate system of membranes that are external to the embryo are also forming.

Inner cell mass

Also called the embryoblast. develops into the embryo itself.

Amniotic cavity forms within a sac called

Amnion. one of several embryo-supporting strcutures.

At the end of the 8th week

As the yolk sac shrinks and the amniotic sac enlarges, the umbilical cord forms.

Placenta and umbilical cord

By the end of the second week after fertilization, finger-like projections from the chorion extend into the uterine lining.

Second trimester Week 13 to 24

By the fourth month the heartbeat of the fetus is strong enough to hear with a stethoscope. the bones of the skeleton begin to form. the brain grows rapidly and the nervous system starts to function. as the fetal legs grow and develop, the mother begins to feel movement. during the fifth month the fetus becomes covered with fine, soft hair and an oily substance to protect the still-developing skin. The hair, called lanugo is usually shed before birth. the sixth month the skin appears wrinkled because there is very little fat beneath it. the skin becomes moe pink as blood filled capillaries extend into it. if the fetus is born at this stage it is unlikely to survive.

Surrogate mother

Carries a baby or another women.

Spermicides

Chemical barriers that kill sperm. include jellies, foams, and creams. 75 percent effectiveness

Tubal ligation

Cutting the oviducts and tying off the cut ends. this ensures that the ovum never encounters sperm and never reaches the uterus. the ovum disintegrates in the oviduct

Poor nutrition can cause

Damages the placenta and can lead to low birth weight, short stature, delayed sexual development, and learning disabilities.

Gastrula

Developing embyro

Placenta

Disk-shaped organ that is rich in blood vessels. the embryo is sttached to the uterine wall by the placenta, and metabolic exchange occurs through it. the placenta is fully feveloped by about 10 weeks, with a mass of 600g

Vasectomy

Ductus deferens is cut and tied. the man is still able to have an erection and ejaculate but his semen does not contain any sperm

Blastocyst

Entire spherical structure. meaning (germ pouch) germ refers to cells from which new cells or tissues can develop. pouch is a hollow structure from which new cellular structures can develop.

Chorionic Villi

Establish the beginnings of the placenta

Fetal alcohol spectrum disorder

Fetal alcohol syndrome.

Third trimester week 25 to 38

Fetal brain cells form rapidly connecting to form more and more intricate networks. the testes of males descend into the scrotum. a layer of fat develops beneath the skin. the digestive and respirtatory systems are usually the last to mature, which is why infants that are born prematurely often have difficulty disgesting milk and breathing.

Morphogenesis

Gastrulation marks the start of this. it is the serious of events that form distinct structures of the developing organism. meaning ( shape creator/ producer of forms) depends on the abbility of early embryonic cells to become different types of cells. ( too differentiate)

Placenta

Is a structure that provides nutrients and oxygen to, and removes wastes from the developing offspring.

The passage of egg is slow

It takes about four days to reach the uterus. within 12 to 24 h of its release, or it will lose it capacity to develop further.

First trimester week 1-12

Last month of the first trimester growth in the length of the body accelerates, but growth of the head slows. cartilage based skeleton begins to harden, with the development of bone. by the end of the 12th week the external reproductive organs are distinguishable as male or female.

Sterile

Men and women who are unable to have any children.

Alcohol

Most damaging. can affect the fetus's brain, central nervous system, and physical development.

Between the 3rd and 8th week the..

Organ forms. with each passing day different rates of cell division in the primary germ layers cause tissues to fold into distinct patterns. three-layerd embryo is transformed into a body with separate organs and by about the 8th week a shape that is recognizably human.

Casearen section

Physician makes an incision in the mother's abdomen and uterus, and delivers the baby through the incision.

Superovulation

Production of multiple eggs as a result of hormone treatment. women who ovulate rarely or not at all may recieve treatment with hormones that stimulate follicle development and ovulation

Corpus Luteum

Remains intact with pregnancy but its function as a source of hormones is less important after the first trimester. by this time the placenta secretes sufficient estrogen and progesterone to maintain the endometrium

Abstinence

Staying away from a sexual relationship. you cant get pregnant and you cant get STIs

when a baby suckles..

Stimulates nerve endings in the nipple and areola. the nerve impulses travel to the hypothalamus, which in turn stimulates the posterior pituitary to release oxytocin.

Corono radiata

Surrounded by several jelly-like layers of follicle cells that loosely adhere to one another.

Embryonic Period of development

Takes place over the first eight weeks, or the first two thirds of the first trimester. cells begin to divide and become redistributed. tissues and organs form, as do structures that support and nourish the developing embyro.

Reproductive Technologies

Technologies that enhance or reduce reporductive potential- have been developed.

In vitro fertilization IVF

Technology that was designed to enhance the reproductive potential of couples who wish to have children but are unable to conceive.

Medicines that have Teratogen

Tetracycline, acne medications, anti-thyroid drugs, and some anti-cancer drugs. most important one is thalidomide

One part of the placenta..

The chorion tissue comes from the embryo. the other part consists of blood pools from the mother's circulatory system. the blood systems of the mother and embryo are separate, but they lie very close to eachother. this permits nutrients and oxygen to diffuse from the mother's circulatory system to leave the baby's circulation and enter the mother's for excretion/

During the fifth week

The embryo's head is very large compaed with its body. the eyes open, but they do not yet have eyelids or irises. cells in the brain are differentiating very quickly.

Primary germ layers

The three layers

Human chorionic gonadotropin (HCG)

The time that implantation begins, the trophoblast starts to secrete this hormone. prevents degeneration of the corpus luteum

Gastrulation

Three layers- ectoderm, inner endoderm, mesoderm

Biologists commonly divide prenatal development into three month periods called

Trimesters

Chorion

Trophoblast will develop into a membrane. this will develop to form part of the placenta

Positive feedback mechanism

Uterine contractions are induced by a stretching of the cervix, which also brings about the release of oxytocin from the posterier gland. oxytocin stimulates the uterine muscles, both directly and through the action of prostaglandins. uterine contractions push the fetus downward, and the cervix stretches even more.

Side affects of morning after pills

Vommiting and painful cramps

Teratogen

agent that causes a structural abnormality due to exposure during pregnancy. smoking can lead to no oxygen and underweight babies. it also increases the risk of premature births, stillbirths, and miscarriages.

colostrum and milk produce

antibodies

Breathing will not be required until..

baby emerges from the uterus

colostrum

before milk production, the breasts secrete colostrum which is a thin yellowish fluid protein and less fat.

Parturition

birthing process

During the second week..

blastocyst continues and completes the process of implantation, the inner cell mass changes. a space begins to form between the inner cell mass and the trophoblast.

In the sixth week

brain continues its rapid development. the limbs lengthen and flex slightly. the gonads are starting to produce hormones that will influence the development of the external genitalia.

Oxytocin

causes contractions within the mammary lobules. the mammary lobules contain alveoli, which are sacs with cells that produce milk. the lobules end in mammary ducts at the nipple

Differentiation

cellular process that enables a cell to develop a particular shape and to peform specific functions that are different from the functions of other cells. primary germ layers is important because the cells, tissues, and organs of the body are derived from the primary germ layers through differentiation.

breech birth

cervix to expand enough to accomodate this type of birth

Gamete intrafallopian transfer

eggs and sperm are brought together in the oviduct rather than in vitro. this has a higher success rate then IVF

By the end of the eighth week

embryo is about the size and mass of a paper clip. 90 percent of the organs and other structures that make up adult human body are established. as the organs enlarge and mature, until birth, the developing life is called a fetus.

The trophoblast cells secrete

enzymes that digest some of the tissues and blood vessels of the endometrium and the blastocyst slowly sinks into the uterine wall.

Afterbirth

expelled membranes and structures

The placenta does not..!

filter out substances such as alcohol, drugs, and nicotine, which can diffuse across membranes. if these substances are present in the mother's blood they will defuse into the developing baby's blood. exposure to these substances while pregnant can have severe side effects on the embryo and fetus.

Neurulation

forming a tube and marks the start of organ formation. soon after neurlation begins, a reddish bulge that contains the heart forms. by the 28th day the hear starts beating.

Morning after pills

includes several pills taken within three days after intercourse. the pills deliver high doses of synthetic estrogen and progesterone.

Fertilization

involves the joining of male and female gametes to form a single cell that contains 23 chromosomes from each parent, for a total of 46 chromosomes. in a female body, an egg is released from an ovary and swept into an oviduct. egg is carried toward the uterus by muscular contractions and the wavelike actions of cilia, which line the walls of the oviduct.

Mother's prefer to give birth in water because

it lessens the shock of the baby's entry into an atmospheric enviroment.

Physical barriers

male or female condoms. 85 percent effectiveness. latex cap called the diaphram. effectiveness 90 percent and contraceptive sponge effectiveness 70-90 percent

Infertile

men and women who have difficulty conceiving children

Contrations within the lobules cause

milk to flow to the ducts, where the infant can draw it out by suckling. if suckling does not occur, or if it stops, milk production stops within a few days.

Implantation

nestling of the blastocyst into the endometrium. it is complete by the tenth to fourteenth day. with successful implantation the women is pregnant.

Fetal period of development

nineth week through to birth. it corresponds to the remaining third of the first trimester and all of the second and third trimesters. during the fetal period, the body grows rapidly and organs begin to function and coordinate to form organ systems

Trophoblast

nourishment of the germ, forms the outer layer of the blastocyst.

zona Pellucida

plasma membrane of the egg is surrounded by a thin, clear layer of protein and carbohydrates

Cleavage

process of cell division without enlargement of the cells

Extra-embryonic membranes, along with the placenta and umbilical cord that develop are responsible for

protection, nutrition, respiration, and excretion of the embryo. during birth these membranes are expelled from the uterus.

Fourth week of prenatal development and on is a time of..

rapid growth and differntiation. blood cells start to form and fill developing blood vessels. lungs and kidneys take shape. small buds, wjich develop into arms and legs, appear. a distinct head is visible, as well as early evidence of eyes, ears, and nose.

Thalidomide

reduces morning sickness

Umbilical cord

rope-like stucture that averages about 60cm long and 2 cm in diameter. it leads from the navel area of the fetus to the centre of the placenta. it contains 2 arteries which transport oxygen-depleted blood from the fetus to the placenta. it contains one vein which brings ocygen rich blood to the fetus.

Result of HCG

secretion of estrogen and progesterone continues, maintaining the endometrium and preventing menstruation. the secretion of Hcg continues at a high level for about 2 months. then it declines to a low level by the end of four months.

Zygote

single cell/firstcell of new life. means ( joined ) 23 pairs of chromosomes. one chromosome from each pair in each parents for a total of 46 chromosomes.

Corono radiata and zona pellucida do what

source of nourishment for the egg when it was in an ovarian follicle.

Amniotic cavity

space where it will soon fill with fluid and is the place where the baby will develop.

Artificial insemination

sperm is collected and concentrated before being placed in the woman's vagina.

Fetal period of development

starts during the 9th week and lasts until birth. the fetu looks obviously human. main difference between the embryonic and the fetal periods relates to the organs. this is the time of growth and refinement

Embryonic disk

supported by a short stalk that connects the blastocyst with the endometrium. at first the embryonic disk consists of two layers: an outer ectoderm, which is closer to the amniotic cavity, and an inner endoderm. shortly after a third layer called the mesoderm forms between the endoderm and the actoderm.

Notochord will form

the basic framework of the skeleton. nervous system develops from ectoderm that is locaed just above the notochord. first cells along the notochord begin to thicken. folds develop on each side of a groove along this surface. when the folds fuse, they become a tube, called the neural tube, which develops into the brain and spinal cord.

Between the fifth and seventh day after fertilization..

the blastocyst attaches to the endometrium (outer lining of the uterus) with the inner cell mass positioned against the endometrium.

once a sperm enter's the egg

the egg's plasma membrane depolarizes, preventing other sperm from binding with and entering it. within 12 h of the sperm's nucleus entering the egg, the membranes of the sperm nucleus and the egg nucleus disappear.

during the seventh and eighth week

the embryo has distinct human characteristics. the organs are formed, and the nervous system is starting to coordinate body acitibty. a skeleton of cartilage has formed. eyes are well developed but the lids are now closed, stuck together to protect them against random movements of fingers from the still-elongating arms. the nostrils are developed, but are plugged with mucus. external genitalia are still forming, but they are undifferentiated. physical sex of the embryo is not yet apparent even though its genetic sex has been determined

prolactin

the hormone that is needed for milk production, is not secreted during pregnancy. high levels of estrogen and progesterone suppress its production in the anterior pituitary. once the mother has given birth the anterior pituitary begins to produce and secrete prolactin.

as the amniotic cavity forms

the inner cell mass flattens into a disk-shaped structure called embryonic disk.

Lactation

the secretion and formation of breast milk in the mother.

During the third week..

thickend band of mesoderm cells develops along the back of the embryonic disk. these cells lie along what will become the baby's back and come toether to form a rod-like structure called the notochord. meaning (back)

Morula

time where the zygote is a sphere of 16 cells. reaches the uterus within three to five days after fertilization. it begins to fill with fluid that diffuses from the uterus. as the fluid-filled space develops, two different groups of cells form.