Bio 30 Assignment #2 - Marian Canas

Development for each trimester

1st Trimester - The period during pregnancy from conception until the end of the third month. -All major systems and organs begin to form.. -The neural tube (which becomes the brain and spinal cord), the digestive system, and the heart and circulatory system begin to form. -The beginnings of the eyes and ears are developing. 2nd Trimester - The period during pregnancy from the fourth month to the end of the sixth month. -The baby's organs become fully developed during the second trimester. -The baby can also start to hear and swallow. Small hairs become noticeable. - The baby will begin to move around. 3rd Trimester - The period during pregnancy from the seventh month until birth. -Baby will open his or her eye. -Gain more weight. -Prepare for delivery. -The end of your pregnancy is near.

Progesterone

A hormone produced by the ovaries which acts with estrogen to bring about the menstrual cycle. Progesterone, hormone secreted by the female reproductive system that functions mainly to regulate the condition of the inner lining (endometrium) of the uterus. Progesterone is produced by the ovaries, placenta, and adrenal glands.

Oxytocin

A hormone released by the pituitary gland that causes increased contraction of the uterus during labour and stimulates the ejection of milk into the ducts of the breasts.

Relaxin

A hormone secreted by the placenta that causes the cervix to dilate and prepares the uterus for the action of oxytocin during labor.

Approximate dates

Cleavage - After fertilization successfully activates the egg, the egg begins a series of rapid cell divisions called cleavage. Cleavage cell divisions can occur as frequently as every 10 minutes. Gastrulation - By the end of the second week after fertilization, gastrulation occurs. In this process, the two-layered embryonic disc develops a third cell layer and a primitive gut. Implantation - Implantation of a fertilized ovum occurs between 6 to 12 days after ovulation. The blastocyst sheds its outside layer, the zona pellucida, and is replaced by a layer of underlying cells called the trophoblast.

Menstrual cycle

Cycle during which an egg develops and is released from an ovary and the uterus is prepared to receive a fertilized egg.

Chorionic villi

A product of conception. Branches of the umbilical arteries carry embryonic blood to the villi.

Umbilical cord

A tube containing the blood vessels connecting the fetus and placenta

Stages of Development

Cleavage - Cell division of zygote, in which the number of cells increases without any change in the size of the zygote. Gastrulation(layers!) -Process by which a gastrula is formed. These three germ layers are known as the ectoderm, mesoderm, and endoderm. Implantation - The process by which the zygote attaches to the uterine wall.

Formation of semen

During the process of ejaculation, sperm passes through the ejaculatory ducts and mixes with fluids from the seminal vesicles, the prostate, and the bulbourethral glands to form the semen.

Key structures originating from the 3 germ layers

Endoderm -The endoderm consists at first of flattened cells, which subsequently become columnar. It forms the epithelial lining of multiple systems. Mesoderm - Middle layer of tissue formed in the gastrula stage of the developing embryo. It is formed through a process called gastrulation. Ectoderm - The ectoderm cells differentiate into cells that form a number of external structures such as skin, sweat glands, skin sensor receptors, and hair follicles.

Estrogen

Estrogen is produced mainly in the ovaries. Estrogen is also produced by fat cells and the adrenal gland. Estrogens are hormones that are important for sexual and reproductive development, mainly in women

Allantois

Extraembryonic structure that contributes to the blood vessels of the placenta. term-19Innermost membranous sac surrounding the developing fetus.

Fertilization, Pregnancy, Development and Birth

Fertilization - the action or process of fertilizing an egg, female animal, or plant, involving the fusion of male and female gametes to form a zygote. Pregnancy - Condition in a female of having a developing embryo and fetus in her uterus for about 40 weeks Development - Starts with fertilization, in the germinal stage of embryonic development, and continues in fetal development until birth. Birth - The emergence of a baby or other young from the body of its mother; the start of life as a physically separate being.

FSH (Follicle-stimulating hormone)

Follicle-stimulating hormone.In women, this hormone stimulates the growth of ovarian follicles in the ovary before the release of an egg from one follicle at ovulation. In men, follicle stimulating hormone acts on the Sertoli cells of the testes to stimulate sperm production (spermatogenesis).

GnRH

GnRH is a hormone produced in the hypothalamus region of the brain.In response to GnRH, the pituitary releases LH, which is transported to the ovaries. Estradiol, secreted by the ovaries, then feeds back on GnRH.

Inhibin

Inhibin is produced in the gonads, pituitary gland, placenta, corpus luteum and other organs.

Amnion

Innermost membranous sac surrounding the developing fetus. A fluid-filled extraembryonic structure.

Human Chorionic Gonadotropic hormone

Is a hormone produced by the cells that surround the growing human embryo; these cells will eventually go on to form the placenta.

LH (Luteinizing hormone)

Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. In males, promotes the production of sperm cells in the seminiferous tubules. In females, stimulates ovulation and the formation and maintenance of the corpus luteum.

Chorion

Outermost layer of the two membranes surrounding the embryo; it forms the fetal part of the placenta.

Structure of the Female Reproductive System

Ovaries - (singular ovary) the female gonads, or reproductive organs; sex hormones and egg cells are produced in the ovaries. Fallopian tube - One of two tubes that connect the ovaries to the uterus. Uterus - The hollow, pear-shaped organ located between the bladder and the anus in females. Cervix - A muscular band that separates the vagina from the uterus. Vagina - The muscular canal extending from the cervix to the outer environment; the birth canal. .

Prostaglandins

Prostaglandins are found in most tissues and organs. They are produced by almost all nucleated cells. High levels of prostaglandins are produced in response to injury or infection and cause inflammation, which is associated with the symptoms of redness, swelling, pain and fever.

Structure of the male reproductive system

Testes - The male gonads, or primary reproductive organs; male sex hormones and sperm are produced in the testes. Seminiferous tubules - Produce immature sperm cells. Epididymis - Structure located along the posterior border of the testis, consisting of coiled tubules that store sperm cells. Vas deferens - Tube that conducts sperm toward the urethra. Seminal vesicles - Structure that contributes to the seminal fluid (semen), a secretion that contains fructose and prostaglandins. Ejaculatory duct - Duct formed by the union of the vas deferens with the duct of the seminal vesicle; its fluid is carried into the urethra. Prostate gland - Structure that contributes to the seminal fluid(semen), as secretion containing buffers that protect sperm cells or act as acidic environment of the vagina. Cowper's gland - Structure that contributes a mucus-rich fluid to the seminal fluid (semen). Urethra - Carries semen during ejaculation. Penis - A tube-shaped organ that extends from the trunk of the body just above the testes.

Testosterone

Testosterone is produced by the gonads (by the Leydig cells in testes in men and by the ovaries in women). In general, testosterone and other androgens promote protein synthesis and growth of those tissues with androgen receptors.

Endoderm

The inner germ layer that develops into the lining of the digestive and respiratory systems

Mesoderm

The middle layer of an embryo in early development, between the endoderm and ectoderm.

Ectoderm

The outer layer of cells in an embryo, that is the source of various tissues and structures (such as the epidermis, the nervous system, and the eyes and ears).

Placenta

The site for the exchange of nutrients and wastes between mother and fetus.

Yolk sac

a specialized structure that leads to the digestive tract of a developing organism and provides it with food during early development

Prolactin

stimulates milk production in mammary glands. Prolactin is secreted from the pituitary gland in response to eating, mating, estrogen treatment, ovulation and nursing. Prolactin plays an essential role in metabolism, regulation of the immune system and pancreatic development.