`=>` `color{blue}"Chorionic villi"`: Theses are the `color{Violet}"numerous branching projections"` from the external surface of the chorion that provide for exchange between the `color{Violet}"maternal and fetal circulation"`. `color{Violet}"Oxygen and nutrients"` in the maternal blood diffuse through the walls of the villi and enter the blood of the embryo or fetus. `color{Violet}"Carbon dioxide and waste"` products diffuse from blood in the fetal capillaries through the walls of the villi into the maternal blood.
`=>` `color{blue}"Placenta"` : The placenta is an organ that connects the `color{Violet}"developing fetus to the uterine wall"` to allow nutrient uptake, thermo-regulation, waste elimination, and gas exchange via the mother's blood supply; to fight against internal infection; and to produce hormones which support pregnancy. The placenta provides `color{Violet}"oxygen and nutrients"` to growing fetuses and removes `color{Violet}"waste products"` from the fetus's blood. It comes from Greek plakóenta/plakoúnta, meaning `color{Violet}"flat, slab-like"`, in reference to its round, flat appearance in humans.
`=>` `color{blue}"Embryonic Layers"`: An `color{Violet}"Embryonic layer (germ layer)"` is a primary layer of cells that form during embryogenesis from which the `color{Violet}"endoderm, mesoderm, and ectoderm"` arise. From these layers of cells arise all of the `color{Violet}"structures and organs"` and parts of the body. The `color{Violet}"endoderm and ectoderm"` are the first to develop.
`=>` `color{blue}"Ectoderm"`: `color{Violet}"Ectoderm"` is the the outermost of the three germ layers, or masses of cells, which appears early in the development of an `color{Violet}"animal embryo"`. In vertebrates, ectoderm subsequently gives rise to `color{Violet}"hair, skin, nails or hooves"`, and the lens of the eye; the `color{Violet}"epithelia"` (surface, or lining, tissues) `color{Violet}"of sense organs"`, the nasal cavity, the sinuses, the `color{Violet}"mouth (including tooth enamel)"`, and the anal canal; and nervous tissue.
`=>` `color{blue}"Endoderm"`: `color{Violet}"Endoderm"`, the innermost of the three germ layers, or masses of cells (lying within ectoderm and mesoderm), which appears early in the development of an `color{Violet}"animal embryo"`. The endoderm subsequently gives rise to the epithelium (tissue that covers, or lines, a structure) of the `color{Violet}"pharynx"`, including the eustachian tube, the tonsils, the thyroid gland, parathyroid glands, and thymus gland; the `color{Violet}"larynx, trachea, and lungs"`; the `color{Violet}"gastrointestinal tract"` (except mouth and anus), the `color{Violet}"urinary bladder, the vagina"` (in females), and the urethra.
`=>` `color{blue}"Mesoderm"`: `color{Violet}"Mesoderm"`, the middle of the three germ layers, or masses of cells (lying between the ectoderm and endoderm), which appears early in the development of an `color{Violet}"animal embryo"`. In vertebrates it subsequently gives rise to `color{Violet}"muscle, connective tissue,"` `color{Violet}"cartilage, bone, notochord, blood,"` bone marrow, lymphoid tissue, and to the epithelia (surface, or lining, tissues) of blood vessels, lymphatic vessels, body cavities, kidneys, ureters, gonads (sex organs), genital ducts, adrenal cortex, and certain other tissues.
`color{green} ✍️ color{green} mathbf("KEY CONCEPT")`
● After implantation, `color{Violet}"finger-like projections"` appear on the trophoblast called `color{Violet}"chorionic villi"` which are surrounded by the uterine tissue and maternal blood.
● The `color{Violet}"chorionic villi"` and `color{Violet}"uterine tissue"` become `color{Violet}"interdigitated"` with each other and jointly form a `color{Violet}"structural and"` `color{Violet}"functional unit"` between developing embryo (fetus) and maternal body called `color{Violet}"placenta"` .
● The `color{Violet}"placenta"` facilitates the `color{Violet}"supply"` of oxygen and nutrients to the embryo and also `color{Violet}"removal"` of carbon dioxide and excretory/waste materials produced by the embryo.
● The placenta is connected to the embryo through an `color{Violet}"umbilical cord"` which helps in the `color{Violet}"transport"` of substances to and from the embryo.
● Placenta also acts as an endocrine tissue and produces several hormones like `color{Violet}"human chorionic gonadotropin (hCG)"`, `color{Violet}"human placental lactogen (hPL)"`, `color{Violet}"estrogens"`, `color{Violet}"progestogens"`, etc.
● In the `color{Violet}"later phase"` of pregnancy, a hormone called `color{Violet}"relaxin"` is also secreted by the ovary.
● Thus, `color{Violet}"hCG, hPL"` `color{Violet}"and relaxin"` are produced in women only during `color{Violet}"pregnancy"`.
● In addition, during pregnancy the `color{Violet}"levels"` `color{Violet}"of other hormones"` like estrogens, progestogens, cortisol, prolactin, thyroxine, etc., are `color{Violet}"increased"` several folds in the maternal blood.
● `color{Violet}"Increased production"` of these hormones is essential for supporting the `color{Violet}"fetal growth"`, `color{Violet}"metabolic changes"` in the mother and `color{Violet}"maintenance"` of pregnancy.
● Immediately after implantation, the `color{Violet}"inner cell mass"` (embryo) differentiates into an outer layer called `color{Violet}"ectoderm"` and an inner layer called `color{Violet}"endoderm"`.
● A `color{Violet}"mesoderm"` soon appears between the ectoderm and the endoderm.
● These `color{Violet}"three layers"` give rise to all tissues (organs) in adults.
● The `color{Violet}"inner cell mass"` contains certain cells called `color{Violet}"stem cells"` which have the potency to give rise to all the `color{Violet}"tissues and organs"`.
`=>` `color{blue}"Chorionic villi"`: Theses are the `color{Violet}"numerous branching projections"` from the external surface of the chorion that provide for exchange between the `color{Violet}"maternal and fetal circulation"`. `color{Violet}"Oxygen and nutrients"` in the maternal blood diffuse through the walls of the villi and enter the blood of the embryo or fetus. `color{Violet}"Carbon dioxide and waste"` products diffuse from blood in the fetal capillaries through the walls of the villi into the maternal blood.
`=>` `color{blue}"Placenta"` : The placenta is an organ that connects the `color{Violet}"developing fetus to the uterine wall"` to allow nutrient uptake, thermo-regulation, waste elimination, and gas exchange via the mother's blood supply; to fight against internal infection; and to produce hormones which support pregnancy. The placenta provides `color{Violet}"oxygen and nutrients"` to growing fetuses and removes `color{Violet}"waste products"` from the fetus's blood. It comes from Greek plakóenta/plakoúnta, meaning `color{Violet}"flat, slab-like"`, in reference to its round, flat appearance in humans.
`=>` `color{blue}"Embryonic Layers"`: An `color{Violet}"Embryonic layer (germ layer)"` is a primary layer of cells that form during embryogenesis from which the `color{Violet}"endoderm, mesoderm, and ectoderm"` arise. From these layers of cells arise all of the `color{Violet}"structures and organs"` and parts of the body. The `color{Violet}"endoderm and ectoderm"` are the first to develop.
`=>` `color{blue}"Ectoderm"`: `color{Violet}"Ectoderm"` is the the outermost of the three germ layers, or masses of cells, which appears early in the development of an `color{Violet}"animal embryo"`. In vertebrates, ectoderm subsequently gives rise to `color{Violet}"hair, skin, nails or hooves"`, and the lens of the eye; the `color{Violet}"epithelia"` (surface, or lining, tissues) `color{Violet}"of sense organs"`, the nasal cavity, the sinuses, the `color{Violet}"mouth (including tooth enamel)"`, and the anal canal; and nervous tissue.
`=>` `color{blue}"Endoderm"`: `color{Violet}"Endoderm"`, the innermost of the three germ layers, or masses of cells (lying within ectoderm and mesoderm), which appears early in the development of an `color{Violet}"animal embryo"`. The endoderm subsequently gives rise to the epithelium (tissue that covers, or lines, a structure) of the `color{Violet}"pharynx"`, including the eustachian tube, the tonsils, the thyroid gland, parathyroid glands, and thymus gland; the `color{Violet}"larynx, trachea, and lungs"`; the `color{Violet}"gastrointestinal tract"` (except mouth and anus), the `color{Violet}"urinary bladder, the vagina"` (in females), and the urethra.
`=>` `color{blue}"Mesoderm"`: `color{Violet}"Mesoderm"`, the middle of the three germ layers, or masses of cells (lying between the ectoderm and endoderm), which appears early in the development of an `color{Violet}"animal embryo"`. In vertebrates it subsequently gives rise to `color{Violet}"muscle, connective tissue,"` `color{Violet}"cartilage, bone, notochord, blood,"` bone marrow, lymphoid tissue, and to the epithelia (surface, or lining, tissues) of blood vessels, lymphatic vessels, body cavities, kidneys, ureters, gonads (sex organs), genital ducts, adrenal cortex, and certain other tissues.
`color{green} ✍️ color{green} mathbf("KEY CONCEPT")`
● After implantation, `color{Violet}"finger-like projections"` appear on the trophoblast called `color{Violet}"chorionic villi"` which are surrounded by the uterine tissue and maternal blood.
● The `color{Violet}"chorionic villi"` and `color{Violet}"uterine tissue"` become `color{Violet}"interdigitated"` with each other and jointly form a `color{Violet}"structural and"` `color{Violet}"functional unit"` between developing embryo (fetus) and maternal body called `color{Violet}"placenta"` .
● The `color{Violet}"placenta"` facilitates the `color{Violet}"supply"` of oxygen and nutrients to the embryo and also `color{Violet}"removal"` of carbon dioxide and excretory/waste materials produced by the embryo.
● The placenta is connected to the embryo through an `color{Violet}"umbilical cord"` which helps in the `color{Violet}"transport"` of substances to and from the embryo.
● Placenta also acts as an endocrine tissue and produces several hormones like `color{Violet}"human chorionic gonadotropin (hCG)"`, `color{Violet}"human placental lactogen (hPL)"`, `color{Violet}"estrogens"`, `color{Violet}"progestogens"`, etc.
● In the `color{Violet}"later phase"` of pregnancy, a hormone called `color{Violet}"relaxin"` is also secreted by the ovary.
● Thus, `color{Violet}"hCG, hPL"` `color{Violet}"and relaxin"` are produced in women only during `color{Violet}"pregnancy"`.
● In addition, during pregnancy the `color{Violet}"levels"` `color{Violet}"of other hormones"` like estrogens, progestogens, cortisol, prolactin, thyroxine, etc., are `color{Violet}"increased"` several folds in the maternal blood.
● `color{Violet}"Increased production"` of these hormones is essential for supporting the `color{Violet}"fetal growth"`, `color{Violet}"metabolic changes"` in the mother and `color{Violet}"maintenance"` of pregnancy.
● Immediately after implantation, the `color{Violet}"inner cell mass"` (embryo) differentiates into an outer layer called `color{Violet}"ectoderm"` and an inner layer called `color{Violet}"endoderm"`.
● A `color{Violet}"mesoderm"` soon appears between the ectoderm and the endoderm.
● These `color{Violet}"three layers"` give rise to all tissues (organs) in adults.
● The `color{Violet}"inner cell mass"` contains certain cells called `color{Violet}"stem cells"` which have the potency to give rise to all the `color{Violet}"tissues and organs"`.