A pregnant lioness.

In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus; and ends once it leaves the uterus. A pregnant woman near the end of her term Pregnancy is the carrying of one or more embryos or fetuses by female mammals, including humans, inside their bodies. ... Image File history File links PregnantLioness. ... Image File history File links PregnantLioness. ... For other uses, see Reproduction (disambiguation) Reproduction is the biological process by which new individual organisms are produced. ... This article or section does not cite any references or sources. ... Implantation occurs when a fertilized zygote attaches itself onto the lining of the uterus. ... Gestation is the carrying of an embryo or fetus inside a female viviparous animal. ... A sperm cell fertilizing an ovum This article is about reproduction in organisms. ... It has been suggested that Biparental zygote be merged into this article or section. ...

Fertilization and implantation

A male and female copulate, the male inseminating the female. The spermatozoan fertilizes an ovum or various ova in the uterus or fallopian tubes, and this results in one or multiple zygotes. Sometimes, a zygote can be created by humans outside of the animal's body in the artificial process of in-vitro fertilization. After fertilization, the newly formed zygote then begins to divide through mitosis, forming an embryo, which implants in the female's endometrium. At this time, the embryo usually consists of 16 cells. The shield and spear of the Roman god Mars, which is also the alchemical symbol for iron, represents the male sex. ... This article or section does not cite any references or sources. ... A pair of lions copulating in the Maasai Mara, Kenya. ... Insemination is the introduction of semen into the genital tract of a female. ... Schematic diagram of a sperm cell, showing the (1) acrosome, (2) cell membrane, (3) nucleus, (4) mitochondria, and (5) flagellum (tail) A sperm cell, or spermatozoon ( spermatozoa) (in Greek: sperm = semen and zoon = alive), is the haploid cell that is the male gamete. ... A sperm cell fertilizing an ovum This article is about reproduction in organisms. ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... The uterus or womb is the major female reproductive organ of most mammals, including humans. ... Female internal reproductive anatomy The Fallopian tubes or oviducts are two very fine tubes leading from the ovaries of female mammals into the uterus. ... It has been suggested that Biparental zygote be merged into this article or section. ... In vitro fertilization (IVF) is a technique in which egg cells are fertilized outside the mothers body in cases where conception is difficult or impossible through normal intercourse. ... 68. ... It has been suggested that embryology be merged into this article or section. ... The endometrium is the inner membrane of the mammalian uterus. ...

Birth hurts...

Development

After implantation

A blastocele is a small cavity on the center of the embryo, and the developing embryonary cells will grow around it. Then, a flat layer cell forms on the exterior of this cavity, and the zona pellucida, the blastocyst's barrier, remains the same size as before. Cells grow increasingly smaller to fit in. This new structure with a cavity in the center and the developing cells around it is known as a blastocyst. A blastocoel(e) or blastocele or cleavage cavity or segmentation cavity is the central region of a blastula (or blastosphere). ... The zona pellucida (or zona striata in older texts) is a glycoprotein membrane surrounding the plasma membrane of an oocyte. ... The blastocyst is the structure formed in early mammalian embryogenesis, after the formation of the blastocele, but before implantation. ...

The presence of the blastocyst means that two types of cells are forming, an inner-cell mass growing on the interior of the blastocele and cells growing on the exterior of it. In 24 to 48 hours, the zona pellucida breaches. The cells on the exterior of the blastocyst begin excreting an enzyme which erodes epithelial uterine lining and creates a site for implantation. Types of epithelium This article discusses the epithelium as it relates to animal anatomy. ...

A pregnant woman at 26 weeks. Human Pregnancy is the most studied of all mammalian pregnancies.

Image File history File linksMetadata Download high resolution version (1203x2048, 178 KB) Summary Dag boeleke! Pregnancy in the 26th week. ... Image File history File linksMetadata Download high resolution version (1203x2048, 178 KB) Summary Dag boeleke! Pregnancy in the 26th week. ... Trinomial name Homo sapiens sapiens Linnaeus, 1758 Humans, or human beings, are bipedal primates belonging to the mammalian species Homo sapiens (Latin: wise man or knowing man) in the family Hominidae (the great apes). ... A pregnant woman near the end of her term Pregnancy is the carrying of one or more embryos or fetuses by female mammals, including humans, inside their bodies. ...

Placental circulation system

The cells surrounding the blastocyst now destroy cells in the uterine lining, forming small pools of blood, which in turn stimulate the production of capillaries. This is the first stage in the growth of the placenta. The inner cell mass of the blastocyst divides rapidly, forming two layers. The top layer becomes the embryo, and cells from there occupy the amniotic cavity. At the same time, the bottom layer forms a small sac. (If the cells begin developing in an abnormal position, an ectopic gestation may also occur at this point.) The placenta is an ephemeral (temporary) organ present in female placental vertebrates during gestation (pregnancy), but a placenta has evolved independently also in other animals as well, for instance scorpions and velvet worms. ...

Several days later, chorionic villi in the forming placenta anchor the implantation site to the uterus. A system of blood and blood vessels now develops at the point of the newly forming placenta, growing near the implantation site. The small sac inside the blastocyst begins producing red blood cells. For the next 24 hours, connective tissue develops between the developing placenta and the growing fetus. This later develops into the umbilical cord. The chorion undergoes rapid proliferation and forms numerous processes, the chorionic villi, which invade and destroy the uterine decidua and at the same time absorb from it nutritive materials for the growth of the embryo. ... f you all The blood vessels are part of the circulatory system and function to transport blood throughout the body. ... Human red blood cells Red blood cells are the most common type of blood cell and the vertebrate bodys principal means of delivering oxygen from the lungs or gills to body tissues via the blood. ... Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, muscle, and nervous tissue. ... Human fetus at eight weeks. ... In placental mammals, the umbilical cord is a tube that connects a developing embryo or fetus to its placenta. ...

Cellular differentiation

Following this, a narrow line of cells appears on the surface on the embryo. Its growth makes the fetus undergo gastrulation, in which the three primary tissue layers of the fetus, the ectoderm, mesoderm, and endoderm, develop. The narrow line of cells begin to form the endoderm and mesoderm. The ectoderm begins to grow rapidly as a result of chemicals being produced by the mesoderm. These three layers give rise to all the various types of tissue in the body. 1 - blastula, 2 - gastrula; orange - ectoderm, red - endoderm. ... Organs derived from each germ layer. ...

The endoderm later forms the lining of the tongue, digestive tract, lungs, bladder and several glands. The mesoderm forms muscle, bone and lymph tissue, as well as the interior of the lungs, heart, reproductive and excretory systems. It also gives rise to the spleen, and produces blood cells. The ectoderm forms the skin, nails, hair, cornea, lining of the internal and external ear, nose, sinuses, mouth, anus, teeth, pituitary gland, mammary glands, eyes and all parts of the nervous system. This article includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and... Human respiratory system The lungs flank the heart and great vessels in the chest cavity. ... In anatomy, the urinary bladder is a hollow, muscular, and distensible (or elastic) organ that sits on the pelvic floor in mammals. ... Human submaxillary gland. ... A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ... Grays Anatomy illustration of a human femur. ... In mammals including humans, the lymphatic vessels (or lymphatics) are a network of thin tubes that branch, like blood vessels, into tissues throughout the body. ... The heart and lungs, from an older edition of Grays Anatomy. ... The reproductive system is the ensembles and interactions of organs and/or substances within an organism that strictly pertain to reproduction. ... Kidneys Nephron Urine Large Intestine Lung Carbon dioxide Skin Sweat Bile Malphigian tubule system (Arthropod excretory system) Menses The Excretory system is responsible for the elimination of wastes produced by homeostasis. ... The spleen is an organ located the abdomen, where it functions in the destruction of old white blood cells and holding a reservoir of blood. ... In zootomy and dermatology, skin is the largest organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs. ... Anatomy In anatomy, a nail is a horn-like piece at the end of a humans or an animals finger or toe. ... A strand of human hair under magnification Hair is also the name of a musical, see respective articles for the stage production and the movie. ... The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... A pierced human ear. ... For the article about nose in humans, see human nose Human nose in profile Elephants have prehensile noses Dogs have very sensitive noses Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration in conjunction with the mouth. ... The term sinus (Latin for bay, pocket, curve or bosom) is used in various contexts. ... It has been suggested that this article or section be merged with mouth (human). ... Female Human Anatomy Male Human Anatomy This article is about the bodily orifice. ... The visible teeth of a smile. ... Located at the base of the skull, the pituitary gland is protected by a bony structure called the sella turcica. ... Mammary glands are the organs that, in the female mammal, produce milk for the sustenance of the young. ... // A human eye. ... The Human Nervous System The nervous system of a human coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. ...

Approximately 18 days after fertilization, the embryo has divided to form much of the tissue it will need. It is shaped like a pear, where the head region is larger than the tail. The embryo's nervous system is one of the first organic systems to grow. It begins growing in a concave area known as the neural groove. Between the neural folds is a shallow median groove, the neural groove. ...

The blood system continues to grow networks which allow the blood to flow around the embryo. Blood cells are already being produced and are flowing through these developing networks. Secondary blood vessels also begin to develop around the placenta, to supply it with more nutrients. Blood cells begin to form on the sac in the center of the embryo, as well as cells which begin to differentiate into blood vessels. Endocardial cells begin to form the myocardium. Cellular differentiation is a concept from developmental biology describing the process by which cells acquire a type. The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptions. ... In the heart, the endocardium is the innermost layer of tissue that lines the chambers of the heart. ... Myocardium is the muscular tissue of the heart. ...

At about 24 days past fertilization, there is a primitive S-shaped tubule heart which begins beating. The flow of fluids throughout the embryo will begin at this stage.