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Evagination
Endodermic evagination relates to the inner germ layers of cells of the very early embryo, from which is formed the lining of the digestive tract, of other internal organs, and of certain glands, implies the extension of a layer of body tissue to form a pouch, or the turning inside out (protrusion) of some body part or organ from its basic position, for example the para-nasal sinuses are believed to be formed in the fetus by 'ballooning' of the developing nasal canal, and the prostate or Skene's gland formed out of evaginations of the urethra. See also *List of human cell types derived from the germ layers This is a list of Cell (biology), cells in humans derived from the three embryonic germ layers – ectoderm, mesoderm, and endoderm. Cells derived from ectoderm Surface ectoderm Skin * Trichocyte (human), Trichocyte * Keratinocyte Anterior pi ... References Embryology Developmental biology {{developmental-biology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prostate
The prostate is an male accessory gland, accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found in all male mammals. It differs between species anatomically, chemically, and physiologically. Anatomically, the prostate is found below the bladder, with the urethra passing through it. It is described in gross anatomy as consisting of lobes and in microanatomy by zone. It is surrounded by an elastic, fibromuscular capsule and contains glandular tissue, as well as connective tissue. The prostate produces and contains fluid that forms part of semen, the substance emitted during ejaculation as part of the male human sexual response cycle, sexual response. This prostatic fluid is slightly Alkalinity, alkaline, milky or white in appearance. The alkalinity of semen helps neutralize the acidity of the vagina, vaginal tract, prolonging the lifespan of sperm. The prostatic fluid is expelled in the first part of ej ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Germ Layer
A germ layer is a primary layer of cell (biology), cells that forms during embryonic development. The three germ layers in vertebrates are particularly pronounced; however, all eumetazoans (animals that are sister taxa to the sponges) produce two or three primary germ layers. Some animals, like cnidarians, produce two germ layers (the ectoderm and endoderm) making them diploblastic. Other animals such as bilaterians produce a third layer (the mesoderm) between these two layers, making them triploblastic. Germ layers eventually give rise to all of an animal's Tissue (biology), tissues and organ (anatomy), organs through the process of organogenesis. History Caspar Friedrich Wolff observed organization of the early embryo in leaf-like layers. In 1817, Heinz Christian Pander discovered three primordial germ layers while studying chick embryos. Between 1850 and 1855, Robert Remak had further refined the germ cell layer (''Keimblatt'') concept, stating that the external, internal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skene's Gland
In female human anatomy, Skene's glands or the Skene glands ( , also known as the lesser vestibular glands or paraurethral glands) are two glands located towards the lower end of the urethra. The glands are surrounded by tissue that swells with blood during sexual arousal, and secrete a fluid, carried by the Skene's ducts to openings near the urethral meatus, particularly during orgasm. Structure and function The Skene's glands' openings are located in the vestibule of the vulva, around the lower end of the urethra. The two Skene's ducts lead from the Skene's glands to the vulvar vestibule, to the left and right of the urethral opening, from which they are structurally capable of secreting fluid. Although there remains debate about the function of the Skene's glands, one purpose is to secrete a fluid that helps lubricate the urethral opening. Skene's glands produce a milk-like ultrafiltrate of blood plasma. The glands may be the source of female ejaculation, but this has n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Urethra
The urethra (: urethras or urethrae) is the tube that connects the urinary bladder to the urinary meatus, through which Placentalia, placental mammals Urination, urinate and Ejaculation, ejaculate. The external urethral sphincter is a striated muscle that allows voluntary control over urination. The Internal urethral sphincter, internal sphincter, formed by the involuntary smooth muscles lining the bladder neck and urethra, receives its nerve supply by the Sympathetic nervous system, sympathetic division of the autonomic nervous system. The internal sphincter is present both in males and females. Structure The urethra is a fibrous and muscular tube which connects the urinary bladder to the external urethral meatus. Its length differs between the sexes, because it passes through the penis in males. Male In the human male, the urethra is on average long and opens at the end of the external urethral meatus. The urethra is divided into four parts in men, named after the lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Human Cell Types Derived From The Germ Layers
This is a list of Cell (biology), cells in humans derived from the three embryonic germ layers – ectoderm, mesoderm, and endoderm. Cells derived from ectoderm Surface ectoderm Skin * Trichocyte (human), Trichocyte * Keratinocyte Anterior pituitary * Gonadotropic cell, Gonadotrope * Corticotropic cell, Corticotrope * Thyrotropic cell, Thyrotrope * Somatotropic cell, Somatotrope * Prolactin cell, Lactotroph Tooth enamel * Ameloblast Neural crest Peripheral nervous system * Neuron * Neuroglia, Glia ** Schwann cell ** Satellite glial cell Neuroendocrine system * Chromaffin cell * Glomus cell Skin * Melanocyte ** Nevus cell * Merkel cell Teeth * Odontoblast * Cementoblast Eyes * Corneal keratocyte Smooth muscle Neural tube Central nervous system * Neuron * Glia ** Astrocyte ** Ependyma, Ependymocytes ** Müller glia (retina) ** Oligodendrocyte ** Oligodendrocyte progenitor cell ** Pituicyte (posterior pituitary) Pineal gland * Pinealocyte Cells derived from mesoderm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryology
Embryology (from Ancient Greek, Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, ''-logy, -logia'') is the branch of animal biology that studies the Prenatal development (biology), prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses. Additionally, embryology encompasses the study of congenital disorders that occur before birth, known as teratology. Early embryology was proposed by Marcello Malpighi, and known as preformationism, the theory that organisms develop from pre-existing miniature versions of themselves. Aristotle proposed the theory that is now accepted, Epigenesis (biology), epigenesis. Epigenesis (biology), Epigenesis is the idea that organisms develop from seed or egg in a sequence of steps. Modern embryology developed from the work of Karl Ernst von Baer, though accurate observations had been made in Italy by anatomists such as Aldrovandi and Leonardo da Vinci in the Renaissance. Comparative ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
