what are the two germ layers?
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During gastrulation, a hollow cluster of cells called a blastula reorganizes into two primary germ layers: an inner layer, called endoderm, and an outer layer, called ectoderm.
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['Mucosa. The innermost layer of the stomach is known as the mucosa, and is made of mucous membrane. ... ', 'Submucosa. ... ', 'Muscularis. ... ', 'Serosa.']
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['Cell Membrane. A thin semipermeable membrane layer of protein and fats surrounding the cell. ... ', 'Nuclear Membrane. It is a double-membrane structure that surrounds the nucleus. ... ', 'Nucleus. ... ', 'Centrosome. ... ', 'Lysosome (Cell Vesicles) ... ', 'Cytoplasm. ... ', 'Golgi Apparatus. ... ', 'Mitochondrion.']
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['Epidermis (Epidermal Layer) Outermost layer of skin; also called cuticle or skin scarf. ... ', 'Dermis (Dermal Layer) Underlying, or inner layer of skin; also called the derma, corium, cutis or true skin. ... ', 'Subcutaneous (Subcutis or subdermis)']
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All cell walls contain two layers, the middle lamella and the primary cell wall, and many cells produce an additional layer, called the secondary wall. The middle lamella serves as a cementing layer between the primary walls of adjacent cells.
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The GI tract is composed of four layers. Each layer has different tissues and functions. From the inside out they are called: mucosa, submucosa, muscularis, and serosa. The mucosa is the innermost layer, and functions in absorption and secretion.
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Oogenesis. Oogenesis occurs in the outermost layers of the ovaries. As with sperm production, oogenesis starts with a germ cell, called an oogonium (plural: oogonia), but this cell undergoes mitosis to increase in number, eventually resulting in up to one to two million cells in the embryo.
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A single sperm and the mother's egg cell meet in the fallopian tube. When the single sperm enters the egg, conception occurs. The combined sperm and egg is called a zygote. The zygote contains all of the genetic information (DNA) needed to become a baby.
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['Epidermis. The epidermis is the most superficial layer of the skin that covers almost the entire body surface. ... ', 'Dermis. The dermis is the deep layer of the skin found under the epidermis. ... ', 'Hypodermis. ... ', 'Hair. ... ', 'Nails. ... ', 'Sudoriferous Glands. ... ', 'Sebaceous Glands. ... ', 'Ceruminous Glands.']
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['Vagina: This muscular tube receives the penis during intercourse and through it a baby leaves the uterus during childbirth.', 'Uterus: This organ holds and nourishes a developing fetus, if an egg was properly fertilized.', 'Ovaries: The female gonads, the ovaries produce ova.']
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The two main types of epithelia lining the nasopharynx are stratified squamous (comprising approximately 60% of nasopharyngeal epithelium) and pseudostratified columnar respiratory epithelium containing ciliated cells, goblet cells and basal cells.
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With the exception of the phylum Porifera (sponges), all animals have tissues that derive from embryonic germ layers. Those with two embryonic germ layers are diploblastic; those with three embryonic germ layers are triploblastic.
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['Stratum Basale. The stratum basale (also called the stratum germinativum) is the deepest epidermal layer and attaches the epidermis to the basal lamina, below which lie the layers of the dermis. ... ', 'Stratum Spinosum. ... ', 'Stratum Granulosum. ... ', 'Stratum Lucidum. ... ', 'Stratum Corneum. ... ', 'Papillary Layer. ... ', 'Reticular Layer.']
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['Stratum Basale or Basal Layer. The deepest layer of the epidermis is called the stratum basale, sometimes called the stratum germinativum. ... ', 'Stratum Spinosum or the Spiny layer. This layer gives the epidermis its strength. ... ', 'Stratum Granulosum or the Granular Layer. ... ', 'Stratum Lucidum. ... ', 'Stratum Corneum.']
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['Mucosa.', 'Submucosa.', 'Muscular layer.', 'Serous layer or serosa.']
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Among animals, sponges show the simplest organization, having a single germ layer. Although they have differentiated cells (e.g. collar cells), they lack true tissue coordination. Diploblastic animals, Cnidaria and Ctenophora, show an increase in complexity, having two germ layers, the endoderm and ectoderm.
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The skin is composed of two main layers: the epidermis, made of closely packed epithelial cells, and the dermis, made of dense, irregular connective tissue that houses blood vessels, hair follicles, sweat glands, and other structures.