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By L. Grimboll. Methodist Theological School in Ohio.

Define tissue and explain why histology is important to the study of anatomy generic 0.5 mg decadron amex, physiology, and medicine. Explain how the matrix permits specific kinds of cells to be even more effec- tive and functional as tissues. Histology © The McGraw−Hill Anatomy, Sixth Edition of the Body Companies, 2001 Developmental Exposition Embryoblast Blastocoele Amniotic cavity (c) Trophoblast Ectoderm Endoderm (b) Amniotic cavity (d) Ectoderm Embryonic disc Mesoderm (a) Endoderm Yolk sac Trophoblast (e) Schenk EXHIBIT 1 The early stages of embryonic development. Within 30 hours after fertilization, the zygote undergoes a The Tissues mitotic division as it moves through the uterine tube toward the uterus (see chapter 22). After several more cellular divisions, the embryonic mass consists of 16 or more cells and is called a EXPLANATION morula (mor′yoo-la˘), as shown in exhibit I. Three or 4 days after Human prenatal development is initiated by the fertilization of conception, the morula enters the uterine cavity where it re- an ovulated ovum (egg) from a female by a sperm cell from a mains unattached for about 3 days. The chromosomes within the nucleus of a zygote (zı˘go¯t) of the morula fills with fluid absorbed from the uterine cavity. As (fertilized egg) contain all the genetic information necessary for the fluid-filled space develops inside the morula, two distinct the differentiation and development of all body structures. There are two major categories of epithelia: membranous and Objective 6 Define gland and compare and contrast the glandular. Membranous epithelia are located throughout the body various types of glands in the body. Glandular epithelia are specialized tissues that form the secretory portion of glands. Characteristics of Membranous Epithelia Objective 4 Compare and contrast the various types of Membranous epithelia always have one free surface exposed to a membranous epithelia. Histology © The McGraw−Hill Anatomy, Sixth Edition of the Body Companies, 2001 (continued) TABLE 4A Derivatives of the Germ Layers Ectoderm Mesoderm Endoderm Epidermis of skin and epidermal derivatives: Muscle: smooth, cardiac, skeletal Epithelium of pharynx, auditory canal, tonsils, hair, nails, glands of the skin; linings of oral, Connective tissue: embryonic, mesenchyme, thyroid, parathyroid, thymus, larynx, trachea, nasal, anal, and vaginal cavities connective tissue proper, cartilage, bone, blood lungs, GI tract, urinary bladder and urethra, and Nervous tissue; sense organs vagina Dermis of skin; dentin of teeth Lens of eye; enamel of teeth Liver and pancreas Epithelium (endothelium) of blood vessels, Pituitary gland lymphatic vessels, body cavities, joint cavities Adrenal medulla Internal reproductive organs Kidneys and ureters Adrenal cortex wall is known as the trophoblast, and the inner aggregation of is closer to the amniotic cavity, and a lower endoderm, which cells is known as the embryoblast.

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Re- while sour substances may produce depolarization by view of Medical Physiology order decadron 1 mg without prescription. Molecules to be sensed must be dissolved in this mucous This represents a 10 million-fold difference in sensitivity. The basal ends of the receptor cells form axonal The basis for odor discrimination is not well understood. It processes called fila olfactoria that pass through the cribri- is not likely that there is a receptor molecule for every pos- form plate of the ethmoid bone. These short axons synapse sible odor substance located in the membranes of the ol- with the mitral cells in complex spherical structures called factory cilia, and it appears that complex odor sensations olfactory glomeruli located in the olfactory bulb, part of arise from unique spatial patterns of activation throughout the brain located just above the olfactory mucosa. Approximately 1,000 fila olfactoria a molecule of an odorous substance to a G protein-cou- synapse on each mitral cell, resulting in a highly conver- pled receptor on a cilium of a sensory cell. Lateral connections are also plentiful in causes the production of cAMP that binds to, and opens, the olfactory bulb, which also contains efferent fibers sodium channels in the ciliary membrane. They are sensitive to cer- arise in the initial segments of the fila olfactoria. The tain odorous substances, such as peppermint and chlorine, sense of smell shows a high degree of adaptation, some of and play a role in the initiation of reflex responses (e. Discrimination between into convenient classes, though some general categories, odor intensities is not well defined; detectable differ- such as flowery, sweaty, or rotten, may be distinguished. REVIEW QUESTIONS DIRECTIONS: Each of the numbered (B) An age-related loss of cells in the held still will result in the perception items or incomplete statements in this retina of section is followed by answers or (C) Change in the elasticity of the lens (A) Being upside-down completions of the statement. Select the as a result of age (B) Moving in a straight line ONE lettered answer or completion that is (D) A loss of transparency in the lens (C) Continued rotation BEST in each case. A decrease in sensory response while a frequency in a sensory nerve usually a myopic eye compensate for distance stimulus is maintained constant is due signifies vision? Sensory receptors that adapt rapidly (E) An increase in the action potential of the eye are well suited to sensing conduction velocity (D) Eyeglasses that are partially (A) The weight of an object held in 2.

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