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Histology SCUHS

Histology

QuestionAnswer
Excitability Is ability to produce action potential in response to a stimulus.
Conductivity Ability to propagate action potential along the neural membrane.
Neurons Are cells with mult. processes, one axon conducting action potentials away from the cell body and one or more dentrites conducting graded potentials twrd. the cell body.
Neuroglia Cells Cells of supoort to the nerve cells and their processes. They're of 2 main types, ea. has various subtypes.
Cell body Contains: Mitochondria, golgi body, ER, neurofibrils, neurotubules, Nissl Bodies, and Nucleus.
Dendrites conducts graded potentials twrd. the cell body. May be more than one, usually short, thick. Cytoplasm shows all organelles existing in cell body. Surface membrane shows dendritic spines or gemmules as sites of cellular synapses.
Axon Conducts action potentiala way from the cell body. ONLY ONE per cell. usually thing and long. comes from cell body (axon hillocks). The axoplasm lacks Nissl Granules. Telodendria terminate in bulbous endings called terminal boutons.
Unipolar/Pseudounipolar with one process (spinal Ganglia)
Bipolar With 2 processes (retina)
Multipolar with more than 2 processes; Stellate - star-shaped, (autonomic ganglia) Pyramidal - (Cerebral Cortex) Piriform - pear-shaped ( Cerebullum) Granule cells - small with nucleus filling most of the cell (Cerebellum)
Golgi Type I cells has long axons
Golgi Type II cells contains short axons
3 types of synaptic contacts: Axosomatic Axodendritic Axoaxonic
Synaptic Vesicles has elements of multiple mitochondria and membraneous vesicles in the presynaptic element.
Myelin sheath mainly formed by lipid & some protein; divided by internodal segemts (nodes of Ranvier) to speed up (saltatory) conduction
Neurolemma (Schwann's Sheath) lie outside the myelin sheath; contain flat cells/flat nuclei (schwann cells)wraps around for protective covering does help with regeneration of nerves forming myelin sheath.
Nacked Fibers No coverings [Ex] grey matter of CNS
Myelinated but no neurolemma Ex] White matter of CNS
Neurolemma but no myelin Ex] autonomic nerves
neurolemma and myelin Ex] Spinal nerves
Neuroglia proper (Neuroglia cells) Exists only in CNS; Astrocytes, Oligodendroglia, & microglia.
Modified neuroglia (Neuroglia cells) Found both in CNS & PNS; Neurolemma cells, Satelitte cells (Schwann cells), Ependymal cells
Astrocytes star shaped cells with multiple processes ending by pervascular feet over blood vessels. They form Blood Brain Barrier. SUBTYPES: Protoplasmic- have thicker, more branching processes & found in gray matter of CNS; FIBROUS ASTROCYTES.
FIBROUS ASTROCYTES thinner & less branching processes, are found in white matter of CNS, develop from the ectoderm.
Oligodendroglia round with few processes, found in both gray & white matters of CNS, form myelin sheath around nerves and develop from ectoderm.
Microglia small spindle cells with processes at the poles. Are Phagocytic cells arising from mesdoderm and found in both gray and white matter of CNS
Neurolemma cells present only in PNS
Satellite Cells Surrounding cells bodies of neurons inside ganglia (PNS)
Ependymal Cells columnar cells with some cilia, lining ventricles of the brain & central canal of spinal cord.
Endoneurium loose C.T. lies outside the neurolemma,
Perineurium surrounds bundles of fibers by a C.T. membrane
Epineurium Coveres the whole nerve by a C.T. membrane
Peripheral Nervous System which includes: Peripheral Nerves, Ganglia, Nerve Endings
Central Nervous System -Brain: Cerebrum, Brain Stem (midbrain, pons, & medulla oblongata), Cerebellum. -Spinal Cord:
Ganglia Collections of nerve cells outside the CNS along the course of spinal & autonomic nerves. 2 types: spinal & autonomic ganglia.
Autonomic Ganglion Smaller; Multipolar Stellate; 15-40 microns; Larger in # relative to size of ganglion; cells are scattered irregularly; Cell nuclei: mostly eccentric; Satellite sheath: incomplete; NERVE FIBERS ARE NON-MYELINATED.
Spinal Ganglion Larger; Pseudounipolar; 25-100 microns; running parallel to capsule of ganglion; Cell nuclei: mostly central; Satellite sheath: almost complete; Nerve fibers are myelinate(most) and non-myelinated.
Exteroceptors are receptors close to body surfaces and they receive impulses that originate from outside the body
Free Nerve endings originate from sub-epithelial plexus of sensory nerves, lose their sheaths and penetrate naked in epithelial cells. Sensitive to pain stimuli, may carry light touch and temperature stimuli.
Peritrichial plexus similar to free endings, but around hair follicles.
merkel'S tactile corpuscles naked nerve terminal penetrates btw epithelial cells and expands into a tactile meniscus around a specialized epithelial cell, its sensitive to light touch.
meissner's corpuscles encapsulated nerve endings located in dermal papillae, CT capsule is oval in shape. Sensitive to light touch and are common in the skin of the fingertips and toes, lips, nipples, and genitalia.
Genital corpuscles capsule is rounded, found in glans penis, clitoris, and labia minora, light touch.
Ruffini corpuscles Encapsulated endings, capsule is very elongated, these are temperature receptors sensitive to hot stimuli.
Tendon spindles (GTO) Encapsulated spindle shaped endings found between tendon fibers to its junction w/ muscle. They act as stretch receptors to carry action potentials in relation to the tension of the associated muscle.
Interoceptors receptors in relation to visceral organs and blood vessels. They may be stimulated by mechanical or chemical stimuli.
Effectors nerves endings relaying motor impulses, that originate in the CNS to end organs like muslces or glands.
Somatic motor endings in relation to skeletal muscles are motor end plates, where motor terminal makes contact with skeletal fibers. terminal portion loses its myelin. it gives several branches each with a bulbous end which dips into the synaptic gutter.
Autonomic Motor endings occur in relation to smooth and cardiac muscles, and arise from autonomic plexuses in the walls of visceral organs. Motor fibers approach muscle fibers and wind around them to end terminally into bulbous endings over sarcolemma of muscle fibers.
Motor endings to glands arise from plexuses around acini of glands, the periacinar plexus. The endings control the secretory activity of the glands.
Lymphatic System primarily in immune defense of the body,contributes to phagocytic defense(reticuloendothelial system). Non-encapsulated-lyphatic tissue; Partially encapsulated lymphatic tissue(tonsils); Fully encapsulated lymphatic tissue (lymphatic organs);
Stroma fibrous framework is made up of reticular tissue; in Nodes Made up of: capsule, cortical & medullary trabeculae, Reticular tissue;
Parenchyma cellular component, composed of a collection of cells, mainly lymphocytes, occupying the meshes of reticular tissue. Lymphocytes, monocytes, histiocytes, plasma cells, lymph or blood sinusoids. Cortex: contains nodular L.T. forming Cortical nodules;
non-encapsulated lymph tissue in mucous membranes of digestive & respiratory tracts, & some visceral oragans.
Nodular lymphatic tissue round to oval collections of densely packed cells to form a nodule or follicle.Germinal center contains large lymphocytes and medium sized lymphocytes; outer zone of nodule is called cortex. Nodules maybe single or may form aggregates (Payer's Patches)
Diffuse lymph tissue dispersed loosely arranged cells of lymph tissue, usually occupies spaces btw nodules of lymphatic tissue.
Types of tonsils 2 palatine,, 1 lingual, 1 pharyngeal
Tonsillar crypts mucous membrane dips inside lymphatic tissue of tonsil to form tubular invaginations
Stratified squamous non-keratinized in palatine, and ligual tonsils;
Pseudo-stratified columnar ciliated with some goblet cells in pharyngeal tonsils.
Fully encapsulated lymph tissue lymphatic organs: lymph nodes, spleen, and thymus
Lymph nodes occur along lymph vessels(bean shaped w/ hilum) outer portion called cortex; inner zone called medulla.
Parenchyma: Medulla L.T. form irregular branching cords of densely arranged cells called medullary cods
Parenchyma:Lymph Sinuses made of subcapsular, cortical and medullary sinuses.
Circulation of Lymph Enters by afferent lymphatics(opposite of hilum) Lymph is received by subscapsular sinuses lying under capsule, passes then to cortical sinuses btw trabeculae and nodules, then to medullary sinuses, from there to efferent lymphatics; exits node at hilum
Thymus lies in superior & extend into anterior mediastinum; regress after puberty & replaced by adipose tissue.
Thymus Stroma: Contains Capsule, Trabeculae, and Cytoreticulum- not assoc. w/ reticular fibers, made up of branching cells attached together by epithelial-reticular cells, which secrete thymic factor(Thymosin) for development in immunological competent lymphocytes
Thymus Parenchyma Cortex: made up dense small lymphocytes called thymocytes or T-lymphocytes; Medulla: loosely arranged cells lymphocytes & some histiocytes; Hassalll's (Thymic) corpuscles are rounded lamellated acidophillic bodies-degenerating epithelial reticular cells
Spleen largest lymphatic organ in body; bllod & not lymph, circulates in its tissue: considered a hemal lymph node. (covered by peritoneum, w/ indentation of hilum where blood vessels enter and leave. Contains lights spots: white pulp; Reddish brown: red pulp.
Circulation of blood in spleen Slenic artery enters spleen at the hilum and splits to run in trabeculae (arteries) then enter splenic nodules as central arterioles. exits nodules as straight straight vessels called pencilli which pour into sinuses and drained after pulpvenules
Created by: AAbraham