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IdentifierNeuroKaplanLectureNotes. Identifier-arkark://t0jt50c1b. Ocr ABBYY FineReader Ppi ScannerInternet Archive HTML5. Kaplan USMLE Step 1 Lecture Notes Biochemistry and Medical Genetics # usmle #books #pdf #usmlebookspdf #step1 #step2 #step3 #usmlebooksonline. Anatomy (USMLE Prep) Kaplan Medical pdf, by Kaplan Medical USMLE Step 1 Lecture Notes Anatomy (USMLE Prep), book pdf USMLE Step 1 Lecture.
Type II Cells Type 11 cells are cuboidal—like cells that sit on the basal lamina of the epithelium and contain membrane-bound granules of phospholipid and protein lamellar bodies. Oligodendrocytes myelinate axons in the CNS. Aldosterone increases sodium and water reabsorption in the distal portion of the nephron. It makes it easy to scan through your lists and keep track of progress. Sperm Storage Sperm storage occurs in the efferent ductules, epididymis, and proximal ductus deferens. Contains granules that contain lysozyme. The ampulla gradually narrows to form the ejaculatory duct, which penetrates the prostate gland and empties into the urethra.
Kaplan Medical. Product Details. Kaplan Publishing December Length: Resources and Downloads. Anatomy eBook Get a FREE e-book by joining our mailing list today! More books from this author: See more by Kaplan Medical. More books in this series: Thank you for signing up, fellow book lover! See More Categories. Your First Name. Zip Code. Thank you! Anatomy 4 [AMA]! It contains three morphologically distinct zones: Chromatin Chromatin is a complex of DNA, histone proteins, and nonhistone proteins.
It exists in three conformations: They are important in forming two types of structures in chromatin: The nucleosomes are the basic repeating units of the chromatin fiber, having a diameter of approximately 10 nm. They are acidic or neutral proteins. They consist of large and small sub- units.
Ribosomes are assembled in the nucleus and transported to the cytoplasm through the nuclear pores. The large ribosomal subunits are synthesized in the nucleolus, whereas the small subunits are synthesized in the nucleus.
Forms of ribosomes Ribosomes exist in two forms: Rough endoplasmic reticulum RER is a single, lipid bilayer continuous with the outer nuclear membrane. RER synthesizes proteins that are destined for the Golgi apparatus, secretion. KER is very prominent in cells that are specialized in the synthesis of pro- teins destined for secretion e.
SER contains enzymes involved in the biosynthesis of phospholipids, triglycerides, and sterols. IAHIK 6 modlcal j: Ued with permission. Flgure I This controls the fonnation of free glucose from glycogen and via gluconeogencsis. The sequestration and release of calcium ions takes place in the SR. Anatomy Golgi Do not confuse the Golgi apparatus with the Golgi tendon organs of the cell or any other factor bearing his name.
Camillo Golgi was a prolific Italian histologist. Other structures or processes bearing his name include Go gi's silver stain for nerve cells, the cycle of Golgi for the development of the malaria parasite, the inhibitory Golgi cells of the cerebellum, and the acroblast, a part of the Golgi material of the spennatid known as the Golgi remnant.
Golgi Mitochondria Figure I This determines which proteins remain in the Golgi apparatus or leave the Golgi apparatus to become secretory proteins, lysosomal proteins, or part of the plasma membrane. Two diseases are caused by a.
Cell Components Clinical Correlate nnauu-. Hyperproinsulinemia is characterized by elevated levels of proinsulin in the serum resulting from the failure of a peptidase to cleave proinsulin to insulin and C- peptide in the Golgi apparatus. The clinical manifestations are similar to those seen in patients with noninsulin- dependent diabetes. I-Cell Disease Phosphorylation of mannose in glycoproteins targes proteins to lysosomes.
Phosphate is added in a two—step sequence of reactions that are catalyzed by N-acetylglucosamine-phosphotransferase and Nacetylgiucosaminidases. It is characterized by huge inclusion bodies in cells caused by the accumulation of undegraded glycoconjugates in lysosomes missing the hydrolases that normally degrade these macromolecules.
The missing enzymes are found in the plasma and other body fluids, where they have normal levels of activity. The absence of the mannose—5-phosphate on the hydrolases result in their secretion rather than their incorporation into lysosomes.
The disease results in skeletal abnormalities, coarse features, restricted joint movements, and psychomotor retardation. Symptoms are generally noted at birth, and the life span is less than 10 years.
A somewhat less severe form of the disease with a later onset and potential survival into adulthood is called pseudo—Hurler polydystrophy. There is no treatment for either disease, but prenatal diagnosis is available. Lysosomes Lysosomes are spherical rnembraneenclosed organelles that are approximately 0. Lysosomes consist of two forms: They are formed by budding from the trans side of the Golgi apparatus. These include nucleases for degrading DNA and RNA, lipases for degrading lipids, glycosidases for degrading glycoconjugates glyco- proteins, proteoglycans, and glycolipids , proteases and peptidases for degrading proteins, and a variety of phosphatases.
Figure I Lysosomes Peroxisomes Peroxisomes are a heterogeneous group of small, spherical organelles with a single membrane and a diameter that ranges from approximately 0. Peroxisomes contain a number of enzymes that transfer hydrogen atoms from organic sub- strates urate.
D-amino acids, and very long chain fatty acids to molecular oxygen with the for- mation of hydrogen peroxide. Catalase, the major pcroxisomal protein, degrades the hydrogen peroxide to water and oxygen. Pcroxisomal enzymes are synthesized on free polysomes. After translation, the enzymes are incorporated directly into peroxisomcs.
Peroxisomes have several functions: Oxidation of the residual 10 carbons is completed in the mitochondria. These patients tail to oxidize very long chain fatty acids and accumulate bile acid precursors. The four most common disorders are: AIIIighIs resolved. Figure IB. The Paroxlsome Mitochondria Mitochondria have two membranes. They are about 0.
They synthesize adenosine triphosphate ATP , contain their own double-stranded circular DNA, and make some of their own proteins.
Mitochondria have sev- eral compartments. Outer membrane The outer membrane is smooth, continuous, and highly permeable. The impermeability is likely related to the high con- tent of the lipid cardiolipin.
The cristae greatly increase the total surface area. It con- tains enzymes that use ATP to phosphorylate other nucleotides creatine phosphokinase and adenylate kinase. Cell Conlponenls Matrix The matrix is enclosed by the inner membrane and contains: I - A double-stranded circular DNA genome—encodcs a few of the mitocltonclrial pro- teins.
Mitochondrial DNA is always inherited from the mother, resulting in the mater- nal transmission of diseases of energy metabolism.
Their function is not known, but it is believed that they may represcltt a storage site for calcium. Cristae ' All ngms reserved. Figure l Microtubules Microtubules are polymers of tubulin that undergo rapid assembly and disassembly. They are found in the cytoplasmic matrix of all eukaryotic cells. This leads to defects in cytoptasmic granules including: Clinical Correlate Actin-binding drugs e. Processes such as endocytosis, phagocytosis, cytokinesis, and cytoplasmic and amoeboid movemens are all inhibited by cytochalasin B.
Polymerization of tubulin to form rnicrotubules is accomplished by microtubule organizing cen- ters and two types of accessory proteins, tau proteins and microtubule-associated proteins. Microtubules grow from the organizing centers. Calcium ions can block or reverse polymerization. Microtubules play a role in: Microtubule assembly is an important event in spindle formation. It consists of the following: These ridges of fission present!
It extends oomplctdyaronnd the apical cell borders to sea the underlying intercellular clefts from contact with the amide environment. It constitutes the anatomic component of many barriers in the body.
Cell Components Sealing Strands. Used with permission. Freeze-Fracture Replica of a Tight Junction Zonula adherens A zonula adherens adherent junction often lies basal to the zunula occludens Figure Desmosome The desmosome macula adhcrens is formed by the juxtaposition of two disk-shaped plaques contained within the cytoplasm of each adjacent cell Figure I All rights reserved.
Desmosome Gap junction The gap junction is an area of communication bclween adjacent cells that allows the passage of very small particles and ions across a small intercellular gap within the junction Figure I—l-I4.
The gap junction consists of a hexagonal lattice of tubular protein subunits called connexons, which form hydmphilic channels connecting the cytoplasm of adjacent cells Figure This permits the direct pssoge of ions and small molecules between cells to conduct electri- calimpulscs.
Used with permission Flgure l Anatomy Connexon Figure I Microvilli are apical cell surface evaginattons of cell membranes that function to increase the cell microvilli found at the apices. A thick glycocalyx coat covers them. Cell Components Cilia Cilia are apical cell siiriace projections of cell membrane that contain microtubules Figures l-l and I-l- I8.
They are inserted on ccntriole-like luisal bodies present below the mem- brane surface at the apical pole. Cilia contain two central microtubulcs surrounded by a circle of nine peripheral micro- tubule doublets. The peripheral doublets are fused so that they sliarc a common tubule wall and form two subtubules, A and B.
Adjacent doublets are connected to one another by nexin links Figure l-i— I8. The arms bind to ATP and rearrange themselves so that a binding site for the B subtubule in the tip of the arm is exposed. The B tubule interacts with the binding site, causing the arm to snap back and movement to occur.
Each cycle of a single dynein arm slides adjacent doublets 10 nm past each other. They are important in clearing mucus from the rmpiratory tract. T The Nucleus. The nucleus consists of a nuclear envelope, lamina, nucleolus and chromatin. Phosphorylation of the lamina during prophase of mitosis initiates nuclear disassembly into small vesicles. The nucleolus has a fibrillar ; center that contains nontranscribed DNA. Chromatin is a complex of DNA, histone, and nonhistone proteins. DNA exists in three forms: Histone proteins are positively charged and complex with DNA to form ; nucleosomes and solenoid fibers.
Nonhistone proteins are neutral and perform diverse functions such ' as DNA repair, replication, transcription, and regulation of chromatin function. There are two forms of chromatin: Ten percent of chromatin is in the form of heterochromatin.
The Barr body inactive X chromosome is heterochromatln. The cytoplasm The cytoplasm contains ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, mitochondria, and matrix. Ribosomes are composed of rRNA and protein.
Large ribosomal units are synthesized in the nucleolus, whereas small ones are synthesized in the nucleus. Polysomes are formed from ribosomes associating with a single mRNA strand. There are two kinds of polysomes: The former synthesize proteins destined for the nucleus, peroxisomes, or mitochondria. The latter form secretory proteins, lysosomal enzymes, and membrane proteins.
Endoplasmic reticulum exists in two forms: Smooth endoplasmic reticulum SER lacks ribosomes. It is involved in detoxification reactions—hydroxy ation, via cytochrome P, and conjugation. It forms glucose from glycogen via membrane—bound enzyme glucose—6 phosphatase and lipolysis by releasing fatty acid from triglyceride.
Other produas made here include phospholipids, lipoproteins, and sterols. SER in striated muscle is known as sarcoplasmic reticulum. Calcium ions are sequestered and released here. Rough endoplasmic reticulum RER contains ribosomes that synthesize proteins that are delivered to Golgi apparatus, lysosomes, and plasma membrane. Lysosomes are classified as primary or secondary.
The latter are formed by fusion of the former with either phagosomes or cellular organelles. Lysosomes contain approximately 60 hydrolyiic enzymes, all of which are acidic. Peroxisomes are organelles that synthesize and degrade hydrogen peroxide, initiate [3 oxidation of very long-chain fatty acids, synthesize bile and exchange of phospholipid. Mitochondria are organelles bounded by two membranes—an outer and inner membrane.
The inner membrane contains enzymes for electron transport and oxidative phosphorylation. Continued KAl'l. A l' medical 23 Thus, transmission of diseases of energy metabolism is from the mother. The Cytoskeleton is a supportive network that contains microtubules, intermediate filaments, and microfilaments.
Assembly of microtubules is important for spindle formation. Intermittent filaments contain tissue—specific proteins. Microfilaments are composed of actin. Cell Surface important cell surface modifications include the basal and reticular lamina, tight junctions, desmosomes, gap junctions, microvilli, and cilia. Cell Body The cell body contains a large vesicular nucleus with a single prominent nucleolus, mitochondria, and other organelles.
It has abundant RER, reflecting high rates of protein synthesis. At the light microscopic level, the RER stains intensely with basic dyes and is referred to as Nissl substance.
Dendrites Dendrites are neuronal processes that receive information and transmit it to the cell body. Extensive dendritic branching serves to increase the receptive area of the neuron. The cell membrane of the axon is called the axolemma, and the cytoplasm of the axon is called the axoplasm.
It proceeds in both anterograde and retrograde directions. Anterograde transport is powered by kinesins, whereas retrograde transport is powered by dynein. Synaptic boutons -Lxons terminate in specialized endings known as synaptic boutons, which contain synaptic vesicles full of neurotransmitter. Nervous Tissue Myelin Axons may be unmyelinated or myelinated. Unmyelinated Axons Unmyelinated axons in peripheral nerves are surrounded by the cytoplasm of Schwann cells.
Myelinated Axons Myelinated axons are larger in diameter and are ensheathed in myelin Figure l Schwann cells are the myelin-forming cells of the peripheral nervous system PNS. Myelination in the PNS begins during the fourth month of development. One Schwann cell will myelinzite only one axon in peripheral nerves. Oligodendrocytes are the myelimfonning cells of the central nervous system CNS.
An individual oligodendrocyte is able to myelinate many axons. Node of Ranvier At the junction between two myelin-producing cells. The action potential skips from node to node in a process called salte- tory conduction.
Myelinated axons conduct action potentials rapidly. Composition Because myelin is of membrane origin. Axons cut in Cross-Section Schwann Cell Nuclei Clinical Correlate The degeneration of oligodendrocytes results in many of the so-called demyelinating disorders, such as multiple sclerosis. Pseudounipolar neurons Pseudounipolar neurons Figure I have a single process close to the perikaryon, which divides into two branches.
One branch extends to a peripheral ending, and the other extends to the CNS. Pseudounipolar neurons are found in dorsal root ganglia and most cranial ganglia. Cell body Peripheral process Figure I Pseudounipolar Neurons Bipolar neurons Bipolar neurons have one axon and one dendrite. Bipolar neurons are found in the cochlear and Vestibular ganglia as well as in the retina and olfactory mucosa.
Multipolar neurons Multipolar neurons have one axon and multiple dendrites. Most neurons in the body are mul- tipolar e. Sensory neurons Sensory neurons receive sensory stimuli from the internal or external environment and relay them to the CNS. Synapses Synapses are specialized membrane junctions designed for the um'd. Location Synapses are either between an axon and a dcndritc axodcndritic; Figure I or between an axon and a cell body axosomatic.
Synapses between dendrites dendrodendritic and between axons axoaxonic also occur. Cleft Postsynoptic neuron Presynoptlc neuron Synaptic vesicles Figure l Anatomy 50 Wehical Synaptic vesicles Synapses contain synaptic vesicles. They consist of to um spherical or ovoid structures in the axoplasm that contain neurotransmitter e. Neurotransmitter is released into the synaptic cleft at the synapse when synaptic vesicles fuse with the presynaptic membrane.
Neuromuscular Junction The neuromuscular junction occurs at the motor end plate. It is the symapse between neurons and muscle cells Figure I ACh released from the axon depolarizes the sarcolemma via the acetylcholine nicotinic receptors.
It can be life threatening if swallowing or breathing is affected. These are replaced by l new receptors, which are manufactured by the Golgi apparatus and then inserted into the junctional folds. The normal half—life of a receptor is about 10 days. In myasthenia gravis, the half—life is reduced l to about 2 days, resulting in a marked decrease in the number of available receptors.
Administration of AChE inhibitors has both diagnostic and therapeutic value. By slowing the rate of ACh degradation, they increase the binding time of ACh to the remaining receptors. The usual response is prompt improvement in muscle power. Although they do not generate or transmit neural impulses, they play an important role in the normal func- tioning of the nervous system.
They form the myelin sheaths of axons and provide metabolic support to neurons. Neuroglia of the CNS include microglia, astrocytes, oligodendrocytes, and ependymal cells. In the PNS, neuroglia cells consist of Schwann cells.
Astrocytes Astrocytes are the largest of the neuroglial cells. They have centrally located nuclei and numer- ous long processes with expanded vascular end-feet, or pedicels, which attach to the walls of blood capillaries.
Astrocytes are important in controlling the microenvironment of nerve cells and participate in the maintenance of the blood—brain barrier. Oligodendrocytes Oligodendrocytes have small nuclei and contain abundant mitochondria, ribosomes, and microtubules. Oligodendrocytes myelinate axons in the CNS. Microglia Microglia are small, dense, elongated cells with elongated nuclei.
They originate from the meso- derm, unlike other neuroglial cells, which originate from the neuroectoderm. Microglia are phagocytic and are part of the mononuclear phagocyte system.
KAFll l' medical 31 Anatomy 32 Willical Ependymal Cells Ependymal cells line the ventricular cavities of the brain and the central canal of the spinal cord. They are capable of mitosis and can develop long processes that deeply penetrate the neural tissue. Schwann Cells Schwann cells contain elongated nuclei that lie parallel to the axons of peripheral neurons.
Schwann cells myelinate peripheral axons. Chapter Summary Neurons are composed of a cell body, dendrites, and an axon.
They contain pigments such as melanin and lipofuscin. The cell body soma or perikaryon contains a nucleus, other cellular components, and rough endoplasmic reticulum. Microtubules and neurofilaments form the cytoskeleton. They are important for axonal transport. Dendrites receive and transmit information to the cell body. Axons arise from the perikaryon or proximal dendrite.
They contain microtubules and neurofilaments. Rapid axonal transport utilizes microtubules. Kinesins promote anterograde transport, whereas dynein promotes retrograde transport. Myelin is the covering of axons and is composed of phospholipids and cholesterol.
Axons maybe myelinated or nonmyelinated. Schwann cells myelinate a single peripheral nervous system axon.
Oligodendrocytes form myelin in the central nervous system. One oligodendrocyte myelinates many axons. The node of Ranvier is a collar of naked axon between a proximal and distal bundle of myelin that has myelinated the axon. This process is called saltatory conduction.
Some general features of all three types of muscle are summarized in Table I Table I Note the three levels of connective tissue: In the center of the A band a paler region, the H band, is seen in relaxed muscle. These bands and the Z lines are well demonstrated in electron micrographs of skeletal muscle Figure I The sarcomeres are the basic units of contraction of striated muscle. Myosin is a molecule that contains a tail and two heads. Sarcomere Structure These invaginations constitute the transverse T tubule system Figure I Note the following: These and other differences are summarized in Table I Bands of smooth muscle cells can be found in the erector pili muscles of the skin.
Klflllf medical 37 Anatomy Table Contraction Smooth muscle contraction may be triggered by various stimuli such as autonomic nerves or hormones. Muscle Tissue i Muscles are classified as skeletal, cardiac, or smooth. General features are summarized in Table Skeletal Muscle: Skeletal muscle has three levels of connective tissue: Skeletal muscle is composed of long cylindrical fibers that have dark A bands and light I bands.
Skeletal muscle fibers contain myofibrils, which i in turn are composed of sarcomeres. Thick filaments are centraliy located in sarcomeres, where they interdigitate with thin filaments. Thin filaments contain three proteins: Actin forms a double helix, whereas tropomyosin forms an oi—helix. Troponin includes three polypeptides: TnT, which binds to tropomyosin; TnC, which binds to calcium ions; and Tnl, which inhibits actin—myosin interaction. Myosin has two heavy chains with globular head regions.
The heads contain actin-binding sites and have ATPase activity. The transverse tubular system surrounds each myofibril and facilitates excitation-contraction coupling. Cardiac Muscle Cardiac muscle has an arrangement of sarcomeres similar to that in skeletal muscles, but the fibers are coupled through gap junctions. Smooth muscle is found in the walls of blood vessels and hollow viscera.
Gap junctions couple them electrically.
Electrical or chemical signaling via hormones can i trigger smooth muscles. Table l—3—2 summarizes the differences between the three types of muscles.
The thymus contains epithelial reticular cells and Hassall corpuscles in the medulla and lacks germinal centers. The thymus protects developing T cells by the blood—thymus barrier that consists of a capillary wall. It is populated by most of the B lymphocytes. High Endothelial Venules High endothelial Venules form the site of repopulation of lymph nodes and are found in the paracortical zone.
Lymph Node SPLEEN The spleen has an extensive blood supply consisting of trabecular arteries, central arteries, peni- cillar arteries, sinusoids, red pulp veins, and trabecular veins. It is surrounded by a capsule, has trabeculae, and is divided into red and white pulp Figure I White Pulp White pulp consists of lymphoid tissue that ensheaths the central arteries periarterial sheath along with the associated nodules and germinal centers.
The periarterial sheath is populated mainly by T lymphocytes. The peripheral white pulp and germinal centers are populated mainly by B lymphocytes. Red Pulp Red pulp consists of splenic cords of Billroth and venous sinusoids. Defective red blood cells resulting from aging or disease as in sickle cell anemia, hereditary spherocytosis, or thalassemia syndromes are delayed in their passage from Billroth cords into the venous sinusoids and phagocytosed by macrophages lining the cords.
Lymphoid Organs Trabecular artery t? Peripheral Mg. Epithelial reticular cells and Hassall's corpuscles are located within the medulla. The cortex lacks germinal centers. The thymus protects developing T cells by the blood—thymus barrier. The lymph node has three layers: The outer cortical layer contains most of the nodules and germinal centers. Most of the B lymphocytes reside here, whereas T lymphocytes reside in the paracortical layer.
High endothelial Venules are the site of repopulation of lymph E nodes and are located within the paracortical zones.
The spleen is very vascular and has red and white pulp. White pulp is composed of lymphoid tissue. Red pulp consists of splenic cords and venous sinusoids. Its function l is to delay passage ol defective red blood cells to enable their elimination through phagocytosis by l macrophages. It is considered to be the largest organ in the body.