Kaplan - Anatomy, Histology, Embriology Lecture Notes 2001 (pdf document) free file download at fliiby.com

"GetPedia Table of Contents Preface ix ANATOMY I. HISTOLOGY AND CYTOLOGY 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Cell Components Nervous Tissue Muscle Tissue Lymphoid Organs Integument Respiratory System Gastrointestinal System Renal/Urinary System Male Reproductive System Female Reproductive System 3 25 35 41 45 49 55 65 73 81 II. EARLY EMBRYOLOGY 1. 2. 3. 4. Gonad Development Week 1: Beginning of Development Week 2: Formation of the Bilaminar Embryo Embryonic Period (Weeks 3-8) 93 .97 99 101 KAPLAN MEDICAL III. GROSS ANATOMY AND ORGANOGENESIS 1. 2. 3. 4. 5. 6. Back and Nervous System Thorax Abdomen, Pelvis, and Perineum Upper Limb Lower Limb Head and Neck 107 119 155 205 217 231 IV. NEUROSCIENCE 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. Peripheral Nervous System Central Nervous System The Ventricular System The Spinal Cord The Brain Stem The Cerebellum Visual Pathways Diencephalon Basal Ganglia Cerebral Cortex The Limbic System 277 283 289 293 315 351 359 365 371 377 395 PHYSIOLOGY I. GENERAL TOPICS 1. Membrane Transport 2. Body Compartments 405 415 II. EXCITABLE TISSUE 1. Ionic Equilibrium and Resting Membrane Potential 2. The Neuron Action Potential 3. Synaptic Transmission 441 455 463 III. PERIPHERAL CIRCULATION 1. General Aspects of the Cardiovascular System 2. Regulation of Blood Flow and Pressure 487 513 Vi KAPLAN MEDICAL IV. SKELETAL MUSCLES 1. Excitation-Contraction Coupling 2. Skeletal Muscle Mechanics V. CARDIAC MUSCLE 1. Electrical Activity of the Heart 2. Heart Muscle Mechanics 553 563 589 603 VI. RESPIRATION 1. Lung Mechanics 2. Alveolar-Blood Gas Exchange 3. Transport of O2 and CO2 and the Regulation of Respiration 4. Four Causes of Hypoxemia VII. RENAL PHYSIOLOGY 1. Renal Processes 2. Clearance 3. Regional Transport VIII. ACID-BASE DISTURBANCES IX. ENDOCRINOLOGY 1. Mechanism of Hormone Action 2. The Hypothalamic-Anterior Pituitary System 3. Adrenal Hormones 4. Antidiuretic Hormone (ADH) and Regulation of Osmolarity and Extracellular Fluid (ECF) 5. The Endocrine Pancreas 6. Growth Hormone 7. Adrenal Medulla 8. Hormonal Control of Calcium and Phosphate 9. Thyroid Hormones 10. Male Reproductive System 11. Female Reproductive System X. GASTROINTESTINAL PHYSIOLOGY 649 673 681 697 733 751 757 797 815 821 825 851 857 871 879 883 895 909 919 963 KAPLAN M E D I C A L Preface These three volumes of Lecture Notes represent a yearlong effort on the part of the Kaplan Medical faculty to update our curriculum to reflect the most-likelyto-be-tested material on the current USMLE Step 1 exam. Please note that these are Lecture Notes, not review books! The Notes were designed to be accompanied by faculty lectures—live, on video, or on the web. Reading these Notes without accessing the accompanying lectures is not an effective way to review for the USMLE. To maximize the effectiveness of these Notes, annotate them as you listen to lectures. To facilitate this process, we've created wide, blank margins. While these margins are occasionally punctuated by faculty high-yield "margin notes," they are, for the most part, left blank for your notations. Use them!! Many students find that previewing the Notes prior to the lecture is a very effective way to prepare for class. This allows you to anticipate the areas where you'll need to pay particular attention. It also affords you the opportunity to map out how the information is going to be presented and what sort of study aids (charts, diagrams, etc.) you might want to add. This strategy works regardless of whether you're attending a live lecture or watching one on video or the web. Finally, we want to hear what you think. What do you like about the notes? What do you think could be improved? Please share your feedback by E-mailing us at medfeedback@kaplan.com. Thank you for joining Kaplan Medical, and best of luck on your Step 1 exam! Kaplan Medical KAPLAN MEDICAL IX USMLE Step 1 Anatomy (Histology, Embryology, Gross Anatomy, and Neuroscience) medical KAPLAN.. _ SECTION I Histology and Cytology Cell Components 1 MA/ NUCLEUS The nucleus (Fig 1-1-1) is the site of deoxyribonucleic acid (DNA) replication and transcription of DNA into precursor ribonucleic acid (RNA) molecules. It contains all of the enzymes required for replication and repair of newly synthesized DNA, as well as for transcription and processing of precursor RNA molecules. It is enclosed by the nuclear envelope and contains the nuclear lamina, nucleolus, and chromatin. Nuclear Envelope The nuclear envelope is a double membrane containing pores that are approximately 90 nm in diameter. The outer nuclear membrane is continuous with the endoplasmic reticulum. Nuclear Lamina The nuclear lamina is a latticelike network of proteins that include larnins. H<amins}rttach qfcromatin to the inner membrane of the nuclear envelope and participate in the breakdown and reformation of the nuclear envelope during the cell cycle. Phosphorylation of the lamina (by lamin kinase) during nronhase of mitosis initiates nuclear disassembly into small vesicles. KAPLAN MEDICAL USMLE Step 1: Anatomy Nucleolus The nucleolus is responsible for ribosomal RNA (rRNA) synthesis and ribosome assembly. It contains three morphologically distinct zones: • Granular zone—found at the periphery; contains ribosomal precursor particles in various stages of assembly. • Fibrillar zone—centrally located; contains ribonuclear protein fibrils. • Fibrillar center—contains DNA that is not being transcribed. Chromatin Chromatin is a complex of DNA, histone proteins, and nonhistone proteins. • DNA—a double-stranded helical molecule that carries the genetic information of the cell. It exists in three conformations: B DNA, Z DNA, and A DNA. • Histone proteins—positively charged proteins enriched with lvjsine and arginine residues. They are important in forming two types of structures in cnTomatinrflucIeoso^ies and solenoid fibers. The nucleosomes are the basic repeating units of the chromatin fiber, having a diameter of approximately 10 nm. • NojJiisJtonej>roteins—include enzymes involved in nuclear functions such as replication, transcription, DNA repair, and regulation of chromatin function. They are acidic or neutral proteins. Forms of Chromatin (Fig 1-1-1) • Heterochromatin—highly condensed (30-nm solenoid fibers or higher states of condensation) and transcriptionally inactive. In a typical eukaryotic cell, approximately 10% of the chromatin is heterochromatin. Almost the entire inactive jLchromosome (Barr_body) in each somatic cell in a woman is condensed Into heterochromatin. • Euchromatin—a more extended form of DNA, which is potentially transcriptionally active. In a typical cell, euchromatin accounts for approximately 90% of the total chromatin, although only about 10% is being actively transcribed in the 10-nm fiber of nucleosomes. KAPLAN M E D I C A L Cell Components Euchromatin Heterochromatin Nucleolus Figure 1-1-1. Nucleus CYTOPLASM ) RRibosomes I Ribosomes are composed of rRNA and protein. They consist of large (60S) and small (40S) subunits. Rihpsorn£s are assembled in the nucleus and transported to the cytoplasm through the nuclear pores. The large ribosomal subunits are synthesized in the nucleolus, whereaTthe small subunits are synthesized in the nucleus. • Polysomes—Ribosomes often form polysomes, which consist of a single messenger RNA (mRNA) that is being translated by several ribosomes at the same time. The ribosomes move on the mRNA from the 5' end toward the 3' end. The two ribosomal subunits associate on the mRNA, with the small subunit binding first. Forms of Ribosomes Ribosomes exist in two forms: • Free polysomes are the site of synthesis for proteins destined for the nucleus, peroxisomes, or mitochondria. • Membrane-associated polysomes are the site of synthesis of secreto proteins, membrane proteins, and lysosomal enzymes. v Endoplasmic Reticulum The endoplasmic reticulum exists in two forms, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). KAPLAN MEDICAL USMLE Step 1: Anatomy Rough Endoplasmic Reticulum RER is a single, lipid bilayer continuous with the outer nuclear membrane. It is organized into stacks of large flattened sacs called cisternae that are studded with ribosomes on the cytoplasmic side (Fig 1-1-2). RER synthesizes proteins that are destined for the Golgi apparatus, secretion, the plasma membrane, and lysosomes. RER is very prominent in cells that are specialized in the synthesis of proteins destined for secretion (e.g., pancreatic acinar cells). Copyright 2000 Gold Standard Multimedia, Inc. All rights reserved. Figure 1-1-2. Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum SER is a network of membranous sacs, vesicles, and tubules continuous with the RER, but lacking ribosomes (Fig 1-1-3). SER contains enzymes^ involved in the biosynthesis of phospholipids, triglycerides, and sterols. it w KAPLAN MEDICAL Cell Components •/ Image copyright 1984 Lippincott Williams & Wilkins. Used with permission. Figure 1-1-3. Human Corpus Luteum of Pregnancy Functions of SER Detoxification Reactions These are reactions that make compounds water soluble so that they can be excreted. Two types of reactions that increase solubility are: 1 Hydroxylation reactions—by way of hydroxylase complexes containing cytochrome P450, a flavoprotein, and a nonheme iron protein • Conjugation reactions—the transfer of polar groups (i.e., glucuronic acid) from the active carrier UDPglucuronic acid to the toxic water-insoluble molecule Glycogen Degradation and Gluconeogenesis Removal of the phosphate group from glucose-6-phosphate by the enzyme glucose-6 phosphatase, an integral membrane protein of the SER. This controls the formation of free glucose from glycogen and via gluconeogenesis. ^x /"*#< Reactions in Lipid Metabolism Lipolysis begins in the SER with the release of a fatty acid from triglyceride. The SER is also the site where lipoprotein_ KAPLAN M E D I C A L USMLE Step 1: Anatomy Sequestration and Release of Calcium Ions In striated muscle the SER is known as the sarcoplasmic reticulum (SR). The sequestration and release of calcium ions takes place in the SR. Golgi Do not confuse the Golgi apparatus with the Golgi tendon organs of the cell or any other factor bearing his name. Dr. Camillo Golgi was a prolific Italian histologist. Other structures or processes bearing his name include Golgi'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 spermatid known as the Golgi remnant. Golgi Apparatus The Golgi apparatus consists of disc-shaped smooth cisternae that are assembled in stacks (dictyosomes), having a diameter of approximately 1 |xm and associated with numerous small membrane-bound vesicles (Fig 1-1-4). Mitochondria Figure 1-1-4. Cytoplasm The Golgi apparatus has two distinct faces: • The cis (forming) face is associated with the RER. • The trans (maturing) face is often oriented toward the plasma membrane. The trans-most region is a network of tubular structures known as the trans-Golgi network (TGN) (Fig 1-1-5). KAPLAN MEDICAL Cell Components Plasma Membrane Clinical Correlate Hyperproinsulinemia ^ Secretory/ \ y Condensing Vacuole 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 noninsulindependent diabetes. Transitional Element RER Figure 1-1-5. Golgi Apparatus Functions of the Golgi Apparatus Proteins and Lipids jolgi apparatuses the site of posttranslational modification and sorting of iesize3 proteins and lipids. Glycoproteins Further modification of the carbohydrate moiety of glycoproteins produces complex and hybrid oligosaccharide chains. 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 breakdown in this process, I-cell disease and hyperproinsulinemia (see related box and margin note). /I / 0 -> KAPLAN MEDICAL USMLE Step 1: Anatomy Clinical Correlate I-Cell Disease Phosphorylatlon of mannose in glycoproteins targets proteins to lysosomes. Phosphate is added in a two-step sequence of reactions that are catalyzed by —(-IV-acetylglucosamine-phosphotransferase and N-acetylglucosaminidases. A deficiency in N-acetylglucosamine-phosphotransferase results in l-cell disease (mucolipidosis II), in which a whole family of enzymes is sent to the wrong destination. It is characterized by huge inclusion bodies in cells caused by the accumulation of undegraded glycoconjugates in lysosomes missing the hydrclases 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-6-phosphate on the hydrolases results 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 membrane-enclosed organelles that are approximately 0.5 fxm in diameter and contain enzymes required for intracellular digestion (Fig 1-1-6). Lysosomes consist of two forms: /• Primary lysosomes have not yet acquired the materials to be digested. They are formed by budding from the tramssirle_of thp Hnlgi Secondary lysosomes are formed by the fusion of the primary lysosome with the substrate to be degraded and have contents that are in various stages of degradation. Lysosomes contain approximately 60 hydrolytic enzymes. These include nucleases for degrading DNA and RNA, lipases for degrading lipids, glycosidases for degrading glycoconjugates (glycoproteins, proteoglycans, and glycolipids), proteases and peptidases for degrading proteins, and a variety of phosphatases. • All lysosomal enzymes are acid hydrolases, with optimal activity at a pH Qf approximately 5.0. • The synthesis of the lysosomal hydrolases occurs in the RER; the hydrolases are transferred to the Golgi apparatus, where they are modified and packaged into lysosomes. 1 10 KAPLAN MEDICAL Cell Components Clinical Correlate Peroxisome Deficiency Several genetic diseases are associated with the impairment or absence of peroxisomes. These patients fail to oxidize very long chain fatty acids and accumulate bile acid precursors. The four most common disorders are: • Zellweger (cerebrohepatorenal) syndrome • Neonatal adrenoleukodystrophy • Infantile Refsum disease • Hyperpipecolatemia Copyright 2000 Gold Standard Multimedia, Inc. All rights reserved. Figure 1-1-6. Lysosomes Peroxisomes Peroxisomes are a heterogeneous group of small, spherical organelles with a single membrane and a diameter that ranges from approximately 0.15 to 0.5 |xm (Fig 1-1-7). Peroxisomes contain a number of enzymes that transfer hydrogen atoms from organic substrates (urate, D-amino acids, and very long chain fatty acids) to molecular oxygen with the formation of hydrogen peroxide. ^ataRfee, the major peroxisomal protein, degrades the hydrogen peroxide to water and oxygen. Peroxisomal enzymes are synthesized on free polysomes. After translation, the enzymes are incorporated directly into peroxisomes. Peroxisomes have several functions: • Synthesis and degradation of hydrogen peroxide ^ • 3-Oxidation of very long chain fatty acids (> C24) starts in the peroxisome ,/\ and proceeds until the carbon chain has been reduced to a length of approximately 10 carbons. Oxidation of the residual 10 carbons is completed in the mitochondria. • Phospholipid exchange—peroxisomes contain enzymes that convert phosphatidylserine and phosphatidylethanolamine. • Bile acid synthesis \J J P5 KAPLAN MEDICAL 1 USMLE Step 1: Anatomy Mitochondria Peroxisome Copyright 2000 Gold Standard Multimedia, Inc. All rights reserved. Figure 1-1-7. The Peroxisome Mitochondria Mitochondria have two membranes with a width of about 0.5 u,m, and a length that can vary from 1 to 10 |xm (Fig 1-1-8). They synthesize adenosine triphosphate (ATP), contain their own double-stranded circular DNA, and make some of their own proteins. Mitochondria have several compartments. Outer Membrane The outer membrane is smooth, continuous, and ]jiglily_p_errn£able. It contains an abundance of^orir^an integral membrane protein that forms channels in the outer membrane through which molecules of less than LQ,kD can pass. Inner Membrane The inner membrane is impermeable to most small ions (Na+, K+, H + ) and small molecules (ATP, adenosine diphosphate, pyruvate). The impermeability is likely related to the high content of the lipid cardiolipin. ~ —i • The inner membrane has numerous infoldings, called cristae. The cristae greatly increase the total surface area. They contain the enzymes for electron transport and oxidative phosphorylation. • The number of mitochondria and the number of cristae per mitochondrion are proportional to the metabolic activity of the cells in which they reside. Intermembrane Compartment The intermembrane compartment is the space between the inner and outer 12 KAPLAN MEDICAL Cell Components membranes. It contains enzymes that use ATP to phosphorylate other nucleotides (creatine phosphokinase and adenylate kinase). Matrix The matrix is enclosed by the inner membrane and contains: y^irogena^es—oxidize many of the substrates in the cell (pyruvate, aminoacids, tatty acids), generating reduced nicotinamide adenine dinucleotide (NADH) and reduced flavin adenine dinucleotide (FADH2) for use by the electron transport chain and energy generation. ~"""=~" • A double-stranded circular DNA genome—encodes a few of the mitochondrial proteins. Mitochondrial DNA is always inherited from the mother, resulting in the maternal transmission of diseases of gnerffy metabolism. • RNA, proteins, and ribosomes—although there is some protein synthesis, most mitochondrial proteins are synthesized in the cytoplasm and are transferred into the mitochondria. 1 Intramitochondrial granules—contain calcium and magnesium. Their function is not known, but it is believed that they may represent a storage site for calcium. Cristae Copyright 2000 Gold Standard Multimedia, Inc. All rights reserved. Figure 1-1-8. Mitochondria CytoskeiefoiP) Thecytoskele^n_grpvides a supportive network of tubules and filaments in the cytoplasm of eukaryotic cells. It is composed of microtubules, intermediate filaments, and microfilaments. KAPLAN MEDICAL 13 USMLE Step 1: Anatomy Clinical Correlate Chediak-Higashi syndrome Chediak-Higashi syndrome is characterized by a defect in microtubule polymerization. This leads to defects in cytoplasmic granules including: • Delayed fusion of phagosomes with lysosomes in leukocytes, thus preventing phagocytosis of bacteria. • Increased fusion of melanosomes in melanocytes, leading to albinism. • Granular defects in natural killer cells and platelets. Microtubules Microtubules are polymers of tubulin that undergo rapid assembly and disassembly. They are found in the cytoplasmic matrix of all eukaryotic cells. Tubulin The major component of microtubules is tubulin, a protein dimer composed of two different polypeptides, a-tubulin and J3-tubulin. Polymerization of tubulin to form microtubules is accomplished by..."

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