Review Questions

Ultrasound imaging reveals a fetus that has spina bifida cystica with meningomyelocele. What else might be expected (A) Higher than predicted levels of alpha-fetoprotein in amnionic fluid (E) A tuft or hair in skin over the defect 2. Polyhydramnios is evident during a pregnancy. What might ultrasound imaging reveal in the fetus 3. A newborn infant presents with several vertebrae that lack spinous processes and a cyst covered by meninges protruding through the defect. What fluid will the cyst...

J Uterine Wall

The endometrium is composed of simple columnar epithelium (ciliated and nonciliated cells), with two layers The deeper basal layer is relatively thin and is not discharged during menstruation. i The superficial functional layer alters during the menstrual cycle and is lost at men- The myometrium is composed of smooth muscle, connective tissue, and prominent blood vessels. The perimetrium consists of the peritoneal layer of the broad ligament.

Skeletal Elements Vertebrae

The vertebrae have facets on their bodies to articulate with the heads of ribs each rib head articulates with the body of the numerically corresponding vertebra and the one below it The thoracic vertebrae have facets on their transverse processes to articulate with the tubercles of the numerically corresponding ribs.

Hepatic portal system

GI tract veins to liver sinusoids to hepatic veins (Figure III-3-36). The hepatic portal vein is formed by the union of the superior mesenteric and splenic veins (posterior to the neck of the pancreas). The inferior mesenteric vein enters near the area of the junction of the superior mesenteric and splenic veins. The hepatic portal vein also receives gastric veins from the stomach. The portal vein drains into the liver sinusoids, which drain to the hepatic vein, which then goes into the...

Right ventricle

The right ventricle receives blood from the right atrium via the tricuspid valve outflow is to the pulmonary trunk via the pulmonary semilunar valve. The trabeculae carneae are ridges of myocardium in the ventricular wall. Papillary Muscles The papillary muscles project into the cavity of the ventricle and attach to cusps of the AV valve by the strands of the chordae tendineae. The chordae tendineae control closure of the valve during contraction of the ventricle. Infundibulum The infundibulum...

Medical

USMLE is a joint program of the Federation of State Medical Boards of the Unrted States. Inc. and the National Board of Medical Examiners. All rights reserved. No part of this book may be reproduced in any form, by photostat, microfilm, xerography or any other means, or incorporated into any information retrieval system, electronic or mechanical, without the written permission of Kaplan, Inc. Professor of Neuroscience and Cell Biology Associate Dean for Admissions and Student Affairs UMDNJ...

Transversalis fascia

The transversalis fascia lines the abdominal cavity. It forms the posterior layer of the rectus sheath below the arcuate line and the internal spermatic fascia of the spermatic cord. The deep inguinal ring begins as an outpouching of transversalis fascia just lateral to where the inferior epigastric vessels intersect the inguinal ligament. The transversalis fascia is separated from the peritoneum by a layer of fatty areolar connective tissue. Figure 111-3-3. Layers of Anterolateral Abdominal...

Aorticopulmonary Septum

NeuraJ crest ceUsrnigrate into the truncal and bulbar ridges, which grow in a spiral fashion and fuse to form the aorticopulmonary (AP) septum. The AP septum divides the truncus arteriosus into the aorta and pulmonary trunk (Figure III-2-9). Figure 111-2-9. Formation of the Aorticopulmonary Septum Transposition of the great vessels occurs when the AP septum fails to develop in a spiral fashion and results in the aorta opening into the right ventricle and the pulmonary trunk opening into the...

Summary

Some of the principal ultrastructural features of the three types of muscle are summarized in Table 1-3-2. Table 1-3-2. Ultrastructure Comparison of the Three Types of Muscle Table 1-3-2. Ultrastructure Comparison of the Three Types of Muscle Overlapping actin and myosin filaments, forming a characteristic banding pattern Overlapping actin and myosin filaments, forming a characteristic banding pattern Actin and myosin do not form a banding pattern T tubules form triadic contacts with SR at A-I...

Lumbar origin

Two crura each crus takes its origin from the bodies of the upper two (left) or three (right) lumbar vertebral bodies. Medial arcuate ligament a thickening of the deep fascia covering the anterior surface of the psoas major. Some muscle of the diaphragm arises from this thickening. Lateral arcuate ligament a thickening of the deep fascia covering the anterior surface of the quadratus lumborum. Some muscle of the diaphragm arises from this thickening.

Tuberal region

Cells in the arcuate nucleus produce releasing hormones and inhibitory factors, which enter capillaries in the tuberoinfundibular tract and pass through the hypophyseal-portal veins to reach the secondary capillary plexus in the anterior pituitary gland. Releasing hormones and inhibitory factors influence the secretory activity of the acidophils and basophils in the anterior pituitary. (See Histology section.) The ventromedial hypothalamus is a satiety center and regulates food intake. Lesions...

Blood Supply

The cortex is supplied by the two internal carotid arteries and the two vertebral arteries (Figures IV-10-4 and IV-10-5). On the base (or inferior surface) of the brain, branches of the internal carotid arteries and the basilar artery anastomose to form the circle of Willis. The anterior part of . the circle lies in front of the optic chiasm, whereas the posterior part is situated just below the mammillary bodies. The circle of Willis is formed by the terminal part of the internal carotid...

Ventral Horn

The ventral horn contains alpha and gamma motoneurons. The alpha motoneurons innervate skeletal muscle (extrafusal fibers) byway of a specialized synapse at a neuromuscular junction, and the gamma motoneurons innervate the contractile intrafusal muscle fibers of the muscle spindle. Within the ventral horn, alpha and gamma motoneurons that innervate flexors are dorsal to those that innervate extensors. Alpha and gamma motoneurons that innervate the proximal musculature are medial to those that...

Knee Joint

Structures of the Ankle Figure 111-5-6. Structures of the Ankle There are three anklebone joints the talocrural joint, the subtalar joint, and the transverse tarsal joint. The talocrural joint is formed by the distal ends of the tibia and fibula and the talus. The movements at this joint are dorsiflexion and plantar flexion. The medial collateral (deltoid) ligament and the lateral collateral ligament prevent abduction and adduction, respectively. These are the ligaments commonly...

Muscles

The quadratus lumborum extends upward from the iliac crest to the inferior border of the 12th rib. It stabilizes the 12th rib during inspiration. The psoas major arises from the transverse processes of the lumbar vertebrae. Insertion, along with iliacus, is on die lesser trochanter of the femur. It is the chief flexor of the hip. The iliacus originates from the iliac fossa. It joins with the psoas major to insert on the lesser trochanter. Together with psoas major, it is known as the iliopsoas....

Answers and Explanations

Oligodendrocytes form myelin for all myelinated axons inside the CNS, including tracts in the white matter of the spinal cord. 2. Answer E. The patient has a combination of upper and lower motor neurons signs characteristic of ALS. In this case, the ALS has affected the cervical enlargement first resulting in lower motor neurons signs in the upper limbs and upper motor signs in the lower limbs. 3. Answer E. A ventral root contains axons of lower motor neurons and is found in the...

Visual cortex

The visual cortex is divided into striate (area 17) and extrastriate (areas 18 and 19). Area 17, also referred to as the primary visual cortex, lies on the medial portion of the occipital lobe on either side of the calcarine sulcus. Its major thalamic input is from the lateral geniculate nucleus. Some input fibers are gathered in a thick bundle that can be visible on the cut surface of the gross brain, called the fine of Gennari. The retinal surface (and therefore the visual field) is...

Prefrontal cortex

The prefrontal cortex is located in front of the premotor area and represents about a quarter of the entire cerebral cortex in the human brain. This area is involved in organizing and planning the intellectual and emotional aspects of behavior, much as the adjacent premotor cortex is involved in planning its motor aspects. The frontal eye field lies in front of the motor cortex in 8rodmann area 8. This cortical area is the center for contralateral horizontal gaze. A lesion here results in an...

Preface

These seven volumes of Lecture Notes represent a yearlong effort on the part of the Kaplan Medical faculty to update oar curriculum to reflect the most-likely-to-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...

Spleen

The spleen develops in the dorsal mesentery of the stomach (dorsal mesogastriurn). The spleen arises from cells of the mesentery, which migrate into the plane between the layers of the mesentery. The mesentery covering tbe spleen becomes the visceral peritoneum of the spleen. The mesentery between the spleen and the gut tube becomes the gastrosplenic ligament. The mesentery between the spleen and the dorsal body wall becomes the splenorenal ligament (most of which subsequendy fuses to become...

Pericardium

The pericardium has an outer fibrous sac and a double-layered serous membrane that encloses the pericardial cavity between its parietal and visceral layers. The transverse pericardial sinus is a space posterior to the ascending aorta and pulmonary trunk and anterior to the superior vena cava and left atrium. The oblique pericardia sinus is a blind, inverted, U-shaped space posterior to the heart and bounded by reflection of serous pericardium around die four pulmonary veins and the inferior...

Smooth Muscle

Smooth muscle is found in the walls of blood vessels and hollow viscera. Bands of smooth muscle cells can be found in the erector pili muscles of the skin. Gap junctions electrically couple smooth muscle cells. Smooth muscles contain actin and myosin filaments, but the filaments are not arranged in orderly arrays as in skeletal muscle. Bundles of myofilaments course obliquely in the cell, forming a lattice-like arrangement. A sliding filament mechanism of contraction is thought to occur. Thin...

Pancreas

The ventral pancreatic diverticulum becomes the major pancreatic duct (of Wirsung), and the dorsal pancreatic diverticulum becomes the minor pancreatic duct (of Santorini) (Figures III-3-13 and III-3-14). The inferior portion of the head of the pancreas and the uncinate process develop from the ventral bud, and the superior portion of the head and the neck, body, and tail of the pancreas develop from the dorsal bud. Most of the pancreas is secondarily retroperitoneal, but the distal part of the...

Muscles of Mastication

There are four major muscles of mastication the masseter, temporalis, lateral pterygoid, and medial pterygoid. Ail but the masseter lie in the infratemporal fossa. The masseter, temporalis, and medial pterygoid muscles elevate the mandible. The lateral pterygoid depresses and protrudes the mandible. The medial and lateral pterygoids protrude the mandible when they contract together and deviate the mandible from side to side in a grinding motion. The anterior belly of the digastric and the...

Cranial Nerves V Vi Vii and VIII

Four cranial nerves emerge from the pons. Cranial nerves VI, VII, and VIII emerge from the pon-tomedullary junction. The facial nerve is located medial to the vestibulocochlear nerve. The abducens nerve (CN VI) emerges near the midline lateral to the corticospinal tract. The trigeminal nerve (CN V) emerges from the middle of the pons. The midbrain (mesencephalon) is located between the pons and diencephalon. The cerebral aqueduct, a narrow channel that connects the third and fourth ventricles,...

Left atrium

The left atrium receives oxygenated blood from the lungs via the pulmonary veins. There are four openings the upper right and left and the lower right and left pulmonary veins. The left AV orifice is guarded by the mitral (bicuspid) valve it allows oxygenated blood to pass from the left atrium to the left ventricle. Blood enters from the left atrium through the mitral valve and is pumped out to the aorta through the aortic valve. The trabeculae carneae, or ridges of myocardium in the...

Frontal Lobe

A large part of the frontal cortex rostral to the central sulcus is related to the control of movements, primarily on the opposite side of the body. These areas include primary motor cortex (Brodmann area 4), premotor cortex (area 6), the frontal eye field (area 8), and the motor speech areas of Broca (area 44 and 45). Traditionally, area 4 is considered the primary motor cortex. It is in the precentral gyrus, immediately anterior to the central sulcus, and contains an orderly skeletal motor...

Implantation

The zona pellucida must degenerate for implantation to occur. The blastocyst usually implants within the posterior wall of the uterus. The embryonic pole of blastocyst implants first. The blastocyst implants within the functional layer of the endometrium during the progestational phase of the menstrual cycle. The trophoblast differentiates into the cytotrophoblast and syncytiotrophoblast. Fertilization occurs in the ampulla of the uterine tube with the fusion of the male and female pronuclei to...

Medial Longitudinal Fasciculus

The medial longitudinal fasciculus is a fiber bundle interconnecting centers for horizontal gaze, the vestibular nuclei, and the nerve nuclei of CN III, IV, and VI, which innervate skeletal muscles that move the eyeball. This fiber bundle courses close to the dorsal midline of the brain stem and also contains vestibulospinal fibers, which course through the medulla to the spinal cord. Lesions of the fasciculus produce internudear ophthalmoplegia and disrupt the vestibulo-ocular reflex. In the...

General Features

The basal ganglia initiate and provide gross control over skeletal muscle movements. The major components of the basal ganglia include Striatum, which consists of the caudate nucleus and the putamen External and internal segments of the globus pallidus Together with the cerebral cortex and die VL nucleus of the thalamus, these structures are interconnected to form two parallel but antagonistic circuits known as the direct and indirect basal ganglia pathways (Figures IV-9-1 and IV-9-2). Both...

Liver

The liver is the largest gland of the body. It has multiple and complex functions, including exocrine secretion (via bile ducts into the duodenal lumen) and maintenance of optimal concentrations of various components of blood, which it receives via the portal vein from the digestive tract and spleen. The liver parenchyma is divided into many small lobules shaped like polygonal cylinders (Figure 1-7-4). Each cylinder is composed of plates of cells arranged radially around a central vein. Between...

Io medical

Copyright 2000 Go Id Standard Multimedia, Inc. All rights reserved. Copyright 2000 Go Id Standard Multimedia, Inc. All rights reserved. Mitochondria have two membranes. They are about 0.5 fxm in width and vary in length from 1 to 10 xm (Figure 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. The outer membrane is smooth, continuous, and highly permeable. It contains...

Table of Contents

Chapter I Cell Chapter 2 Nervous Tissue Chapter 3 Muscle Tissue Chapter 4 Lymphoid Organs Chapter 5 Integument Chapter 6 Respiratory System Chapter 7 Gastrointestinal Chapter 8 Renal Urinary Chapter 9 Male Reproductive System 73 Chapter 10 Female Reproductive System 79 Chapter l Gonad Chapter 2 Week 1 Beginning of Development 101 Chapter 3 Week 2 Formation of the Bilaminar Embryo 103 Chapter 4 Embryonic Period (Weeks 3-8) 105

Radial nerve

Loss of extensors at the elbow, wrist, and digits weakened extension at the shoulder weakened supination. Sensory loss on posterior arm, forearm, and hand. Sign is wrist drop. Shoulder dislocation may injure the radial nerve. Also, pressure on the floor of axilla may injure nerve (Saturday night palsy). Loss of extensors at the wrist and digits. Sensory loss on the posterior forearm and hand. Sign is wrist drop. Fracture of the shaft of the humerus could lacerate the radial nerve, and the...

Cell Surface

The basement membrane is a sheetlike structure that underlies virtually all epithelia. It consists of the following Basal lamina composed of type IV collagen, glycoproteins (e.g., laminin), and proteoglycans (e.g., heparan sulfate) (Figure 1-1-9). Reticular lamina composed of delicate reticular fibers. Image copyright 1984 Lippincott Williams & Wilkins. Used with permission. Figure 1-1-11. Freeze-Fracture Replica of a Tight Junction Image copyright 1984 Lippincott Williams & Wilkins. Used...

Trigeminal nuclei

The motor nucleus of CNf V is located in the pons just medial to the main sensory nucleus of the trigeminal and adjacent to the point of exit or entry of the trigeminal nerve fibers. These motor fibers supply the muscles of mastication (masseter, temporalis, and medial and lateral pterygoid Figure rV-5-3). The main sensory nucleus is located just lateral to the motor nucleus. The main sensory nucleus receives tactile and pressure sensations from the face, scalp, oral cavity, nasal cavity, and...

Intercostal veins

Anterior branches of the intercostal veins drain to the internal thoracic and musculophrenic veins. Posterior branches drain to the azygos system of veins. Table EI1-2-1. The Four Stages of Lung Development Table EI1-2-1. The Four Stages of Lung Development Respiration is not possible j Premature fetuses cannot survive Respiration is not possible Premature fetuses rarely survive Type I and type II pneumocytes are present Respiration is possible Premature fetuses born between weeks 25 and 28 can...

Medial Lemniscus

The medial lemniscus (ML) contains the axons from cell bodies found in the dorsal column nuclei (gracilis and cuneatus) in. the caudal medulla and represents the second neuron in the pathway to the thalamus and cortex for discriminative touch, vibration, pressure, and conscious proprioception. The axons in the ML cross the midline of the medulla immediately after emerging from the dorsal column nuclei. Lesions in the ML, in any part of the brain stem, result in a loss of discriminative touch,...

Central Nervous System

Remnants of Rathke pouch form cranio pharyngiomas that compress optic chiasm. Thalamus, pineal gland, neurohypophysis, hypothalamus, and the eye Figure IV-2-1. Third Week DerlvHives of the Brain Vesicles Axonal polyneuropathies produce distal glove and stocking weakness or sensory deficits, and are related to axonal transport failure. Diabetes mellitus patients present with sensory neuropathies. Mesencephalon Metencephalon --Spinal cord Myelencephalon Mesencephalon Metencephalon --Spinal cord...

Nerves blood vessels and lymphatics

Innervation of the skin and musculature of the anterior abdominal wall is via branches of the ventral primary rami of the lower six thoracic spinal nerves (includes the subcostal nerve), plus the iliohypogastric and ilioinguinal branches of the ventral primary rami of L1. The major arterial blood supply to the anterior wall is derived from the superior epigastric branch of the internal thoracic artery as well as the inferior epigastric and the deep circumflex iliac branches of the external...

Bilaminar Embryonic Disk

HCG is a glycoprotein, produced by the syncytiotrophoblast, which stimulates the production of progesterone by the corpus luteum (i.e., maintains corpus luteum function). hCC can be assayed in maternal blood at day 8 or maternal urine at day 10 and te the basis for early pregnancy testing. hCG is detectable throughout pregnancy. Low hCG levels may predict a spontaneous abortion or ectopic pregnancy. High hCG levels may predict a multiple pregnancy, hydatidiform mole, or gestational...

Adult structures derived from the dilatations of the primitive heart

The primitive heart forms five dilatations, the fates of which are shown in Table III-2-2. Table III-2-2. Adult Structures Derived From the Dilatations of the Primitive Heart Table III-2-2. Adult Structures Derived From the Dilatations of the Primitive Heart Smooth part of right ventricle (conus arteriosus) Smooth part of left ventricle (aortic vestibule) Trabeculated part of right ventricle Trabeculated part of left ventricle Trabeculated part of right atrium Trabeculated part of left atrium...

Intervertebral Disks

Each disk has an outer portion, the anulus fibrosus, which is composed of fibrocartilage and fibrous connective tissue, and an inner portion, the nucleus pulposus, which is a semigelati-nous fluid with very few, if any, cells. Herniation of a nucleus pulposus is almost always in a posterolateral direction, passing through a rupture of the anulus fibrosus. The herniated nucleus often conies to lie in the intervertebral foramen where it may compress a spinal nerve. The intervertebral disk is...

Anterolateral spinothalamic tract system

The anterolateral system carries pain, temperature, and crude touch sensations from the extremities and trunk. Pain and temperature fibers have cell bodies in the dorsal root ganglia and enter the spinal cord via A-delta and C or class III and class IV dorsal root fibers (Figure IV-4-9). Their fibers ascend or descend a couple of segments in the dorsolateral tract of Lissauer before entering and synaps-ing in the dorsal hom. The second neuron cell bodies are located in the dorsal horn gray...

Segmental Innervation to Muscles of Upper Limbs

The segmental innervation to the muscles of the upper limbs has a proximal distal gradient, i.e., the more proximal muscles are innervated by the higher segments (C5 and C6) and the more distal muscles are innervated by the lower segments (C8 and Tl). Therefore, the intrinsic shoulder muscles are innervated by C5 and C6, the intrinsic hand muscles are innervated by C8 and Tl, the distal arm and proximal forearm muscles are innervated by C6 and C7, and the more distal forearm muscles are...

Jejunum and Ileum

The jejunum begins at the duodenojejunal junction and comprises two fifths of the remaining small intestine. The beginning of the ileum is not clearly demarcated it consists of the distal three fifths of the small bowel. The jejunoileum is suspended from the posterior body wall by the mesentery proper. Although the root of the mesentery is only 9 inches long, the mobUe part of the small intestine is approximately 22 feet in length. Figure 111-3-16, Distribution of Superior Mesenteric Artery...

Circuitry

The basic cerebellar circuits begin with Purkinje cells that receive excitatory input direcdy from climbing fibers and from parallel fibers of granule cells. i Purkinje cell axons project to and inhibit the deep cerebellar nuclei or the vestibular nuclei in an orderly fashion (Figure IV-6-3). Purkinje cells in the flocculonodular lobe project to the lateral vestibular nucleus. Purkinje cells in the vermis project to the fastigial nuclei. Purkinje cells in the intermediate hemisphere primarily...

Ovarian Follicles and Follicular Development

Follicles (Figure 1-10-1) are located in the cortical stroma and are composed of oocytes surrounded by follicular (granulosa) cells. Approximately 400,000 follicles are present in the newborn ovaries. Only a small percentage of the oocytes (approximately 450) reach maturity in the adult. The remaining follicles eventually degenerate through a process called atresia* Atresia may occur at any stage of follicular development. The primary oocyte surrounded by a single layer of flattened follicular...

Cerebellar Cytoarchitecture

All afferent and efferent projections of the cerebellum traverse the ICP, MCP, or SCP Most afferent input enters the cerebellum in the ICP and MCP most efferent outflow leaves in the SCP (Figure IV-6-2 and Table IV-6-2). Internally, the cerebellum consists of an outer cortex and an inner medulla. The three cell layers of the cortex are the molecular layer, the Purkinje layer, and the granule cell layer. The molecular layer is the outer layer and is made up of basket and stellate cells as well...

Cranium

Cribriform plate fractures may result in dysosmia and rhinorrhea (CSF). Foramen magnum Stylomastoid foramen Jugular foramen Carotid canal Foramen spinosum Foramen ovale Foramen lacerum Figure II 1-6-10. Foramina Base of Skull Figure 111-6-11. Foramina Cranial Fossae Figure 111-6-11. Foramina Cranial Fossae Superior orbital fissure Foramen rotundum Foramen ovale Foramen spinosum Foramen lacerum Internal auditory meatus Jugular foramen Hypoglossal canal. Foramen magnum may be caused by a tumor...

Collecting Tubules

Collecting tubules consist of arched and straight segments made up of cells that range from cuboidal to columnar. In response to vasopressin also known as antidiuretic hormone, or ADH) secreted by the neurohypophysis, collecting tubules become permeable to water and, thus, are important in the kidney's role in water conservation and urine concentration. Figure 1-8-7. Renal Corpuscle and Juxtaglomerular Apparatus Figure 1-8-7. Renal Corpuscle and Juxtaglomerular Apparatus

Macula Densa

Cells of the distal tubule near the afferent arteriole are taller and more slender than elsewhere in the distal tubule. They constitute the macula densa. The macula densa is thought to sense sodium concentration in the tubular fluid. The kidney has three major regions the hilum, cortex, and medulla. The hilum is the point of entrance and exit for the renal vessels and ureter. The upper expanded portion of the ureter is called i the renal pelvis, and divides into two or three major calyces and...

Borders of the Heart

The right border is formed by the right atrium (Figure III-2-I4). The left ventricle and the auricle of the left atrium form the left border. The superior border is formed by the right and left auricles plus the conus arteriosus of the right ventricle. The apex is the tip of the left ventricle. The base is opposite the apex, formed mainly by the surface where the pulmonary veins enter the heart (left atrium) and by part of the right atrium. The anterior wall is formed primarily by the right...

Collateral Nerves

In addition to the five terminal nerves, there are several collateral nerves that arise from the brachial plexus proximal to the terminal nerves (i.e., from the rami, trunks, or cords). These nerves innervate proximal limb muscles (shoulder girdle muscles). Table III-4-2 summarizes the collateral nerves. Table III-4-2. The Collateral Nerves of the Brachial Plexus Table III-4-2. The Collateral Nerves of the Brachial Plexus Middle subscapular (thoracodorsal) nerve

Lymph Node

The lymph node is associated with afferent and efferent lymphatic vessels. It is surrounded by a capsule, has trabeculae, and can be divided into outer cortical, inner cortical (paracortical), and medullary regions (Figure 1-4-2) The outer cortex contains most of the nodules and germinal centers. It is populated by most of the B lymphocytes. The inner cortex is populated by T lymphocytes. The thymus contains trabecule and has a cortical and medullary region. Epithelial reticular cells and...

Brown Squard syndrome

Hemisection of the cord results in a lesion of each of the three main neural systems the principal upper motoneuron pathway of the corticospinal tract, one or both dorsal columns, and the spinothalamic tract. The hallmark of a lesion to these three long tracts is that the patient presents with two ipsilateral signs and one contralateral sign. Lesion of the corticospinal tract results in an ipsilateral spastic paresis below the level of the injury. Lesion to the fasciculus gracilis or cuneatus...

Anterior Triangle

The anterior triangle is bounded by the anterior border of the sternocleidomastoid muscle, the anterior midline, and the body of the mandible (Figure 10-6-1). Subdivisions of the anterior triangle contain the strap muscles, the submandibular gland, the common carotid, internal carotid and external carotid arteries, and parts of cranial nerves X and XII. The strap muscles consist of a series of five pairs of muscles which have attachments to bony or cartilaginous structures adjacent to the...

Periaqueductal gray

The periaqueductal (central) gray is a collection of nuclei surrounding the cerebral aqueduct in the midbrain. Opioid receptors are present on many periaqueductal gray cells, the projections from which descend to modulate pain at the level of the dorsal horn of the spinal cord. The brain stem is divided-into three major subdivisions the medulla oblongata, pons, and midbrain. The brain stem contains many descending and ascending tracts, the reticular formation, and the sensory and motor cranial...

Neuroscience

Prevertebral Ganglia

Reduced levels of alpha-feto protein are seen in mothers of fetuses with Down syndrome. Failure to close results in ancephaly causing polyhydraminos and increased alpha-feto protein Failure to close results in spina bifida alpha-feto protein Figure IV-1-1. Third Week Neurulation Table IV-1-1. Germ Layer Derivatives Table IV-1-1. Germ Layer Derivatives Lens of eye Anterior pituitary Parotid gland Tympanic cavity Auditory tube GI tract Neuroectoderm Neural tube Central nervous system Retina S>...

The Brain Stem

The brain stem is divisible into three continuous parts the midbrain, the pons, and the medulla. The midbrain is most rostral and begins just below the diencephalon. The pons is in the middle and is overlain by the cerebellum. The medulla is caudal to the pons and is continuous with the spinal cord. The brain stem is the home of the origins or sites of termination of fibers in 9 of the 12 cranial nerves (CN). Two cranial nerves, the oculomotor and trochlear (CN III and IV), arise from the...

Venous Drainage of the Brain and the Dural Venous Sinuses Dural venous sinuses

Dural Venous Sinus Anatomy

The dural venous sinuses receive cerebral veins from the brain and drain the venous blood mainly into the internal jugular vein (Figures III-6-12 and III-6-13). The superior sagittal sinus is located in the midsagittal plane along the superior aspect of the falx cerebri. It drains into the confluence of the sinuses. Arachnoid granulations protrude through the walls of the superior sagittal sinus. The arachnoid granulations transmit CSJ from the subarachnoid space into the venous circulation....

Control of Horizontal Gaze

Horizontal Eyer Gaze

Horizontal gaze is controlled by two interconnected gaze centers. One control center is in the frontal lobe, the frontal eye field (Brodmann area 8). This area acts as a center for contralateral horizontal gaze. In the pons is a second gaze center, known as the pontine gaze center or the PPRF, the paramedial pontine reticular formation. This is a center for ipsilateral horizontal gaze. When activated by neurons in the frontal eye field, the pontine gaze center neurons send axons to synapse with...

Dopamine and cholinergic effects

Lateral Ventricle Anterior Horn

In addition to the GABA neurons, two other sources of chemically significant neurons enhance the effects of the direct or indirect pathways. Dopaminergic neurons in the substantia nigra in the midbrain project to the striatum. The effect of dopamine excites or drives the direct pathway, increasing cortical excitation. Dopamine excites the direct pathway through D( receptors and inhibits the indirect pathway through D2 receptors. Cholinergic neurons found within the striatum have the opposite...

Parasympathetic System

Parasympathetic Craniosacral outflow Figure 111-1-9 The vertebral column is composed of a series of cervical, thoracic, lumbar, sacral, and coccygeal vertebrae connected by intervertebral disks and ligaments. The disks consist of an outer core erf fibrocartilage, the annulus fibrosus, and an inner part the nucleus pulposus, which developed from the notochord, Herniation of the nucleus pulposus is usually posterolateral where it can compress a spinal nerve at the intervertebral foramen. The...

Dorsal columnmedial lemniscal system

The dorsal column-medial lemniscal system carries sensory information for discriminative touch, joint position kinesthetic or conscious proprioceptive sense, vibratory, and pressure sensations from the trunk and limbs Figures IV-4-7 and IV-4-8 . The primary afferent neurons in this system have their cell bodies in the dorsal root ganglia, enter the cord via class II or A-beta dorsal root fibers, and then coalesce in the fasciculus gracilis or fasciculus cuneatus in the dorsal funiculus of the...

Temporal Lobe Primary auditory cortex

On its superior and lateral aspect, the temporal lobe contains the primary auditory cortex. Auditory cortex areas 41 and 42 is located on the two transverse gyri of Heschl, which cross the superior temporal lobe deep within the lateral sulcus. Much of the remaining superior temporal gyrus is occupied by area 22 auditory association cortex , which receives a considerable projection from both areas 41 and 42 and projects widely to both parietal and occipital cortices. Patients with unilateral...

Syringomyelia

Syringomyelia is a disease characterized by progressive cavitation of the central canal, usually in the cervical spinal cord but may involve other cord regions or the medulla. Early in the disease, there is a bilateral loss of pain and temperature sensation in the hands and forearms as a result of the destruction of spinothalamic fibers crossing in the anterior white commissure. When the cavitation expands, lower motoneurons in the ventral horns are compressed, resulting in bilateral flaccid...

Collateral Nerves of Lumbosacral Plexus

The collateral nerves of the lumbosacral plexus to the lower limb are summarized in Table III-5-2. Table III-5-2. Collateral Nerves of Lumbosacral Plexus Table III-5-2. Collateral Nerves of Lumbosacral Plexus Gluteus medius, gluteus 1 minimus, tensor fasciae latae Nerve to superior gemellus and obturator internus Superior gemellus, obturator internus Nerve to inferior gemellus and quadratus femoris Inferior gemellus, quadratus femoris SI through S2 posterior divisions and S2 through S3 anterior...

Corticobulbar innervation of Cranial Nerve Nuclei

Corticobulbar fibers serve as the source of upper motoneuron innervation of lower motoneurons in cranial nerve nuclei Figure IV-5-4 , Corticobulbar fibers arise in the motor cortex and influence lower motoneurons in all brain stem nuclei that innervate skeletal muscles. This includes Muscles of mastication CN V ' Muscles of facial expression CN VII Palate, pharynx, and larynx CN X Sternocleidomastoid and trapezius muscles CN XI The corticobulbar innervation of cranial nerve lower motoneurons is...

Descending Hypothalamic Fibers

The descending hypothalamic fibers arise in the hypothalamus and course without crossing through the brain stem to terminate on preganglionic sympathetic neurons in the spinal cord. Lesions of this pathway produce an jpsilateral Horner syndrome. Horner syndrome consists of miosis pupillary constriction , ptosis drooping eyelid , and anhidrosis lack of sweating in the face ipsOateral to the side of the lesion. Descending hypothalamic fibers course with the spinothalamic fibers in the lateral...

Innervation of Parietal Pleura

The intercostal nerves supply the costal and peripheral portions of the diaphragmatic pleura. The phrenic nerve supplies the central portion of the diaphragmatic pleura and the mediastinal pleura. Pulmonary hypoplasia occurs when lung development is stunted. This condition can be associated with congenital diaphragmatic hernia herniation of abdominal contents into the thorax, which compresses the lung or with bilateral renal agenesis this causes oligohydramnios, which increases the pressure on...