Answers and Explanations

Fracture of the medial epicondyle of the humerus may compress the ulnar nerve. Fracture of the scaphoid bone produces pain over the anatomic snuffbox but no nerve compression. Fracture of surgical neck of the humerus might affect the axillary nerve. Fracture of the distal end of the radius might affect the radial nerve. Anterior and inferior dislocation of the head of the humerus might affect either the axillary or the radial nerve. 2. Answer B. Loss of the medial two lumbrical...

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...

Pupillary Light Reflex

When light is directed into an eye, it stimulates retinal photoreceptors and results in impulses carried in the optic nerve to the pretectal area. Cells in the pretectal area send axons to the Edinger-Westphal nuclei on both sides. The Edinger-Westphal nucleus is the parasympathetic nucleus of the oculomotor nefve and gives rise to preganglionic parasympathetic fibers that pass in the third cranial nerve to the ciliary ganglion. Because cells in the pretectal area supply both Edinger-Westphal...

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

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

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...

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>...

Medical

Medial View Rights Eyeball

Skeletal Muscles Innervated by Cranial Nerves (continued) Table III-6-4. Skeletal Muscles Innervated by Cranial Nerves (continued) Copyright 2000 Gold Standard Multimedia, Inc. Alt rights reserved. Copyright 2000 Gold Standard Multimedia, Inc. Alt rights reserved. Figure III-6-18. Head and Neck Posteroanterior View of Skull Figure NI-6-19. Head and Neck Lateral Skull Figure 111-6-22. Head and Neck CT, Skull Figure 111-6-22. Head and Neck CT, Skull Medial Optic Lateral Rectus...

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....

Review Questions

Vitelline Duct Adults

Which structure supplied by a branch of the celiac artery is not derived from foregut endoderm 2. An infant presents with an omphalocele at birth. Which of the following applies to this condition (A) It is also seen in patients with aganglionic megacolon. (B) It results from a failure of resorption of the vitelline duct. (C) It results from herniation at the site of regression of the right umbilical vein. (D) It is caused by failure of recanalization of the midgut part of the duodenum. (E) It...

Control of Horizontal Gaze

Gaze Paralysis

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...

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...