USMLE Road Map - Fundamentals Flashcards Preview

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Flashcards in USMLE Road Map - Fundamentals Deck (74):

The ... bones of the axial skeleton include the bones of the skull, vertebral column, ribs, sternum, and the hyoid.

80 bones.


The ... bones of the appendicular skeleton include bones of the upper and lower limbs and the pectoral and pelvic girdles, which link the limbs to the axial skeleton.



Bones are covered on their external surfaces by ..., which is continuous with ... .

Periosteum, deep fascia.


Joints are formed where ...?

2 bones are joined together by nonosseous elements.


2 types of joints:

1. Synarthrodial, or solid, joints, collagenous or fibrocartilaginous connective tissue occupies the space between the bony elements --> Little movement is permitted.
2. Diarthrodial, or synovial, joints, a space with synovial fluid separates the articulating surfaces of the opposed bones --> Freedom of movement is permitted.


Skeletal muscle attaches to bone by way of ...?

1. A tendon.
2. An aponeurosis.
3. A fleshy attachment.


Myasthenia gravis - Which muscles are primarily affected?

Muscles innervated by cranial nerves --> Ocular almost always included.


MG - Patients may have ...?

1. Bilateral ptosis.
2. Horizontal diplopia.
3. Dysphagia.
4. Dysarthria.
5. Weakness in chewing and in the muscles of facial expression.
6. Proximal limb muscles may be affected.
--> Cardiac and smooth muscles are SPARED.


Many patients with MG have ...?

Thymic hyperplasia or a thymoma.


Clinical anatomy of the neuromuscular junction:

1. Guillain-Barre --> Axon peripheral myelin affected --> Limb weakness.
2. Lambert-Eaton --> Antibody to the presynaptic voltage-gated Ca channel --> Muscular weakness that improves with exercise.
3. MG --> Autoantibody binding to the nicotinic ACh receptor.
4. Botox --> Prevents release of ACh by binding to presynaptic membrane.
5. Curare --> ACh receptor prevents binding of ACh and causes paralysis.


Lambert-Eaton - What is primarily affected?

Proximal muscles in limbs are primarily affected --> Muscles innervated by cranial nerves are SPARED.
Repetitive contractions of affected muscles temporarily INCREASE strength.


Neurons have cell bodies that are found in either a ganglion or a nucleus. What is the difference?

A ganglion is a collection of neuron cell bodies situated in the PNS.
A nucleus is a collection of neuron cell bodies inside the brain or spinal cord.


There are only 2 types of ganglia:

Sensory + Autonomic.


Sensory ganglia contain cell bodies of ...?

Either pseudounipolar or bipolar sensory neurons.
--> Both types of neurons have a CENTRAL process that acts like an axon in conducting impulses into the CNS and a PERIPHERAL process that acts like a dendrite in conducting impulses from a sensory receptor toward the cell body.


Sensory ganglia - Are there any synapses?

No synapses in the sensory ganglia.


Autonomic ganglia contain ...?

Motor cell bodies --> They are synaptic sites where an impulse is transmitted from the axon of a preganglionic autonomic neuron to the dendrites or cell body of a postganglionic neuron.


Neurons in ganglia are derived from ...?

Neural crest ectoderm.


Nuclei contain ...?

A wide variety of functionally or anatomically similar neurons.
--> Skeletal motor neurons and preganglionic autonomic neurons, which give rise to axons in nerves, are found in nuclei.


Neurons in nuclei are derived from the ...?

Neural tube.


CNS axons with myelin sheath formed by oligodendrocytes ...?

DO NOT regenerate if cut.


Axonal regeneration may be inhibited by ...?

1. Proliferation of glial cells at the site of the lesion.
2. Inflammation.
3. Lack of factors secreted by oligodendrocytes.


Myelinated axons in the PNS have the capacity to ...?

Regenerate down an endoneurial sheath formed by Schwann cells.


Peripheral regeneration occurs at a rate of about ...?

1-4mm/day, but the axons may grow back to the wrong target or may not regenerate completely.


Large acoustic schwannomas may also ...?

Compress the CN VII and the CN V.


There are ... pairs of spinal nerves:

8 cervical.
12 thoracic.
5 lumbar.
5 sacral.
1 coccygeal.


All branches of spinal nerves contain ...?

BOTH motor and sensory fibers.


Spinal nerves are formed by the ...?

Union of a dorsal root and a ventral root that emerge segmentally from the spinal cord and join approximately at the level of an intervertebral foramen.


Each spinal nerve divides into 2 branches:

A dorsal RAMUS and a ventral RAMUS, each of which carry BOTH motor and sensory fibers.


Dorsal rami innervate:

The skin of the medial 2/3 of the back from the vertex of the skull, corresponding to a coronal plane through the external auditory meatuses, to the coccyx.


Dorsal rami ALSO innervate ...?

1. The deep (intrinsic) muscles of the back that act on the vertebral column.
2. The zygoapophyseal (facet) joints between articularr processes of vertebra.


Few branches of dorsal rami form nerves that have names:

1. Suboccipital nerve - Dorsal ramus of C1.
2. Greater occipital nerve - Dorsal ramus of C2.
3. Cluneal nerves that provide cutaneous innervation to the gluteal region.


Ventral rami - Contain ...?

More motor and sensory fibers than dorsal rami and have a more widespread distribution.


The skeletal system consists of bones of the ... and ... skeleton.

Axial and appendicular skeleton.


Ventral rami innervate:

The skin, muscles, and joints in the ventrolateral aspects of the neck and trunk and in both extremities.


Ventral rami - They intermingle to ...?

Form plexuses of fibers that innervate the extremities and the neck - EXCEPT those from the T2-11 spinal nerves.


Ventral rami communicate with ...?

The sympathetic chain of paravertebral (autonomic) ganglia by white and gray communicating rami.


Virtually ALL ventral rami form ...?

Nerves that have names.


Cutaneous branches of dorsal and ventral rami ...?

Supply a SPECIFIC Dermatome, the area of skin supplied by the branches of a single spinal nerve.
--> EXCEPT for the C1 spinal nerve.


The dermatomes supplied by adjacent spinal nerves may ...?

--> A lesion of a single spinal nerve may not result in a cutaneous sensory loss.


Muscular branches of dorsal and ventral rami supply ...?

A SPECIFIC myotome - The muscle mass supplied by the branches of a single spinal nerve.


Splanchnic branches of VENTRAL rami from the ... and ... spinal nerves carry ANS and sensory fibers to organs in the thorax, abdomen, and pelvis.

T1-L2 and S2-S4.


The 4 CNs that are MIXED (V, VII, IX, X) innervate structures derived from ...?

Pharyngeal arches.


Course of PREganglionic SNS neurons:

Leave the cord and course in the ventral roots and ventral rami of the T1 through L2 spinal nerves.
--> They then exit in white rami communicantes to synapse in a paravertebral ganglion in the sympathetic trunk or pass through the trunk to synapse in a prevertebral sympathetic ganglion.


Postganglionic SNS axons from paravertebral ganglia course in ...?

Gray rami, which rejoin all spinal nerve branches to innervate smooth muscle in the walls of blood vessels and sweat glands in the body wall, in both extremities, and in the neck.


Postganglionic sympathetic axons from the paravertebral ganglia also course in ...?

Cervical and upper thoracic (or cardiopulmonary) splanchnic nerves to innervate smooth muscle and glands in the lungs, cardiac muscle, and the conduction system of the heart.


Prevertebral (or collateral) ganglia are found below the ...?



Prevertebral (or collateral) ganglia - They are situated mainly ...?

Around the origins of branches of the abdominal aorta anterior to the bodies of the vertebrae and include:
1. Celiac.
2. Superior mesenteric.
3. Aorticorenal.
4. Inferior mesenteric.


Preganglionic sympathetic axons reach prevertebral ganglia in ...?

1. Lower thoracic.
2. Lumbar.
3. Abdominopelvic splanchnic nerves.


Lower thoracic splanchnic nerves also synapse with ...?

Chromaffin cells in the adrenal medulla, which is essentially a prevertebral ganglion.


SNS vs PNS - Axons exit from CNS in:

SNS --> Ventral roots, then ventral rami of spinal nerves from T1-L2 - Leave white rami to enter paravertebral trunk.
PNS --> In CNs III, VI, IX, X or in ventral roots and rami of spinal nerves S2, S3, S4.


SNS vs PNS - Names of ganglia:

SNS --> Paravertebral (in sympathetic trunk), or prevertebral (found near origins of abdominopelvic arteries).
PNS --> Terminal, ciliary, pterygopalatine, submandibular, otic.


SNS vs PNS - Distribution of postganglionic axons:

SNS --> They go evreywhere; leave paravertebral ganglia to rejoin all spinal nerves in gray rami; leave prevertebral ganglia to course on abdominopelvic arteries or in visceral plexuses.
PNS --> Restricted to head, neck, and viscera; leave named ganglia to course with branches of CN V; leave terminal ganglia to course in visceral plexuses.


SNS vs PNS - Splanchnic nerves (carry autonomic axons and visceral sensory fibers):

SNS --> Cervical and upper thoracic splanchnic nerves: contain postganglionic sympathetic axons from paravertebral ganglia (middle cervical to T5).
Lower thoracic (greater, lesser, lowest) and lumbar splanchnic nerves --> Contain preganglionic sympathetic axons from T5 to L2 spinal cord segments; synapse in prevertebral ganglia.
PNS --> Pelvic splanchnic nerves; carry preganglionics from S2, S3, S4; synapse in abdominopelvic terminal ganglia.


Postganglionic axons from prevertebral ganglia supply ...?

Glands and smooth muscle in organs in the abdomen and pelvis.


Visceral afferent fibers:

Convey physiologic sensations or visceral pain, course with sympathetic and parasympathetic nerves.


Visceral afferents that convey physiologic sensations OTHER THAN PAIN course with ...?

PNS axons in the vagus or pelvic splanchnic nerves.


Visceral pain fibers usually accompany ...?

SNS nerve fibers back to the CNS and enter at thoracolumbar spinal cord levels T1-L2 and refer pain to these dermatomes.


Referred pain:

Corresponds to sensations originate from thoracic, abdominal, or pelvic organs but is perceived consciously in dermatomes on the surface of the body.


Horner's syndrome may be caused by a lesion in ...?

Either preganglionic or postganglionic sympathetic neurons that innervate SWEAT GLANDS and BLOOD vessels in the face and scalp and 2 smooth muscles in the orbit --> The smooth muscles elevate the upper eyelid and dilate the pupil.


Shy-Drager syndrome results from ...?

Degeneration of preganglionic sympathetic and parasympathetic neurons in the brainstem and spinal cord and degeneration of neurons in most ganglia.
--> The syndrome may be combined with loss of other non-autonomic CNS neurons.


Shy-Drager - Patients may experience ...?

1. Impotence.
2. Urinary retention with incr. urinary frequency at night.
3. Dizziness on standing.
4. Blurred vision.
5. Inability to sweat.


Hirschsprung disease is caused by ...?

EITHER a failure of neural crest cells to migrate into the wall of the descending colon, sigmoid colon, or rectum OR to differentiate into terminal PNS ganglia in these areas.


In irritative lesions, nerve fibers are ...?

Compressed and the firing of the irritated sensory or motor neurons is altered.


Irritative nerve lesions of SENSORY fibers commonly results in ...?

1. Hypesthesia - Reduced sensation.
2. Altered sensation (paresthesia).


Irritative lesions of MOTOR fibers may result in ...?

1. Weakness (paresis) of skeletal muscles.


Examples of portal veins:

1. Hepatic portal system.
2. Hypophyseal portal system.


AV shunts are ...?

Interconnections between small arteries and veins found in many tissues. Shunts bypass capillary beds and have thick smooth muscle walls.


Shunts in the skin ...?

Are important for THERMOREGULATION and are used in an attempt to prevent FROSTBITE.


Shunts in the walls of the intestines ...?

Divert blood into the hepatic portal system when nutrients are NOT being absorbed.


Raynaud's disease:

Is characterized by AV shunts that show hyperactive vasoconstriction, resulting in a cooling of the hands and feet.


Large fatty acids are absorbed from the intestine in lymphatic vessels called ...?



Tissues that lack blood vessels also lack lymphatic vessels and include ...?

1. Epidermis.
2. Cartilage.
3. CNS.
4. Thymus.


Regions of specialized circulation are found in the ...?

1. CNS.
2. The pleural cavity.
3. The pericardial cavity.
4. The peritoneal cavity.
5. The inner ear.
6. The eye.


Aqueous humor:

A fluid similar in composition to CSF, provides nutrients for the lens and the cornea of the eye.
--> Circulation of aqueous humor determines intraocular pressure.