Post 6 All Heart

Septal Defects

                The heart is slightly larger than a clenched fist and works as a pressure pump and suction.   The right side of the heart receives poorly oxygenated blood from the body via the superior and inferior vena cava and pumps it through the pulmonary trunk and arteries to the lungs for oxygenation.  The left side of the heart receives well oxygenated blood from the lungs through the pulmonary veins and pumps it into the aorta for distribution to the body.  The heart is comprised of four chambers which are the left and right atria and the left and right ventricles.  Atria receive blood and pump it into the ventricles.  The ventricles pump the blood out of the heart to the body.

                Septal defects may occur in the atrium or the ventricles.  Clinically significant atrial septal defects vary widely in size and location and may occur as part of more complex congenital heart disease.  The failure of the closure of the fossa ovalis is an atrial septal defect.  Large atrial septal defects allow oxygenated blood from the lungs to be shunted from the left atrium through the defect into the right atrium, causing enlargement of the right atrium and ventricle and dilation of the pulmonary trunk.  A common site of ventricular septal defects is the intraventricular septum.  The size of the defect varies, and it causes a left to right shunt of blood flow through the defect.  A large shunt increases pulmonary blood flow which causes severe pulmonary disease and may cause cardiac failure.  A ventricular septum defect in the muscular part of the septum is less common and frequently closes spontaneously in childhood.

Valvular Heart Disease

                There are four valves in the heart which aide the pumping of blood.   Valves open and close allowing blood flow in only one direction.  The tricuspid valve is between the right atrium and the right ventricle.  The pulmonary valve is between the right ventricle and the pulmonary artery.  The mitral valve is between the left atrium and left ventricle.  The aortic valve is between the left ventricle and the aorta.  Each valve has cusps that open and close fully under normal conditions.  A defective heart valve does not fully open or close .

                Valvular heart disease produces either stenosis or insufficiency.  Stenosis in valves is the failure of a valve to open fully, slowing blood from the chamber.  Insufficiency is regurgitation, or failure of the valve to close completely, allowing blood to flow back into the chamber it was just ejected from. Disorders involving the valves of the heart disturb the pumping efficiency of the heart and result in an increased workload for the heart.  Turbulence is produced when the high-pressure blood flow is restricted, or when regurgitation occurs.  Murmurs can be heard due to turbulence.  Valvular disease can be acute or chronic.   Damaged or defective cardiac valves can be replaced surgically with artificial or xenografted valves in a valvuloplasty procedure. 

Coronary Artery Disease

                The blood vessels of the heart comprise the coronary arteries and cardiac veins which carry blood to and from most of the myocardium.  The right coronary artery supplies blood to the right atrium, most of the right ventricle, part of the left ventricle, part of the intraventricular septum, the sinoatrial node, and the atrioventricular node via its branches.  The left coronary artery, via its branches, supplies blood to the left atrium, most of the left ventricle, part of the right ventricle, most of the intraventricular septum including the atrioventricular bundle, and the sinoatrial node.

                Coronary artery disease has many different causes, but all result in a reduced blood supply to the myocardial tissue.  A myocardial infarction occurs when area of myocardium has undergone tissue death.   This happens when a major artery that supplies the region of myocardium is blocked by an embolus. An embolus is something that travels in the blood stream and blocks a blood vessel.   The artery no longer supplies blood, and become infarcted and then undergoes necrosis which is tissue death.   The most common sites where this occurs is the anterior intraventricular branch of the left coronary artery, the right coronary artery, and the circumflex branch of the left coronary artery.   Coronary artery disease is one of the leading causes of death.

Sources

Clinically Oriented Anatomy

http://www.americanheart.org/presenter.jhtml?identifier=4598 

http://www.nhlbi.nih.gov/health/dci/images/heart_coronary_artery.gif

Post 5 Breast Cancer, Lung Cancer and Lung Collapse

Breast Cancer

                The breasts are the most prominent superficial structures in the anterior thoracic wall, especially in women.  Both men and women have breasts, but they are normally well developed only in women.  The breast consists of glandular and supporting fibrous tissue embedded within a fatty matrix, together with blood vessels, lymphatics, and nerves.  Mammary glands are present in the breast in the subcutaneous tissue.  They are functionless in men, but are accessory to reproduction in women.  The nipple of the breast is surrounded by the areola.

                Carcinomas of the breast are malignant tumors that usually arise from the mammary gland lobules or ducts.  Over time, cancer cells can metastasize, and invade nearby healthy breast tissue and make their way into the axillary lymph nodes, and on to the venous system.  Breast cancer cells typically spreads by the means of lymphatic vessels.  Breast cancer is always caused by a genetic mutation, but only 5-10% of mutations are genetic, while the other 90% occur as a result to the aging process or normal life processes.  Breast cancer is categorized into five main stages that refer to how far the cells have spread.  In the first stage, Stage 0, cancer cells remain within the breast duct, and have not invaded normal breast tissue.  The stages progress to stage IV, where the cancer has metastasized to other areas of the body. Breast cancers are most common in women, about 1.5% of breast cancers occur in men.  

Lung Cancer

                The lungs are the vital organs of respiration.  Their main function is to exchange oxygen and carbon dioxide with a tidal airflow.  The oxygenated blood is then sent to the heart and distributed to the body.  The pulmonary cavity houses the lungs, and it is completely lined by membranous parietal pleura that reflects onto the lungs at their roots, and becomes the visceral pleura which covers the lungs surface.  Pleural fluid is between to two layers, and it prevents the lungs from collapse and causes the lungs to expand when the thorax expands for inhalation.  Both lungs are pyramidal in shape, but the right lung has three lobes and the left lung has two. Air enters the lungs from the trachea which bifurcates at the level of the thoracic plane into the main bronchi.  The main bronchi branch into lobar bronchi which then branch into segmental bronchi. The segmental bronchi lead to terminal bronchioles and eventually to pulmonary alveolus which is the basic structural unit of gas exchange in the lung.

                Lung cancer is mainly caused by cigarette smoking.  Most cancers arise in the mucosa of the large bronchi and produce a persistent, productive cough.  Malignant tumors metastasize to the bronchompulmonary lymph nodes, and then onto other thoracic lymph nodes.  If the tumor cells reach the blood, common sites of metastasis are the brain, bones, lungs, and suprarenal glands.  It is possible that the tumor cells enter the systemic circulation by invading the wall of a venule in a lung and are transported through the pulmonary veins, left heart, and aorta. Even though tobacco is the primary cause of lung cancer, other risks include radon, asbestos, air pollution, family history, personal history, and age over 65.

Pulmonary collapse

                The lungs are elastic, and recoil to approximately 1/3 of their size when the thoracic cavity is opened.  Normal lungs remain are distended, even when the air passages are open, because the visceral pleura of the lungs adhere to the inner surface of the thoracic walls as a result of the surface tension provided by the pleural fluid.  The pressure in the pleural cavity is sub-atmospheric because of the elastic recoil of the lungs.

Pneumothorax is the entry of air into the pleural cavity and results in lung collapse.  It usually results from penetrating wound of the parietal pleura or from rupture of a pulmonary lesion into the pleural cavity.  Fractured ribs may also tear the visceral pleura and lung producing pneumothorax.  When a lung collapses, it expels most of its air because of its elastic recoil.  Laceration or rupture of the surface of the lung or penetration of the thoracic wall results in hemorrhage and the entrance of air into the pleural cavity.  The amount of blood and air that accumulated determines the extent of the pulmonary collapse.  When a lung collapses, it occupies less volume within the pulmonary cavity, and the pulmonary cavity does not increase in size during inspiration.

Sources:

Clinically Oriented Anatomy

http://www.breastcancer.org/symptoms/understand_bc/what_is_bc.jsp

http://www.cancer.gov/cancertopics/wyntk/lung/page4

http://www.healthcentral.com/common/images/1/19589_6077_5.jpg

Post 4 Dura Mater, Blood Flow in the Brain, & Macula

Dura mater

                The cranial meninges consist of three intracranial layers.  The dura mater is the outermost layer and is intimately applied to the internal surface of the cranial cavity.  The dura mater is comprised of an outer, periosteal, lamina and an inner, meningeal, lamina.  The periosteal lamina is applied to the internal surface of the cranial cavity, and the meningeal lamina is a supporting layer that closely reflects the contours of the brain.  These two layers of the dura mater separate in certain locations to form dural folds that penetrate the large fissures between parts of the brain. The separation creates spaces that accommodate dural venous sinuses, which receive the venous drainage of the brain.  The arachnoid and pia mater are the two layers of the cranial meninges below the dura mater.

                Extradural or epidural hemorrhage occurs when the meningeal arteries leak blood, and that blood collects between the outer, periosteal, layer of the dura mater, and the skull.  This forms an extradural or epidural hematoma.  This is usually caused by a hard blow to the head.  Typically, a brief concussion occurs, followed by a lucid interval of some hours.  Later drowsiness and a coma may occur.  As blood mass increases, compression of the brain occurs.  The dural border or subdural hematoma results in blood mass that splits open the dural cell border creating a space at the dura-arachnoid mater junction.  Dural border hemorrhage is usually venous in origin.

Blood Flow in the Brain

                The brain requires a continuous supply of oxygen and nutrients for function.  The cerebral arterial circle, the circle of Willis, is a pentagon shaped circle of vessels on the ventral surface of the brain.  The arterial circle is form by the anterior communicating artery, anterior cerebral arteries, internal carotid arteries, posterior communicating arteries, and posterior cerebral arteries.  It is an important anastomosis that is located at the base of the brain between the two vertebral and two internal carotid arteries that supply the brain.   Blood is supplied to the circle of willis from the basilar artery which divides into the two posterior cerebral arteries, and the internal carotid arteries.

                A stroke is an interruption of the blood supply to any part of the brain.  Strokes are the most common neurologic disorder affecting adults in the US.  The most common causes of strokes are spontaneous cerebrovascular accidents, such as cerebral thrombosis, cerebral hemorrhage, cerebral embolism, and subarachnoid hemorrhage.  An ischemic stroke is generally caused by an embolism in a major cerebral artery.  Hemorrhagic stroke follows the rupture of an artery or a sac-like dilation on a weak part of an arterial wall.  In time, the weak part of the wall of the aneurysm expands and may rupture, allowing blood to enter the subarachnoid space.

Macula of the Eyeball

                The eyeball contains the optical apparatus of the visual system.  There are three layers to the eyeball, the fibrous layer, vascular layer, and inner layer. The inner layer of the eyeball is the retina.  It is the sensory neural layer of the eyeball.  The macula is a small oval area of the retina with special photoreceptor cones that is specialized for acuity of vision.  At the center of the macula is the fovea centralis, which is the area of the most acute vision.  The macula of the retina is apparent only when the retina is examined with red-free light. 

                Age related macular degeneration is a disease that gradually destroys sharp, central vision.  As the name suggests, it is associated with aging.  The macula is needed for seeing objects clearly and for common daily tasks.  There are two forms of age related macular degeneration, wet and dry.  In wet age related macular degeneration, abnormal blood vessels behind the retina start to grow under the macula, and these new blood vessels often leak blood and fluid which raises the macula from its normal place. Damage to the macula occurs rapidly. Dry age related macular degeneration occurs when the light-sensitive cells in the macula slowly break down, gradually blurring central vision in the affected eye.  Over time, as less of the macula functions, central vision is gradually lost in the affected eye. In some cases, the disease advances slowly and people affected notice little changes in their vision.  In other cases, the disease progress faster and may lead to a loss of vision in both eyes.  Age related macular degeneration is the leading cause of vision loss in American age 60 and older.

Sources:

Clinically Oriented Anatomy

http://www.suite101.com/view_image_articles.cfm/371179

http://www.nei.nih.gov/health/maculardegen/armd_facts.asp#1a

http://www.proprofs.com/flashcards/upload/a1199161.gif

Post 3: Cranium, Scalp, Facial Nerve

Cranium

                The cranium is the skeleton of the head.  The neurocranium is the bony case of the brain, and it  is comprised of eight bones(frontal, ethmoid, sphenoid, occipital, 2 temporal, and 2 parietal).  Most calvarial bones are united by fibrous interlocking sutures.  A suture is the rigid joint that holds the bones together.  The calvaria is the dome-like roof of the neruocranium.    The frontal suture divides the fontal bones, the coronal suture seperates the frontal and parietal bones, the sagittal suture seperates the parietal bones, and the lambdoid suture seperates the parietal and temporal bones.  The bones of the calvaria of a newborn infant are separate by membranous intervals named fontanelles.  They largest occur between the angles of the flat bones.  They include the anterior and posterior fontanelles and the sphenoid and mastoid fontanelles.

                Cranial malformations occur when the cranial sutures close prematurely.  Premature closure of the cranial sutures is called primary craniosynostosis, and it usually does not affect brain development.  The cause is unknown, but genetics appear to play a role.  The malformations are more common in males than in females.  Cranial malformations are often associated with other skeletal anomalies.   Scaphocephaly occurs when the sagittal suture closes prematurely and the anterior fontanelle is small or absent.  Scaphocephaly results In a long, narrow, wedge shaped cranium.  Plagiocephaly occurs when the coronal or lamboid suture closes prematurely, and the cranium is twisted and asymmetrical.  Oxycephaly, or turricephaly, occurs when the coronal suture closes prematurely and the cranium results in a high, tower like shape.  Oxcycephaly is more common in females.

Scalp

                The scalp consists of skin and subcutaneous tissue that cover the nerocranium.  The scalp spans from the superior nuchal lines on the occipital bone to the supra-orbital margins of the frontal bone.  The scalp extends over the temporal fascia to the zygomatic arches.  There are five layers of the scalp.  The first three layers are connected as a unit.  The layers of the scalp, from superficial to deep, are Skin, Connective tissue, Aponeurosis, Loose connective tissue, and Pericranium. 

                There are many definitions and symptoms associated with scalp infections.  There are different types of infections with different underlying causes.   Ringworm is a common scalp infection.  It is a superficial infection of the scalp, and is caused by a mold-like fungi called dermatophytes.  Infection occurs when a particular type of fungus grows and multiplies anywhere on your skin, scalp, or nails.  It is much more common in children.   Symptoms include red, itchy patches on the scalp, bald areas, skin peeling, scaly skin, blisters, rash, and black dots on the scalp.  Ringworm is an aggressive fungus.  The rash is highly contagious and can spread on the body and to others.  Ringworm is normally treated with over the counter products. A few of the other most common scalp conditions are red, burning, and itch scalp, dandruff, dry scalp, scalp dermatitis, eczema, scalp psoriasis, folliculitis, and stress related itching.

Facial Nerve

                The facial nerve, or Cranial Nerve VII,  has both sensory and motor function.  The motor root supplies the muscles of facial expression, including the superficial muscle of the neck, auricular muscles, scalp muscles, and others.  The main trunk of the facial nerve runs anteriorly, and gives rise to five terminal branches, which are the temporal, zygomatic, buccal, marginal mandibular, and cervical.  The names of the branches refer to the regions that they supply.

                Bell’s palsy is a disorder that results in weakness or paralysis of some or all of the facial muscles on an affected side.  Injury to the facial nerve or its branches results in Bell’s palsy.  The affected area sags, and facial expression is distorted, making it appear passive or sad.  There may be different symptoms associated depending on the location and amount of the injury on the facial nerve.  Some symptoms include impaired speech, inability to blow, displacement of the mouth causing food and saliva to drip out, inability to chew on one side resulting in food accumulation, eversion of the lower eyelid, and inadequate lubrication of the eye resulting in vulnerability to ulceration and impaired vision.   The specific cause of Bell’s palsy is unknown.

Sources:

Clinically Oriented Anatomy

http://www.dryitchyscalpremedies.com/articles/scalp-infections-symptoms-causes-natural-options-for-fast-relief-treatment-eliminate-scalp-infections-fast-permanently

http://medicalcenter.osu.edu/patientcare/healthcare_services/nervous_system/palsy/Pages/index.aspx

Ulnar, Radial, Median Nerve

Nerves

1. Ulnar Nerve

The ulnar nerve originates from the medial cord of the brachial plexus.  In the forearm it innervates only one and a half muscles.  The ulnar nerve does not give rise to branches during its passage through the arm.   It becomes superficial in the distal forearm.  In the hand, the ulnar nerve provides muscle innervations to most of the muscles. The “funny bone” is actually the point in the arm where the ulnar nerve, passes posterior to the medial epicondyle of the humerus at the elbow. 

                The ulnar nerve is the largest in the body that is unprotected by bone or muscle.  Ulnar nerve injury is common at the funny bone.  The injury results when the medial part of the elbow hits a hard surface and compresses the ulnar nerve. Severe compression produces pain at the elbow that radiates downward.  Ulnar nerve injury usually produces numbness and tingling of the medial part of the palm and the medial one and a half fingers.  Ulnar nerve injury can result in extensive motor and sensory loss to the hand.

Radial Nerve

                The radial nerve provides motor and sensory function in both the arm and forearm.  It branches from the brachial plexus.  The radial nerve divides into a superficial and deep branch in the forearm.   The radial nerve supplies the posterior upper limb muscles, as well as all 12 muscles in the posterior osteofascial compartment of the forearm.  The posterior cutaneous nerve of the forearm arises from the radial nerve in the posterior compartment of the arm and reaches the forearm independent of the radial nerve.  The superficial branch of the radial nerve is also a cutaneous nerve, but it gives rise to articular branches as well.  The deep branch of the radial nerve, also termed the posterior interosseous nerve, runs in between the superficial and deep extensor muscles of the forearm.

                The radial nerve is usually injured in the arm by a fracture of the humeral shaft.  Injury to the deep branch of the radial nerve may occur when wound of the posterior forearm are deep.  If the deep branch of the radial nerve is severed, the inability to extend the thumb and the joints of other digits could occur.  If the superficial branch of the radial nerve is severed, anesthesia occurs to the distal bases of the first and second metacarpals.

Median Nerve

                The median nerve arises from the brachial plexus.  The median nerve is the main source of innervations of the anterior compartment of the forearm.  The only branches that the median nerve has in the arm are small and travel to the brachial artery.  The median nerve branches more in the fore arm.  The major branch of the forearm is the anterior interosseous nerve.  The median nerve supplies branches to most of the muscles of the superficial and intermediate layers in the forearm.

                The most common site for lesion of the median nerve is where it passes through the carpal tunnel.  The median nerve is the most sensitive structure in the tunnel.  It has two terminal sensory branches that supply the sin of the hand.  The median nerve also has a terminal motor branch that serves the thenar muscles.  Loss of coordination and strength in the thumb may occur.  People with carpal tunnel syndrome are unable to oppose the thumb and have difficulty with every day tasks.

Clinically Oriented Anatomy

http://anatomy.med.umich.edu/musculoskeletal_system/hand_tables.html

http://en.wikipedia.org/wiki/Radial_nerve