NEET MDS Synopsis
Other lung diseases
General Pathology
Other lung diseases
1.Sarcoidosis
1. Sarcoidosis
a. More common in African-Americans.
b. Associated with the presence of noncaseating granulomas.
Sarcoidosis is an immune system disorder characterised by non-necrotising granulomas (small inflammatory nodules). Virtually any organ can be affected, however, granulomas most often appear in the lungs or the lymph nodes.
Signs and symptoms
Sarcoidosis is a systemic disease that can affect any organ. Common symptoms are vague, such as fatigue unchanged by sleep, lack of energy, aches and pains, dry eyes, blurry vision, shortness of breath, a dry hacking cough or skin lesions. The cutaneous symptoms are protean, and range from rashes and noduli (small bumps) to erythema nodosum or lupus pernio
Renal, liver, heart or brain involvement may cause further symptoms and altered functioning. Manifestations in the eye include uveitis and retinal inflammation
Sarcoidosis affecting the brain or nerves is known as neurosarcoidosis.
Hypercalcemia (high calcium levels) and its symptoms may be the result of excessive vitamin D production
Sarcoidosis most often manifests as a restrictive disease of the lungs, causing a decrease in lung volume and decreased compliance (the ability to stretch). The vital capacity (full breath in, to full breath out) is decreased, and most of this air can be blown out in the first second. This means the FEV1/FVC ratio is increased from the normal of about 80%, to 90%.
Treatment
Corticosteroids, most commonly prednisone
2. Cystic fibrosis
a. Transmission: caused by a genetic mutation (nucleotide deletion) on chromosome 7, resulting in abnormal chloride channels.
b. The most common hereditary disease in Caucasians.
c. Genetic transmission: autosomal recessive.
d. Affects all exocrine glands. Organs affected include lungs, pancreas, salivary glands, and intestines. Thick secretions or mucous plugs are
seen to obstruct the pulmonary airways and intestinal tracts.
e. Is ultimately fatal.
f. Diagnostic test: sweat test—sweat contains increased amounts of chloride.
3. Atelectasis
a. Characterized by collapse of the alveoli.
b. May be caused by a deficiency of surfactant and/or hypoventilation of alveoli.
Proteins
PhysiologyProteins:
about 50 - 60% of the dry mass of a typical cell
subunit is the amino acid & amino acids are linked by peptide bonds
2 functional categories = structural (proteins part of the structure of a cell like those in the cell membrane) & enzymes
Enzymes are catalysts. Enzymes bind temporarily to one or more of the reactants of the reaction they catalyze. In doing so, they lower the amount of activation energy needed and thus speed up the reaction
Internal Muscles of the Pharynx
AnatomyInternal Muscles of the Pharynx
The internal, chiefly longitudinal muscular layer, consists of 3 muscles: stylopharyngeus, palatopharyngeus, and salpingopharyngeus.
They all elevate the larynx and pharynx during swallowing and speaking.
The Stylopharyngeus Muscle
This is a long, thin, conical muscles that descends inferiorly between the external and internal carotid arteries.
It enters the wall of the pharynx between the superior and middle constrictor muscles.
Origin: styloid process of temporal bone.
Insertion: posterior and superior borders of thyroid cartilage with palatopharyngeus muscle.
Innervation: glossopharyngeal nerve (CN IX).
It elevates the pharynx and larynx and expands the sides of the pharynx, thereby aiding in pulling the pharyngeal wall over a bolus of food.
The Palatopharyngeus Muscle
This is a thin muscle and the overlying mucosa form the palatopharyngeal arch.
The Salpingopharyngeus Muscle
This is a slender muscle that descends in the lateral wall of the pharynx.
The over lying mucous membrane forms the salpingopharyngeal fold.
Origin: cartilaginous part of the auditory tube.
Insertion: blends with palatopharyngeus muscle.
Innervation: through the pharyngeal plexus.
It elevates the pharynx and larynx and opens the pharyngeal orifice of the auditory tube during swallowing.
Blood Transfusions
PhysiologyBlood Transfusions
Some of these units ("whole blood") were transfused directly into patients (e.g., to replace blood lost by trauma or during surgery).
Most were further fractionated into components, including:
RBCs. When refrigerated these can be used for up to 42 days.
platelets. These must be stored at room temperature and thus can be saved for only 5 days.
plasma. This can be frozen and stored for up to a year.
safety of donated blood
A variety of infectious agents can be present in blood.
viruses (e.g., HIV-1, hepatitis B and C, HTLV, West Nile virus
bacteria like the spirochete of syphilis
protozoans like the agents of malaria and babesiosis
prions (e.g., the agent of variant Crueutzfeldt-Jakob disease)
and could be transmitted to recipients. To minimize these risks,
donors are questioned about their possible exposure to these agents;
each unit of blood is tested for a variety of infectious agents.
Most of these tests are performed with enzyme immunoassays (EIA) and detect antibodies against the agents. blood is now also checked for the presence of the RNA of these RNA viruses:
HIV-1
hepatitis C
West Nile virus
by the so-called nucleic acid-amplification test (NAT).
Verruca vulgaris
General Pathology
Verruca vulgaris
1. Commonly known as warts.
2. Caused by the human papillomavirus (HPV).
3. Warts can be seen on skin or as an oral lesion (vermilion border, oral mucosa, or tongue).
4. Transmitted by contact or autoinoculation.
5. A benign lesion.
Antifungal
Pharmacology
Antifungal
There are several classes of antifungal drugs.
The polyenes bind with sterols in the fungal cell wall, principally ergosterol. This causes the cell's contents to leak out and the cell dies. Human (and other animal) cells contain cholesterol rather than ergosterol so are much less suceptible.
Nystatin
Amphotericin B
Natamycin
The imidazole and triazole groups of antifungal drugs inhibit the enzyme cytochrome P450 14α-demethylase. This enzyme converts lanosterol to ergosterol, and is required in fungal cell wall synthesis. These drugs also block steroid synthesis in humans.
Imidazoles:
Miconazole
Ketoconazole
Clotrimazole
The triazoles are newer, and are less toxic and more effective:
Fluconazole
Itraconazole
Allylamines inhibit the enzyme squalene epoxidase, another enzyme required for ergosterol synthesis:
Terbinafine
Echinocandins inhibit the synthesis of glucan in the cell wall, probably via the enzyme 1,3-β glucan synthase:
Caspofungin
Micafungin
Others:
Flucytosine is an antimetabolite.
Griseofulvin binds to polymerized microtubules and inhibits fungal mitosis.
Weak Acids and pKa
Biochemistry
Weak Acids and pKa
• The strength of an acid can be determined by its dissociation constant, Ka.
• Acids that do not dissociate significantly in water are weak acids.
• The dissociation of an acid is expressed by the following reaction: HA = H+ + A- and the dissociation constant Ka = [H+ ][A- ] / [HA]
• When Ka < 1, [HA] > [H+ ][A- ] and HA is not significantly dissociated. Thus, HA is a weak acid when ka < 1.
• The lesser the value of Ka, the weaker the acid.
• Similar to pH, the value of Ka can also be represented as pKa.
• pKa = -log Ka.
• The larger the pKa, the weaker the acid.
• pKa is a constant for each conjugate acid and its conjugate base pair.
• Most biological compounds are weak acids or weak bases.
Tubular secretion
Physiology
Tubular secretion:
Involves transfer of substances from peritubular capillaries into the tubular lumen. It involves transepithelial transport in a direction opposite to that of tubular absorption.
Renal tubules can selectively add some substances that have not been filtered to the substances that already have been filtered via tubular secretion.
Tubular secretion mostly function to eliminate foreign organic ions, hydrogen ions ( as a contribution to acid base balance ), potassium ions ( as a contribution to maintaining optimal plasma K+ level to assure normal proceeding of neural and muscular functions), and urea.
Here we will focus on K+ secretion and will later discuss H+ secretion in acid base balance, while urea secretion will be discussed in water balance.
K+ is filtered in glomerular capillaries and then reabsorbed in proximal convoluted tubules as well as in thick ascending limb of loop of Henley ( Na-2Cl-K symporter)
K+ secretion takes place in collecting tubules (distal nephron) . There are two types of cells in distal nephron:
- Principal cells that reabsorb sodium and secrete K+ .
- Intercalated cells that reabsorb K+ in exchange with H+.
Mechanism of secretion of K+ in principal cells : Two steps
- K+ enters tubular cells by Na/K ATPase on the basolateral membrane.
- K+ leaves the tubular cells via K+ channels in apical membrane.
Aldosterone is a necessary regulatory factor.
If there is increased level of K+ in plasma,excessive K+ is secreted , some of which is reabsorbed back to the plasma in exchange with H+ via the intercalated cells.