Question

1. Explain the renin - angiotensin- aldosterone system (RAAS). Be sure to describe the role of each organ, hormone, and enzyme involved, as well as elaborate on why such a system is necessary even though the kidney is able to regulate glomerular filtration rate through vasoconstriction and vasodilation of the afferent and efferent arterioles.

2). This man has a long history of infectious bronchitis. Why would this chronic smoker be especially susceptible to infections of the bronchi?

3). Explain why this man has bloody sputum (hemoptysis).

4). More than 90% of all cancers (any type: skin, breast, esophageal, lung, etc.) arise from epithelial tissue. Why do you suppose this is the case?

5). if there is an increase in systemic blood pressure, the kidneys respond by causing:

Answer 1

Juxtaglomerular cells are specialized smooth muscle cells situated in the wall of afferent arteriole just before it enters the Bowman capsule. These smooth muscle cells are mostly present in tunica media and tunica adventitia of the wall of the afferent arteriole.

FUNCTIONS OF JUXTAGLOMERULAR APPARATUS

Primary function of juxtaglomerular apparatus is the secretion of hormones. It also regulates the glomerular blood flow and glomerular filtration rate.

Juxtaglomerular apparatus secretes two hormones:

1. Renin

2. Prostaglandin.

Renin ---Juxtaglomerular cells secrete renin which along with angiotensins, renin forms the renin-angiotensin system, which is a hormone system that plays an important role in the maintenance of blood pressure .

Secretion of renin is stimulated by four factors:

i.Fall in arterial blood pressure

ii.Reduction in the ECF volume

iii.Increased sympathetic activity

iv.Decreased load of sodium and chloride in macula densa.

Renin-angiotensin system

When renin is released into the blood, it acts on angiotensinogen. By the activity of renin, the angiotensinogen is converted into called angiotensin I. Angiotensin I is converted into angiotensin II, by the activity of angiotensin-converting enzyme (ACE) secreted from lungs. Angiotensin II has a short half-life of about 1 to 2 minutes.

Angiotensin II is the most active form.

Its actions are: -

On blood vessels:

i. Angiotensin II increases arterial blood pressure by directly acting on the blood vessels and causing vasoconstriction. It is a potent constrictor of arterioles.

ii. It increases blood pressure indirectly by increas ing the release of noradrenaline from postganglionic sympathetic fibers.

On adrenal cortex:

It stimulates zona glomerulosa of adrenal cortex to secrete aldosterone. Aldosterone acts on renal tubules and increases retention of sodium, which is also responsible for elevation of blood pressure.

On kidney:

i. Angiotensin II regulates glomerular filtration rate by two ways:

a. It constricts the efferent arteriole, which causes decrease in filtration after an initial increase.

b. It contracts the glomerular mesangial cells leading to decrease in surface area of glomerular capillaries and filtratio.

ii. It increases sodium reabsorption from renal tubules.

Ans 2 --

Cigarette smoking is indisputably the predominant cause of chronic bronchitis.

Cigarette smoking accounts for 85-90% of chronic bronchitis and chronic obstructive pulmonary disease. Smoking impairs ciliary movement, inhibits the function of alveolar macrophages, and leads to hypertrophy and hyperplasia of mucus-secreting glands. Smoking can also increase airway resistance via vagally mediated smooth muscle constriction. all these factors are responsible for infection.

Ans 3 - Vascular engorgement with erosion is another mechanism of hemoptysis. This occurs within the bronchial capillaries in the mucosa of the tracheobronchial tree as a result of bronchitis.

Ans 4- squamous cell carcinoma is more common.

Please post other question separtely.