Jackson 5 Flashcards by Tyler Brown

. Other renal functions include:

Gluconeogenesis

Production of hormones

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Kidney produces

erythropoietin – acts in the bone marrow to stimulate synthesis of new erythrocytes

renin – part of renin-angiotensin-aldosterone cascade to regulate blood pressure

1,25-dihydroxyvitamin D – regulate calcium absorption

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renin –

part of renin-angiotensin-aldosterone cascade to regulate blood pressure

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1,25-dihydroxyvitamin D –

regulate calcium absorption

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The actual proportion of the total body water that the kidney “sees” and process is

very small. However, changes in the one, small compartment affected by kidney function can ultimately affect the other compartments.

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ESRD patients have a reduced ability to

eliminate nitrogenous wastes (urea) and excess nitrogen is converted to ammonium.

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ESRD patients;

The excess ammonium has

direct effects on health – the blood is alkalized which leads to an increased pH in the oral cavity.

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Manifestations of renal disease on oral health include:

ammonia breath –

gingival enlargement –

xerostomia –

tooth problems
-premature loss

narrowing pulp chambers
necrosis beneath fillings or crowns

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Contraindications for ESRD patients:

nephrotoxic drugs such as tetracycline, acyclovir, aspirin, NSAIDs

increased susceptibility to bleeding due to destruction of platelets

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in the renal medulla – there are

portions of nephron tubule involved with concentration and collection of urine

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Each kidney contains

~1.2 x 106 nephrons.

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A nephron includes a cluster of

capillaries and a long, hollow tube with a wall that is one cell layer thick.

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Parts of a nephron

renal corpuscle = glomerulus + capsule

proximal (convoluted) tubule

loop of Henle

distal (convoluted) tubule

collecting duct – shared by several nephrons

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The position of a nephron with respect to the

cortical and medullary regions of the kidney can vary somewhat. There are two types of nephrons that differ in the position of the renal corpuscle and the length of the medullary tubules
superficial or cortical nephrons -

juxtamedullary nephrons -

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Regulating blood composition involves three renal processes

Filtration
Secretion
Reabsorption

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filtration – solutes (and the water they are dissolved in) pass from the

blood into the tubular fluid in the renal capsule (Bowman’s space)

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filtration occurs in the

glomerular capillaries; 15-20% of plasma entering glomerulus is filtered

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blood leaving the glomerular capillaries then flows into

peritubular capillaries (vasa recta)

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secretion – substances are transported from the blood in the

peritubular capillaries into the tubular fluid

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reabsorption – substances are transported from the tubular fluid into the blood in the

peritubular capillaries

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Re: renal corpuscle =

glomerulus + renal capsule

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A glomerulus is a dense capillary bed where filtration occurs
surrounded by

renal capsule (or Bowman’s capsule) which collects the filtrate from the blood entering via the afferent arterioles

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filtered blood leaves via

efferent arterioles and flows into peritubular capillaries

Blood flow through the glomerulus is regulated by several mechanisms

smooth muscle contraction in afferent or efferent arterioles

response of the juxtaglomerular apparatus (JGA) located at the intersection of the macula densa of distal tubule with afferent and efferent arterioles –

sympathetic nervous system –

juxtaglomerular apparatus (JGA) secretes the hormone

renin which regulates systemic blood pressure, and, therefore, glomerular blood flow

Proximal convoluted tubule The proximal tubule drains the renal capsule reabsorbs

2/3 of flitered salt and water reabsorbs all filtered glucose and amino acids some diurectics will act here

Loop of Henle | Loop of Henle can be divided into three limbs or segments

thin descending limb thin ascending limb thick ascending limb (TAL)

The loop is the site of

countercurrent multiplication needed to produce concentrated urine, but the loop itself produces a dilute filtrate.

Very powerful diuretics work in the

Loop of Henle.

Distal convoluted tubule | The distal tubule drains the

loop of Henle continued reabsorption of solutes – regulation of calcium – site of action for some diuretics

Collecting duct | Collecting duct – collects fluid from

multiple nephrons

Collecting duct | extends from

cortex through the medulla

Collecting duct | regulates

sodium, potassium, and water some diuretics act here

Renal clearance is the

rate of excretion of a solute through the kidney, expressed as amount per unit time. =

renal clearance represents the

volume of plasma from which all of a particular substance is removed to the urine (i.e. cleared), e.g. 100 ml/min clinically important concept for monitoring renal function

Glomerular filtration rate is the amount of blood filtered by the

kidney, expessed as volume per unit time.

Renal clearance can be used to measure glomerular filtration rate (GFR) based on three criteria

1. the substance must be freely filtered in the glomerulus 2. the substance is not secreted 3. the substance is not reabsorbed

in a normal kidney, GFR (from all nephrons) is

125 ml/min or 180 L/day in females; 90-140 ml/min in males

Inulin and creatinine are substances that can be used to measure

renal clearance

inulin –

small polysaccharide; freely filtered and not secreted or absorbed

creatinine –

product of muscle metabolism; freely filtered, not reasbsorbed, almost no secretion; normal creatinine levels < 1+ 0.5 mg/dl; if > 10 → requires dialysis

Glomerular capillaries are

fenestrated;

podocytes (cells) around the

capillaries form filtration slits

filtrate is

acellular and essentially protein-free

------------------------- are freely filtered

glucose, salts, and amino acids

size is a factor:

< 20 Ǻ freely filtered, > 42 Ǻ not filtered

charge is also a factor

basal lamina (basement membrane) is negatively charged so filtration of moderately-sized, negatively-charged solutes is limited

Filtration occurs due to

pressure differences between the blood in the capillaries and the fluid in the capsule (Starling forces).

Pressure comes from two sources:

hydrostatic pressure = pressure due to fluid P in capillaries > P in capsule fluid ``` oncotic pressure (π) – pressure due to solutes in fluid (including those not dissolved) π in capillaries > π in capsule fluid ```

Net filtration pressure favors filtration from

blood into the capsule fluid GFR ∞ (PGC – PBS) – (πGC – πBS) note that πBS = 0

GFR is affected by

blood flow into and out of the glomerulus, and P gradient is critical to maintain filtration

Despite changes in systemic blood pressure, renal blood flow (RBF) remains

fairly constant | because RBF remains constant, GFR remains constant

Autoregulation involves intrinsic mechanisms that adjust bloodflow through the glomerulus; it is achieved by two primary mechanisms:

1. myogenic mechanism – vascular smooth muscle tends to contract when it is stretched, and relax when not stretched constriction or dilation of smooth muscle in afferent or efferent arterioles has contrasting effects on RBF 2. tubuloglomerular feedback – feedback from the JGA adjusts afferent arteriole diameter and, thus, GFR ↑ GFR à ↑ NaCl in tubular fluid à ↑ NaCl at macula densa à ↑ resistance in afferent arterioles à ↓ GFR

myogenic mechanism –

vascular smooth muscle tends to contract when it is stretched, and relax when not stretched

2. tubuloglomerular feedback –

feedback from the JGA adjusts afferent arteriole diameter and, thus, GFR

Also have extrinsic factors regulating RBF and GFR; some will be discussed in further detail in subsequent lectures

diet – dehydration or hemorrhage – sympathetic nervous system – angiotensin II, aldosterone, and natriuretic peptide -