Today: May 1, 2006

• Aging of the Urinary tract

• Aging of the Lung

• Aging of the GI tract

Aging of the Urinary Tract

Nephron & Renal Circulation

Table 19-1Major Functions of the Kidney

Water and electrolyte regulationMetabolic products excretionHydrogen ion excretion and maintenance of blood pH

Endocrine functions:Renin-angiotensin secretion (blood pressure)Vitamin D activation (Ca++ metabolism)Erythropoietin secretion (hematopoiesis)

2. Renal Tubules divided into:• Proximal Tubule, mostly reabsorption of water & solutes• Loop of Henle, mostly reabsorption of water & salt • Distal Tubule, mostly water & salt (under influence of aldosterone) reabsorption and acidification of urine• Collecting Duct, water reabsorption under the influence

of ADH (antidiuretic hormone from posterior pituitary)

1. Glomerulus: Tufts of capillaries between afferent and efferent renal arterioles. Filtration is through a fenestrated endothelium separated from the basal membrane by podocytes. Filtrate is the same as plasma but without proteins.

Distal and Collecting Tubules function is regulated by ADH (antidiuretic hormone)

• secreted by neuroendocrine hypothalamus• stored and released from the posterior pituitary

Juxtaglomerular Apparatus: • located between afferent artery and distal tubule• secretes the enzyme renin• renin acts on the liver protein angiotensinogen to form angiotensin I, and angiotensin is transformed into angiotensin II in the lungs• angiotensin II is a very potent hypertensive substance; it also stimulates the release of aldosterone from the adrenal cortex

Regulation of Kidney function:

PosteriorHypophysis

OxytocinVasopressinAntidiuretic Hormone (ADH)

Fig. 1.11 Diagramme des principales hormones hypophysiotropes de l'hypothamalus et des hormones du lobe posterieur de l'hypophyse.

smooth musclesof uterus

mammaryglandrenal

collectingducts

Hypothalamus, Posterior Hypophysis, and their HormonesHypothalamus

Table 19-2 Common Renal Problems in the Elderly

Renal FailureImpaired drug excretion (Think about kidney when giving a drug)

Urinary tract infectionsHypertensionMiscellaneous disorders:

TuberculosisNephritisDiabetes, etc.

Table 19-3 Some Signs of Renal Failure

Generalized edema

Acidosis

Increased circulating non-protein nitrogen (urea)

Increased circulating urinary retention products (e.g. creatinine, uric acid)

Table 19-4 Selected Causes of Acute Renal Failure

PRE-RENAL: (problems BEFORE the kidney)Loss of body fluidsInadequate fluid intakeSurgical shock or myocardial infarction

RENAL: (problems IN the kidney)Drug toxicity (Think about kidney when giving a drug)Immune reactionsInfectious diseasesThrombosis

POST-RENAL: (problems AFTER the kidney)Urinary tract obstruction

Functions of the bladder• Filling with urine from the kidneys• Micturition: emptying of bladder by muscle contraction and opening of sphincters.• Principle muscle: Detrusor muscle (bladder’s body): when it contracts, the bladder empties• Sphincters: Internal (involuntary; smooth muscle) and external (voluntary to some degree; skeletal muscle)

Table 19-10 Neural Control of Micturition

Muscle (Ty pe) Parasympathetic

Nerves (Cholinergic)

Sympathetic Nerves

(Adrenergic) Somatic Nerves

Detrusor (smooth muscle)

Contraction +++

Relaxation +

No effect

Internal sphincter (smooth muscle)

No effect Contraction

++ No effect

External sphincter (striated muscle)

No effect No effect Relaxation

++

For Micturition:1. Internal and external sphincters have to relax

2. Bladder has to contract (detrosor muscle)

Storage:

Table 19-7Physiologic Requirements for Continence

No involuntary bladder contractions

Appropriate bladder sensation

Closed bladder outlet

Low pressure accommodation of urine

Motivation to be continent

Adequate cognitive function

Adequate mobility and dexterity

Normal lower urinary tractfunction

Emptying:

Table 19-7Physiologic Requirements for Continence

Normal bladder contraction

Lack of anatomic obstruction

Coordinated sphincter relaxation & bladder contraction

Absence of environmental/iatrogenic barriers

Figure 19-6: Mnemonic device for causes of acute

urinary incontinence

Table 19-8 Age-Related Changes Contributing to

Incontinence

In FemalesEstrogen deficiency

Weak pelvic floor and bladder outletDecreased urethral muscle tone

Atrophic vaginitis

In MalesIncreased prostatic sizeImpaired urinary flow

Urinary retentionDetrusor muscle instability

Table 19-9 Management of Urinary Incontinence Type Management Stress Exercises

Alpha-adrenergic agonistsEstrogenSurgery

Urge Bladder relaxantsSurgery

Overflow alpha-adrenergic antagonistsCatheterization

Functional Habit trainingScheduled toiletingHygienic devices

•Weakness of pelvic muscles

•Inability to avoid voiding when bladder full

• overdistended, non-contractile blood

• cognitive, emotional problems

Questions

• What are the major parts of the kidney and what control mechanisms act at each part?

• What are the muscles involved in micturition?

• What are the requirements for continence?

• What are some causes of incontinence?

• How might these be treated?

Aging and the Lung

Functions of the Lung: •Regulation of gaseous exchange• Immunologic defenses of the body

-by phagocytizing particles from inspired air & blood

• Metabolic functions -by synthesizing, storing or releasing into blood substances like surfactant and prostaglandins

• Endocrine functions -by transforming

angiotensin I into angiotensin II (vasoconstrictor and stimulus for aldosterone secretion)

Two lungs activate gas exchange

Chest wallRespiratory muscles

Regulation of respiration by CNS centers & nerve tracts

Activate ventilation

Box 18.1Pulmonary Respiratory System: Structure

Lung, “Battered” Organ

Due to:• Air pollution

• Smoking• Air borne infections

• Oxygen toxicity (e.g. with the use of respirators there is increased

free radical production; therefore, simultaneous administration of antioxidants is recommended)

Major Structural Changes in the Alveolar Ducts & Alveoli with Age

Amount of elastic tissue

Amount of fibrous tissue

TABLE 18-2 Changes with Aging in Respiratory Muscles

Muscle strength

fatigue when work of breathing (as during physical exercise)

Atrophy of some respiratory muscles (primarily Type I muscle fibers of slow, red muscles as in long muscles of back, shoulders)

Ratio of glycolytic (anaerobic) to oxidative (aerobic) metabolism

Blood supply to muscle

Table 18-3 Changes with Age*

Thorax

Calcification of bronchial and costalcartilage

resistance to deformation of chestwall

costovertebral stiffness use of diaphragm in ventilation rigidity of chest wall tidal volume anterior-posterior diameter response to exercise hyperapneaWasting of respiratory muscles maximal voluntary ventilation

Morphologic Changes Functional Consequences

*

* Tidal Volume: Amount of in and out air moving out of lungs with quiet inspiration/expiration

Enlarged alveolar ducts surface area for gas exchange supporting duct framework decreased stretchabilityAlveoli shallow, flatter physiologic dead space (40%)Thinning, separation of alveolar membrane lung elastic recoil mucous gland Vital Capacity 15-20% number, thickness of elastic fibers RV/ TLC 35-40% ** tissue extensibility (alveolar wall) ventilatory flow rate

ventilation distribution pulmonary capillary network resistance to flow in small airways fibrosis of pulmonary

capillary intima ventilation

LUNG

Table 18-3 Changes with Age in the Lung

Morphological Changes Functional Significance

**

*

* Dead Space: Air in the air ways** Vital Capacity (VC): Greatest amount of air expired after maximal inspiration

** Reserve Volume (RV)/Total Lung Capacity (TLC)

Table 18-1 Signs of Impaired Pulmonary Respiration with

Aging

Reduced maximum breathing capacityLess efficient emptying of the lungs

Premature airway closureProgressive reduction in blood oxygenation and in PO2

exchanges between blood and alveolar air

Loss of elastic recoil (i.e. springing back of elastic fibers after stretching)

Increased rigidity of internal lung structureWeakening of respiratory muscles

Decreased elasticity of thorax cage and chest wall

Earlier and easier fatigability

Chronic Obstructive Pulmonary Disease (COPD)

Comprised of three distinct pathologies:

• Chronic bronchitis: inflammation of the bronchi and accompanied by hypersecretion of mucus & cough

• Emphysema: characterized by enlargement of air spaces, destruction of lung parenchyma, loss of lung elasticity and closure of small airways

• Chronic asthma: constriction of the bronchi

TABLE 18-4 Major Risk Factors for

Chronic Obstructive Pulmonary Disease (COPD)

Cigarette smokingAir pollution

Genetic factorsBronchial inflammation

Chronic respiratory tract infectionsOld age

Family history of COPDMale sex

TABLE 18-5 Major Signs of Chronic Obstructive Pulmonary Disease

(COPD)

Structural• Diffuse distention & over- aeration of alveoli

• Disruption of interalveolar septa

• Loss of pulmonary elasticity

• Restructuring of alveoli

• Increased lung volume

• Barrel-shaped chest

Pathophysiologic• Disturbed ventilation

• Altered air and blood flow

• Frequently partial obstruction of bronchi

• Wheezing & more work required for breathing

• Resulting hypoxia (low O2 levels) and hypercapnia (high CO2 levels)

• Chronic productive cough with mucus

• Minor respiratory infections

Table 18-6 (con’t.) Therapeutic strategies:

1. Administration of pharmacological agents (bronchodilators, mucus liquefiers, anti-inflammatory agents, protease inhibitors, antibiotics)

2. Administration of O2 to be used cautiously to prevent acidosis

3. Optimizing function by:-physical exercise to strengthen abdominal

muscles and diaphragm to aid in lung ventilation

-meeting social, emotional and vocational needs.-use of respiratory aids in the form or

aerosols, sprays, etc.

Hematological Profile of Some Older Individuals

Hemoglobin

Hematocrit

RBC number

Onset of erythropoiesis after severe bleeding

Erythropoietic responses to erythropoietin administration

Most of these changes are NOT experienced by centenarians

Oxygen delivery to the tissues is NOT solely dependent on the lungs and those changes, but also on changes in the blood!

Reticulocytes are immature red blood cells. If someone is anemic, you can look at their reticulocyte count to figure out if the problem is that they are breaking down too many red blood cells or if the problem is that they can’t make new ones for many reasons (erythropoiesis). If increased reticulocyte count, that means that the body is destroying mature red blood cells, but not having trouble making new ones. If there are very few reticulocytes, it means that the person is anemic because it can’t make new ones (because of nutrient problems or hormone problems.

Questions

• What are the major changes in the lung with aging (think structure and function)

• What else is responsible for oxygen delivery other than the lungs?

• What are some of the changes in the hematologic (blood) system with aging?

Table 20-1 Major Functions of the Gastrointestinal System

Digestion: chemical (enzymes) and mechanical (teeth, muscles) food breakdown into small units that can be absorbed by the intestinal epithelium

Absorption: active or passive transfer of substances from the GI tract to blood & extracellular spaces

Motility: smooth muscle contraction and relaxation regulate digestion & movement of GI content along tract

Secretion: synthesis and release of hormones, enzymes, chemical mediators, mucus, intrinsic factor

Aging and the GI tract

Aging of Teethpgs. 361-362

• Yellowish brown discoloration (from staining by beverages, tobacco, bacteria)

• Recession of pulp from crown• Narrowing of root canal• Roots become brittle and fracture easily• Odontoblasts (secrete dentin) become irregular and

discontinuous• Pulp calcification• Osteoporosis of mandibular and maxillary bones

contributing to tooth loss• Gum recession and infection (peridontitis)

Disturbance of Deglutitionpg. 363

Dysphagia (disturbance of swallowing of food) maybe associated with:

• Increased incidence of non-peristaltic contraction

• Failure lower esophageal sphincter to relax

• Reduced amplitude of peristaltic contractions

Major Functions of the Stomach

• Food reservoir• Digestion of food• Secretion of gastric juice with digestive enzyme, mucus,

hydrochloric acid• Secretion of hormones gastrin, glucagon, somatostatin,

vasoactive intestinal polypeptide (VIP)• Secretion of intrinsic factor

– necessary for Vitamin B12 absorption & maturation of RBCs

Vasoactive Intestinal Polypeptide (VIP)

• Stimulates intestinal secretion of water & electrolytes

• Relaxes intestinal smooth muscle (including sphincters)

• Inhibit gastric acid secretion

• Dilates peripheral blood vessels

Figure 20-2 Changes in Gastric Secretion with Age

Table 20-4 Important Factors for the Maintenance of Optimal Small Intestinal Function

Anatomic integrity

Normal gastrointestinal secretions.

Coordinated gastrointestinal motility,

Normal intestinal transport

Adequate intestinal blood supply

Normal defense mechanisms against toxic injurious agents (bacteria, injury, drugs)

Decreased intestinal absorption with aging

• Changes in villus shape• Increase of collagen• Mitochondrial changes• Prolonged replication time of cells• Decreased villus motility• Inadequate blood supply (atherosclerosis)• Impaired water barrier restricting diffusion and

transport• Permeability changes

Table 20-3 Mechanisms of Decreased Intestinal Calcium Absorption with Aging

intake of Vitamin D (poor nutrition)

Vitamin D conversion in skin (reduced sunlight exposure)

intestinal absorption

Vitamin D metabolism (hepatic) and activation (renal)

cellular calcium binding (decreased receptors)

Major Liver Functions Bile formation

• Carbohydrate storage and metabolism• Regulation of lipid metabolism • Manufacture of plasma protein• Urea formation • Ketone body formation

Metabolism of steroid & polypeptide hormones

Detoxification of many drugs and toxins

Aging of Liverpg. 370

• Atrophy after 60 years and greater after 80 years• Cell size variable• Increased collagen• Alteration in hepatic cell degeneration/

regeneration cycle• Alteration in mitochondrial number• Decrease in endoplasic reticulum and ability to

metabolize drugs

Major Functions of the Bile

• Emulsification of lipids• Activation of enzymes for digestion of lipids• Excretion of cholesterol

• Conjugation of bilirubin to water soluble products

• Neutralization of acid delivered to duodenum from stomach

• Excretion of drugs, heavy metals, environmental toxins

Questions

• What are the major functions of the GI tract?

• What are the major changes in the GI tract with aging? (Try to think of one from different parts of the GI tract)