HODS - November 20061 Anatomy and Physiology Heart, Lungs, Pancreas, Liver, Kidneys and Skin B. Paul White, MD HOD ID#: 2078

HODS - November 2006 1

Anatomy and PhysiologyHeart, Lungs, Pancreas, Liver, Kidneys and Skin

B. Paul White, MDHOD ID#: 2078



HEART


HEART

• Hollow, muscular organ• 300 grams (size of a fist)• 4 chambers• found in chest between lungs • surrounded by membrane called

Pericardium• Pericardial space is fluid-filled to nourish

and protect the heart.


HEART ANATOMY

• The heart is a complex muscular pump that maintains blood pressure and flow through the lungs and the rest of the body.

• The heart pumps about 100,000 times and moves 7200 liters (1900 gallons) of blood every day.


HEART ANATOMY

The heart has four chambers.

Two atria act as collecting reservoirs.

Two ventricles act as pumps.

The heart has four valves for: Pumping action of the

heart. Maintaining

unidirectional blood flow.


Functions of the Heart

• Generates blood pressure• Routes blood

– Heart separates pulmonary and systemic circulation

• Ensures one-way blood flow– Heart valves ensure one-way flow


Functions of the Heart

• Regulates blood supply– Changes in contraction rate and force

match blood delivery to changing metabolic needs

– Most healthy people can increase cardiac output by 300–500%

• Heart failure is the inability of the heart to provide enough blood flow to maintain normal metabolism


Cardiac Cycle

• The heart is two pumps that work together, right (pulmonary) and left (systemic) half

• Repetitive, sequential contraction (systole) and relaxation (diastole) of heart chambers

• Blood moves through circulatory system from areas of higher to lower pressure.– Contraction of heart produces the pressure


Cardiac Cycle


HEART Deoxygenated blood returns

to the heart via the superior and inferior vena cava, enters the right atrium, passes into the right ventricle, and from here it is ejected to the pulmonary artery.

Oxygenated blood returning from the lungs enters the left atrium via the pulmonary veins, passes into the left ventricle, and is then ejected to the aorta.


Blood Vessels

• Blood vessels are divided into a pulmonary circuit and systemic circuit.

• Artery - vessel that carries blood away from the heart. Usually oxygenated

• Vein - vessel that carries blood towards the heart. Usually deoxygenated.

• Capillary - a small blood vessel that allow diffusion of gases, nutrients and wastes between plasma and interstitial fluid.


Blood Vessels

• Systemic vessels– Transport blood through the body part from

left ventricle and back to right atrium

• Pulmonary vessels– Transport blood from right ventricle through

lungs and back to left atrium• Blood vessels and heart are regulated to

ensure blood pressure is high enough for blood flow to meet metabolic needs of tissues


Blood Flow


LUNGS

• Lungs comprised of – Airways– Alveoli

http://www.aduk.org.uk/gfx/lungs.jpg


What do the lungs do?

• Primary function is gas exchange

• Let oxygen move in

• Let carbon dioxide move out


How do the lungs do this?

• First, air has to move to the region where gas exchange occurs.

• For this, you need a normal ribcage and respiratory muscles that work properly (among other things).


Conducting Airways

• Air travels via laminar flow through the conducting airways comprised of the following: trachea, lobar bronchi, segmental bronchi, subsegmental bronchi, small bronchi, bronchioles, and terminal bronchioles.


How do the lungs do this?

• The airways then branch further to become transitional/respiratory bronchioles.

• The transitional/respiratory zones are made up of respiratory bronchioles, alveolar ducts, and alveoli.


Weibel ER: Morphometry of the Human Lung. Berlin and New York: Springer-Verlag, 1963

The Airways• Conducting zone: no

gas exchange occurs

– Anatomic dead space

• Transitional zone: alveoli appear, but are not great in number

• Respiratory zone: contain the alveolar sacs

• Over 8 million branches


How does gas exchange occur?

• Numerous capillaries are wrapped around alveoli.

• Gas diffuses across this alveolar-capillary barrier.

• This barrier is as thin as 0.3 μm in some places and has a surface area of 50-100 square meters!


Gas Exchange

• Diffusion Barrier crossed by O2 moving from air to blood and CO2 from blood to air is made up of:

• 1. an aqueous surface film

• 2. epithelial cells of alveolus

• 3. interstitial layer

• 4. endothelial cells of capillaries

• 5. blood plasma

• 6. membrane of RBCs


Alveoli

• Approximately 300 million alveoli

• 1/3 mm diameter• Total surface area

about 85 sq. meters (size of a tennis court)


Gas Exchange

From Netter Atlas of Human Anatomy, 1989


Control of Ventilation

• Arterial PO2– When PO2 is VERY low, ventilation increases

• Arterial PCO2– The most important regulator of ventilation, small

increases in PCO2, greatly increases ventilation

• Arterial pH– As hydrogen ions increase, alveolar ventilation

increases, but hydrogen ions cannot diffuse into CSF as well as CO2

PANCREAS


Anatomy of the Pancreas

• 5" long by 1" thick• Head close to curve in C-

shaped duodenum• Main duct joins common

bile duct from liver • Sphincter of Oddi on

major duodenal papilla• Opens 4" below pyloric

sphincter

HODS - November 2006 28Gray’s Anatomy of the Human Body



Gray’s Anatomy of the Human Body Robbins Basic Pathologyhttp://faculty.clintoncc.suny.edu/faculty/Michael.Gregory/default.htm

Digestive gland that secretes digestive enzymes into the duodenum through the pancreatic duct.

Exocrine glands have ducts that carry their secretions to specific locations.


Histology of the Pancreas


Histology of the Pancreas

• Acini- dark clusters – 99% of gland– produce pancreatic

juice

• Islets of Langerhans– 1% of gland– pale staining cells– produce hormones

Bicarbonate Ion Production

Functions of the Pancreas

• Anatomy– Endocrine

• Pancreatic islets produce insulin and glucagon

– Exocrine• Acini produce

digestive enzymes

– Regions: Head, body, tail

• Secretions– Pancreatic juice

(exocrine)• Trypsin• Chymotrypsin• Carboxypeptidase• Pancreatic amylase• Pancreatic lipases• Enzymes that reduce

DNA and ribonucleic acid

Bicarbonate Ion Production

LIVER


LIVER• Largest gland in the body (1.4 kg – 3 lbs.)• Produces bile

– Stored in GB– Emulsifies fats

• Involved in metabolism• Diaphramatic and visceral surface• Right and left lobes• Porta hepatis = major vessels and nerves• Right and left hepatic ducts, common bile,

common


Histology of the Liver

• Hepatocytes arranged in lobules • Sinusoids in between hepatocytes

are blood-filled spaces • Kupffer cells phagocytize

microbes & foreign matter






Functions of the Liver• Bile production

– Salts emulsify fats, contain pigments as bilirubin

• Storage– Glycogen, fat, vitamins, copper and iron

• Nutrient interconversion• Detoxification

– Hepatocytes remove ammonia and convert to urea

• Phagocytosis– Kupffer cells phagocytize worn-out and dying red and white blood cells,

some bacteria

• Synthesis– Albumins, fibrinogen, globulins, heparin, clotting factors


Bile

• About 600 ml of bile is produced daily– Bile acid– Phospholipids– Cholesterol– Bilirubin– Waste products– Electrolytes– Mucin


KIDNEYS


KIDNEYS• Play a major role in maintaining homeostasis• Maintain water balance• Regulate the quantity and concentration of

ECF ions• Regulate the plasma volume• Regulate pH by controlling elimination of acid

and base in urine • Maintain osmolarity• Regulate the concentration of plasma

constituents (e.g. electrolytes and water)


KIDNEYS

• Kidneys have excellent blood supply: 0.5% total body weight but ~20% of Cardiac Output.

• Kidneys process plasma portion of blood by removing substances from it, and in a few cases, by adding substances to it.

• Works with cardiovascular system (and others!) in integrated manner


Functions of the kidneys

• Regulation of H2O and inorganic ion balance – most important function!

• Removal of metabolic waste products from blood and excretion in urine.

• Removal of foreign chemicals in the blood (e.g. drugs) and excretion in urine.

• Gluconeogenesis• Endocrine functions (e.g. renin, erythropoetin, 1,25-

dihydroxyvitamin D) • In kidney disease, build-up of waste serious, but not

a bad as ECF volume and composition disturbances.


Functions of the kidneys

• Water balance

• Electrolyte balance

• Plasma volume

• Acid-base balance

• Osmolarity balance

• Excretion

• Hormone secretion


Acid-Base Balance

• Kidneys VERY important for acid-base balance, along with respiratory system.

• Important because all biochemical processes must occur within an optimal pH window.

• Prevent ACIDOSIS or ALKALOSIS.• Although the lungs excrete a large amount of CO2, a

potential acid formed by metabolism, the kidneys are crucial for excreting non-volatile acids.

• To maintain acid-base balance, kidney must not only reabsorb virtually all filtered HCO3

-, but must also secrete into the urine the daily production of non-volatile acids.


KIDNEY


Internal Anatomy of Kidneys

• Cortex: Outer area– Renal columns

• Medulla: Inner area– Renal pyramids

• Calyces– Major: Converge to form

pelvis– Minor: Papillae extend

• Nephron: Functional unit of kidney– Juxtamedullary– Cortical


Kidney Failure

• at age 49 years, the expected duration of life of a patient with end-stage renal disease on hemodialysis is 7 additional years compared with approximately 30 additional years for a person of the same age from the general population.


Dialysis and Transplant

Peritoneal dialysis

Hemo-dialysis


SKIN


SKIN

• Largest organ of the body.

• Surface area 1.5 - 2 m2.

• Average adult weight 9 kg.

• Functions - protection, defence, sensation, thermoregulation, vit D synthesis, excretion, storage.


SKIN2 Principal portions

• Epidermis - epithelium

• Dermis – areolar & dense irregular connective tissue

• Hypodermis– “beneath the dermis”– the subcutaneous layer

next to:• adipose layer or

• muscle or

• bone


Functions of the Skin• Protection

– Prevents invasion of environmental toxins and microorganisms

• Immunologic – Sebum has antibacterial properties which helps shed topical

bacteria

• Thermoregulation – Insulates from heat loss and controls loss of heat through

evaporation


Functions of the Skin• Fluid and Electrolyte Balance

– Controls sodium excretion– Sebum retards fluid loss from skin

• Metabolism– Produces Vitamin D– Prevents excessive fluid loss

• Neurosensory – Nerve endings and receptors process environmental stimuli for pain,

touch, heat and cold

• Social and Interactive

– Provides body image and personal identity


Epidermis• Provides barrier function.

• Multilayered structure, continually regenerating.

• Thickness dependent on exposure to friction.

• Stratified squamous epithelium, organised in five layers.– Stratum basale; Stratum spinosum, Stratum

granulosum, Stratum lucidum, Stratum corneum.


Epidermis

• First layer of defense• Composed of dead, keratinized

cells and surrounded by a lipid monolayer

• There are no blood vessels. It is fed by capillaries in the dermis.

• If the epidermis is destroyed but the appendages of the dermis remain, a new epidermis is formed when the epithelial grow out of the hair follicles.


• EPIDERMIS• 4 cell types

– Keratinocytes - 90%• filled with keratin (protein)• waterproof barrier

– Melanocytes - 8%• produce melanin (pigment)• pass melanin to

keratinocytes

– Langerhans cells• phagocytes (from immune

system)• easily damaged by UV light

– Merkel cells• in deepest layer of hairless

skin• sensory transduction -

touch


Epidermis

SS

SG

B

SC


Dermis

• Varies in thickness across body.

• 1 mm on face , 4 mm on back.

• Responsible for most major functions of the skin.

• Two distinct layers:

Papillary dermis,

Reticular dermis.


Dermis• Few cells present - fibroblasts,

macrophages, adipocytes

• Intracellular matrix thick with many protein fibers: collagen, elastin, reticular

• The location for blood vessels, nerves and sensory receptors, glands, hair follicles


• Collagen and fibrous connective tissue• Contains capillaries and arterioles• Has special sensory nerve fibers and

lymph system– Meissner Corpuscle: light touch, just

beneath epidermis– Vater Pacini Corpuscles: pressure

sensors, deep in subq– Ruffini Corpuscles: heat sensors, deep

in subq tissue– Krause Corpuscles: cold sensors,

deep in subcutaneous tissue

Dermis


Dermis• Papillary region -

outer layer - 20%– areolar connective

tissue, elastic fibers– dermal papillae –

mound-like projections to increase the surface area for nutrition from capillaries

– some papillae contain Meissner's corpuscles (for light touch)


Dermis• Reticular region-

80%– dense, irregular

connective tissue – collagen, elastic

fibers in a network surrounding the various cells

– fibers give strength, elasticity, extensibility

– tears in reticular region - "stretch marks“ - long straight red or white streaks


Layers of the Dermis.


• Connective tissue• Fat cells in most areas• Blood vessels• Nerves• Base of hair follicles• Function:

• Insulation• Storage of nutrients

Subcutaneous Tissue


Skin Blood Vessels

Superficial dermal plexus.

Cutaneous plexus

Subcutaneous plexus.


Types of Burns

• Superficial

• Superficial partial thickness

• Deep partial thickness

• Full thickness


Partial Thickness Burn

• Can be superficial or deep

• Involves epidermis and dermis

• Has blister formation

• Moist appearance

• Tactile and pain sensors intact

• Will usually heal on own but will scar


Full Thickness Burn

• Involves all layer of skin

• Has waxy and dry appearance

• Elasticity destroyed

• Painless

• Does not heal without intervention – Autologous skin graft or banked skin

Documents

HODS - November 20061 Anatomy and Physiology Heart, Lungs, Pancreas, Liver, Kidneys and Skin B. Paul White, MD HOD ID#: 2078