Circulation & Respiration

Function of the circulatory system• In vertebrates, there are 3 functions

– transport• O2, nutrients, waste products, hormones, immune

system cells– thermoregulation

• by expanding or contracting blood vessels closest to the exterior of the body, an animal can absorb or release heat

– protection• immune cells fight pathogens & platelets & certain

chemicals limit blood loss during injury

Circulatory system parts• Muscular pump

– the heart(s)– in vertebrates, composed of

• atrium(a): receive blood from body• ventricle(s): pump blood to body

• Circulatory fluid– blood or hemolymph

• Tubes or vessels to carry blood– arteries, veins, capillaries

Types of circulatory systems• Open circulatory system

– most molluscs & arthropods– hemolymph is pumped

through open-ended vessels & flows out among cells

– no distinction between blood & interstitial fluid

• aqueous solution that surrounds body cells; materials pass back & forth between blood & cells

– hemolymph returns to heart through pores

Types of circulatory systems• Closed circulatory

system– earthworms, squid,

octopus & vertebrates– blood is confined to

vessels which keep it distinct from interstitial fluid

Types of closed circulatory systems

• Fish– single circulation with a 2

chambered heart– atrium receives deoxygenated

blood from body– ventricle pumps blood to gills to

get oxygenated

Types of closed circulatory systems• Amphibians

– double circulation w/ 3 chambered heart

– 2 atria & 1 ventricle; mixing of oxygenated & deoxygenated blood

– can use skin for gas exchange• Reptiles

– similar to amphibians, but ventricle partially divided to reduce mixing; completely divided in crocodilians

Types of closed circulatory systems

• Birds & mammals– double circulation with 4

chambered heart; 2 atria & 2 ventricles

– pulmonary circuit: between heart & lungs

– systemic circuit: between heart & rest of body

– no mixing of oxygenated & deoxygenated blood

• much more efficient

Double circulation continued• right side of heart

pumps to lungs– handles O2 poor blood

• left side of heart pumps to body (much thicker ventricle wall)– handles O2 rich blood

• 2 circuits essential to maintaining the high metabolic rates of birds & mammals

Types of blood vessels• Arteries

– carry blood away from heart to body organs & tissues

– high blood pressure, thicker muscular walls

• Veins– return blood to heart– low blood pressure, thinner walls, valves

to prevent backflow of blood• Capillaries

– convey blood between arteries & veins within each tissue

– only a single RBC think in diameter & very thin walled so materials can diffuse in & out

Comparison of blood vessels

Flow of blood thru human circ sys.

• R ventricle (pulmonary circuit)• pulmonary arteries • lung capillaries• pulmonary veins• L atrium• L ventricle (systemic circuit)• aorta (branches)

– coronary arteries, upper & lower body • capillaries• vena cava (superior or inferior)• R atrium• R ventricle

Blood: a mixture of cells & fluid• Plasma ~ 55%

– the liquid part of blood– 90% water– the rest is salts, ions, proteins, hormones,

vitamins, dissolved CO2, wastes• Hematocrit ~ 45%

– the cellular component of blood– red blood cells: 90% of blood cells

• mostly hemoglobin to carry O2

– white blood cells: 5 kinds• collectively fight infection & cancer

– platelets: cell fragments (little bits of cytoplasm filled with enzymes & chemicals)

• involved in patching damaged blood vessels (clotting)

Blood pressure• The force which blood flows through the arteries• Tells us the magnitude of each heart contraction &

gives clues to cardiovascular health• Two parts to a blood pressure reading

– systolic pressure• the force that blood exerts on the artery walls when the heart

contracts & pumps blood into the arteries• normal range is between 90 – 140 mmHg

– diastolic pressure• the force that blood exerts on the artery wall while the heart is

between beats• normal range is between 60 – 90 mmHg

– because blood isn’t being actively pumped at that moment, the diastolic pressure is always lower than systolic

High & low blood pressure

• High BP (hypertension)– heart muscle must work

harder at all times & arteries can lose some of their elasticity

– influenced by increased viscosity of blood, narrowing of blood vessels, & lengthening of blood vessels

– genetics can play a role– increases risk of

cardiovascular disease

• Low BP (hypotension)– symptom is dizziness,

especially immediately after standing

– can be caused by some medications

– most often not a problem & rarely has long term effects unless caused by an endocrine disorder, malnutrition or internal bleeding

Cardiovascular disease• All diseases of the heart and blood vessels

– heart attack: when cells of the heart are deprived of O2; heart may beat irregularly or not at all

– stroke: blocked arteries or blood clots in the brain lead to cell death in the brain tissues starved of O2

• Ultimately responsible for close to ½ of all deaths in the USA

Cardiovascular disease, con’t• Generally begins with the

development of fatty deposits (plaques) on the inner walls of arteries

• Plaques cause:– atherosclerosis: a narrowing of

the BV (reducing blood flow)– arteriosclerosis: a hardening of

the BV due to Ca deposits (reducing artery elasticity)

• Initial formation of plaques often from circulating cholesterol

“Bad” & “Good” cholesterol• “Bad” cholesterol is LDL (low-density lipoproteins)

– tend to stick to artery walls & initiates the build-up of plaques

• “Good” cholesterol is HDL (high-density lipoproteins)– remains poorly understood– tends to remove cholesterol from arteries & delivers it to

the liver where it can be broken down• Genetic component to cardiovascular disease

– people vary in # of LDL receptors in their liver cells; the more receptors, the easier for person to remove LDL cholesterol from circulation

• Environmental component to cardiovascular disease– poor diet, lack of exercise & smoking can all contribute

Lymphatic system • Three functions that support the circulatory system

– recycling• lymphatic capillaries take in substances & fluids that diffused out of

the blood capillaries and return them to veins in the shoulders

– fight illness• white blood cell-paced lymph nodes remove bacteria, viruses &

cancer cells (thus swelling when fighting infection)

– retrieve nutrients• little projections extend into the small intestine & absorb lipids from

food we eat & shuttles them to the bloodstream

• There is no “lymph pump;” lymph moves when adjacent muscles contract & squeeze fluid onward; lymph vessels have valves (like veins)

Lymphatic system

Malfunctioning lymphatic system• When lymphatic system is

damaged, fluid builds up in the extremities– fluid recovered cannot be

returned to circulatory system

• Damage can be caused by parasite transmitted by mosquito elephantiasis– can be treated with

antibiotics that target symbiotic bacteria

Function of respiratory system• Acquire O2 necessary for

cellular respiration & remove CO2, a waste product of cellular processes

• Two step process– exchange between external

environment & animal’s circulatory system (if there is one)

– exchange between circulatory system and the cells involved in cellular respiration

Diversity in gas exchange systems• Direct diffusion

– gas exchange occurs directly b/w cells & the environment

– in single celled organisms & those with low metabolic demands

• Protruding “skin gills” – balloon-like sacs that increase the

surface area for gas exchange– in sea stars & other echinoderms

• Gills– elaborate extensions of the body that

exchange significant amounts of gasses dissolved in water

– in fish & many marine invertebrates like lobsters & clams

Diversity in gas exchange, cont.• Tracheae

– network of branching tubes connected to tiny openings on the body called spiracles

– in terrestrial insects• Lungs

– internal organs with highly branched, moist surfaces

– in land vertebrates

Structure of human respiratory system • Air enters the nasal cavity where it is warmed and

moistened– air can also enter through the mouth

• Nose & mouth meet at back of throat (pharynx); air moves through voice box (larynx) to the trachea, the tube that takes air into the chest cavity

• The trachea splits, into two tubes, the bronchi, one going to each lung. The bronchi continue to branch into smaller and smaller tubes, the bronchioles

• Eventually, the bronchioles hit a dead end, the alveoli, tiny elastic sacs where air meets the blood vessels & gas exchange takes place– ~300 million alveoli in each lung (!!); lots of surface area

for gas exchange

Human respiratory system

Muscles control air flow in & out of lungs

• Diaphragm: large sheet of muscle on the bottom of the chest cavity

• Intercostals: muscles between the ribs• Both sets of muscles contract increasing the volume

of the chest cavity, causing inhalation; relaxation of muscles causes exhalation

Effects of smoking on respiratory sys.• Smoking introduces 1000s of different chemicals,

many toxic, (including formaldehyde, benzene, ammonia) into the respiratory system resulting in:– damage to the cilia lining the trachea

• reduces the ability to filter out dirt & microbes from the air we breathe

– killing of immune cells that help fight infections further reducing our immune response to pathogens

– trigger mucous secretion that block airways leading to further respiratory difficulties

– after chronic smoking, alveoli become brittle reducing respiratory capacity

– carcinogens in tobacco smoke can lead to cancer• Changes/damage to most body systems. . .

Healthy vs. smoker’s lungs

Connections between respiratory & circulatory systems

• Respiratory facilitates the exchange of gases in the lungs

• Circulatory delivers the O2 that was inhaled to the body tissues and delivers the CO2produced in the body tissues to the lungs for exhalation

• Both play a role in maintaining homeostasis