Circulation in plants and animals

• In cnidarians and flatworms, the gastrovascular cavity functions in both

– digestion

– internal transport

Several types of internal transport have evolved in animals

MECHANISMS OF INTERNAL TRANSPORT

Figure 23.2A

Mouth

Circularcanal

Simple organismsWhen your body is only 2-cell layers thick, you can get

supplies in and waste out just through diffusion

– all cells within easy reach of fluid

HydraJellyfish

Circulatory systems

• All animals have:– muscular pump = heart

– tubes = blood vessels

– circulatory fluid = “blood”

open closed

hemolymph blood

• Most animals have a separate circulatory system, either open or closed

• Open systems

–A heart pumps blood through open-ended vessels into spaces between cells

Figure 23.2B

Pores

Tubular heart

• Closed systems

–A heart pumps blood through arteries and capillary beds

–The blood returns to the heart via veins

Artery(O2-rich blood)

Arteriole

Capillary beds

Venule

Vein

Atrium

VentricleHeart

Artery(O2-poor blood)

Gillcapillaries

Two-chambered heart

• The simplest vertebrate heart is the two-chambered heart, seen in fishes.

• A single atrium receives blood from the body cells. A ventricle sends blood to the gills to collect oxygen.

Three-chambered heart

• Separate atria allow some separation of oxygenated and deoxygenated blood, which was an advantage for land organisms (reptiles, amphibians).

• Though blood can mix in the ventricle, mixing is minimal. Some reptiles have partial separation of the ventricle.

Four-chambered heart

• The four-chambered heart, seen in birds and mammals, allows complete separation of oxygenated and deoxygenated blood.

• Complete separation is necessary to support a fast metabolism found in homeotherms.

Evolution of circulatory system

fish amphibian reptiles birds & mammals

A A

V

V V VV

A AAAA

V

2 chamber 3 chamber 3 chamber 4 chamber

Not everyone has a 4-chambered heart

• The cardiovascular system of land vertebrates has two circuits

• The pulmonary circuit

– conveys blood between the heart and gas-exchange tissues

• The systemic circuit

– carries blood between the heart and the rest of the body

PULMONARYCIRCUIT

A

Systemic capillaries

Lung capillaries

V

Right

SYSTEMICCIRCUIT

A

V

Left

Blood clots plug leaks when blood vessels are injured

Figure 23.16B

• When a blood vessel is damaged, platelets respond

– They help trigger the formation of an insoluble fibrin clot that plugs the leak

Figure 23.16A

Platelet releases chemicalsthat make nearby platelets sticky

Injury to lining of blood

vessel exposes connective

tissue; platelets adhere

1 2 3Platelet plug forms Fibrin clot traps

blood cells

Connectivetissue

Plateletplug

Clotting factors from:

Platelets

Damaged cells

Calcium andother factorsin blood plasma

Prothrombin Thrombin

Fibrinogen Fibrin

Connection: Stem cells offer a potential cure for leukemia and other blood cell diseases

Figure 23.17

• All blood cells develop from stem cells in bone marrow

– Such cells may prove valuable for treating certain blood disorders

BLOOD GROUP SYSTEM

The Rh Factor

Rh-Positive Rh-Negative

Contains the Rh antigen No Rh antigen

Will make antibodies if given Rh-positive blood

Agglutination can occur if given Rh +ve blood

Clinically, it is very important for a female to know her Rh type if she becomes pregnant.

Circulatory SystemBlood Vessels

Blood vesselsarteries

arterioles

capillaries

venules

veins

artery

arteriolesvenules

veins

Arteries: Built for their job• Arteries

– blood flows away from heart

– thicker walls

• provide strength for high pressure pumping of blood

– elastic & stretchable

• maintains blood pressure even when heart relaxes

Major arteries

pulmonaryartery

pulmonaryartery =to lungs

aorta carotid = to headto brain & left arm to right arm

coronary arteries

to body

Coronary artery bypass

bypass surgery

Veins: Built for their job• Veins

– blood returns back to heart– thinner-walled

• blood travels back to heart at low speed & pressure

• why low pressure?– far from heart

• blood flows because muscles contract when we move – squeeze blood through veins

– valves in large veins• in larger veins one-way valves

allow blood to flow only toward heart• Presence of deoxygenated blood imparts bluish black

color to veins

Open valve

Blood flowstoward heart

Closed valve

Major Veins

pulmonaryvein =

from lung

superiorvena cava = from upper body

pulmonaryvein = from lung

inferiorvena cava = from lower body

Structure-function relationship

• Capillaries

– very thin walls

– allows diffusion of materials across capillary

• O2, CO2, H2O, food, waste

• Very slow movement

• Artery—arterioles—capillaries--veins--venules

body cell

O2

food

waste

CO2

Location of Heart in Thorax

Layers of Heart

• Epicardium (most superficial)

– Visceral pleura

• Myocardium (middle layer)– Cardiac muscle

– Contracts

• Endocardium (inner)– Endothelium on CT

– Lines the heart

– Creates the valves

Pulmonaryartery

Superiorvena cava

RIGHTATRIUM

Pulmonaryveins

Semilunarvalve

Atrioventricularvalve

Inferiorvena cava

Aorta

Pulmonaryartery

LEFTATRIUM

Pulmonaryveins

Semilunarvalve

Atrioventricularvalve

RIGHTVENTRICLE

LEFTVENTRICLE

RIGHT VENTRICLE

1

23

Capillaries

of right lung

3

Capillaries

of left lung

4

LEFT ATRIUM5

LEFT VENTRICLE

6

Aorta

7Capillaries of

Head and arms

8

Capillaries of

abdominal organs

and legs

9

Superior

vena cava

10

Inferior

vena cava

11

RIGHT ATRIUM

Pulmonary

vein

Aorta

Pulmonary

vein

Pulmonary

artery

Pulmonary

artery

• Diastole

– Blood flows from the veins into the heart chambers

The heart contracts and relaxes rhythmically

Figure 23.6

Heart is

relaxed.

AV valves

are open.

1 2

3

Atria

contract.

Ventricles

contract.

Semilunar

valves

are open.

SYSTOLE

DIASTOLE

0.4 sec

0.1 sec

0.3 sec

• Systole

–The atria briefly contract and fill the ventricles with blood

–Then the ventricles contract and propel blood out

Mammalian Conducting Pathways

SA node initiates the action potential

◦Depolarization spreads rapidly via internodalpathway through the walls of the atria.

• Depolarization reaches atrioventricular (AV) node which communicates signal to the ventricle.

• AV node causes signal delay

◦allows atrium to finish contracting before ventricles contract.

Cardiac Output

Cardiac Output (CO) = the amount of blood that the heart pumps per unit time.

• CO = HR x SV

• Heart rate (HR) =(72) beats per minute

• Stroke volume (SV) = (80cm3)amount of blood pumped per beat

• 2 part system

– Circulation to lungs

• blood gets O2 from lungs

• drops off CO2 to lungs

• brings O2-rich blood from lungs to heart

– Circulation to body

• pumps O2-rich blood to body

• picks up nutrients from digestive system

• collects CO2 & cell wastes

Circulation of Blood

heart

lungs

body

Circulationto lungs

Circulationto body

Cardiovascular Blood Flow• HeartArteries(conducting-distributing) ArteriolesCapillaries of tissues

• At Capillaries O2 is delivered and CO2 picked up

• CapillariesVenulesVeinsHeart

• Portal System: Special vascular circulation where blood goes through 2 capillary beds before returning to the heart to achieve other function. Begins and end in capillaries.

– (eg) Hepatic Portal System: aids digestion by picking up digestive nutrients from stomach + intestines and delivers to liver for processing/storage

– Pick-up occurs at capillaries of stomach and intestine

– Via Hepatic Portal Vein goes to capillaries of liver

– Via Hepatic Vein blood goes back to heart

Hepatic Portal System

Tissue Fluid

Tissue Fluid

• What is the role of tissue fluid?

It is the fluid which allows the exchange of substances between the blood and cells

• What substances are found in tissue fluid?

glucose, amino acids, fatty acids, salts and oxygen = all delivered to the cells.

carbon dioxide and other waste substances = removed from the cells.

Return of tissue fluid

• Most tissue fluid is returned to the blood plasma via the capillaries. – Hydrostatic pressure at the venule end of the

capillary is higher outside the capillary and tissue fluid is forced back in.

– Osmotic forces (resulting from the proteins in the plasma) pull water back into capillaries.

• Remaining tissue fluid enters the lymph vessels – drain back into the veins close to the heart.

Lymph

• Lymph is moved by:

– Light yellow viscous fluid formed from tissue fluid by special lymph capillaries for passage into venous blood.

– No venous blood, no platelets, lymphocytes and WBC present.

– Contraction of body muscles (aided by valves in the lymph vessels)

42

Lymphatic System

• One way system: to the heart

• Return of collected excess tissue fluid

• Return of leaked protein

• “Lymph” is this fluid

• Edema results if system blocked or surgically removed

Lymph System

44

Lymphoid Organs

• Lymph nodes

• Spleen

• Thymus

• Tonsils

• Small intestine & appendix aggregated lymphoid nodules

45

• Lymph capillaries

– Have one way minivalves allowing excess fluid to enter but not leave

– Picks up bacteria and viruses as well as proteins, electrolytes and fluid

(lymph nodes destroy most pathogens)

46

47

• Lymph capillaries

– Absent from bone, bone marrow, teeth, CNS

– Enter lymphatic collecting vessels

• Lymphatic collecting vessels

– Similar to blood vessels (3 layers), but thin & delicate

– Superficial ones in skin travel with superficial veins

– Deep ones of trunk and digestive viscera travel with deep arteries

– Very low pressure

– Distinctive appearance on lymphangiography

– Drain into lymph nodes

48

• Lymph nodes: bean shaped organs along lymphatic collecting vessels

• Up to 1 inch in size

• Clusters of both deep and superficial LNs

Congenital Heart Disease

• One of most common congenital abnormalities

– 8 in 1000 live births

• Cause usually unknown

• Defects develop in 1st 10 weeks

• Malrotation defects

• Expansion defects

• Septal defects

Malformations with Obstruction to Flow

• Embryonic vessels fail to expand properly

• Coarctation of the aorta

– high BP in arms but low BP in legs

– low blood flow to kidneys

– 50% of cases also have PDA

Pericardial Disease

• Pericarditis

– usually viral infection

– atypical chest pain

– friction rub

• Pericardial effusion

– may occur in noninflammatory conditions

– hemopericardium

Complex Permanent Tissue

A. XYLEM or WOOD

Vascular Tissues -:

Specialized for long-distance transport of water and dissolved

substances.

Contain transfer ceIIs, fibers in addition to parenchyma and

conducting ceIIs

Location- the veins in Ieaves

GW xyIos w/c means “wood”

transports water and dissolved nutrients from the roots to aII parts of a plant.

direction of transport is upward.

Tracheids

Vessels

Xylem fibres or collenchyma

Xylem parenchyma

Living

Dead

• Tracheids

– Characteristics

tapered elongated cells

dead at functional maturity

connect to each other through pits

secondary cell walls strengthened with lignin

– Functions

transport of water & dissolved minerals(?) from cell to cell via pits.

Support

• Vessel Elements– Characteristics

Long tube like and wider than tracheidspossess thinner cell walls than tracheidsAligned end-to-end to form long water-pipesdead at functional maturity

– Functions transport of water plus dissolved mineralssupport

• Xylem fibre: Dead, lignified sclerenchymatous cells supportive in funtion.

• Xylem Parenchyma: Living parenchymatous cells – helps in storage of food

Lateral conduction of sap.

B. PhIoem Greek word phloios meaning, “bark”

transports dissolved organic / food materials from the Ieaves to the different parts of the plant

glucose in phloem moves in aII directions

• Sieve tubes

• Companion cells

• Phloem parenchyma

• Phloem fibres

Living

Dead

• Sieve-tube Members– Characteristics

living cells arranged end-to-end to form food-conducting cells ofthe phloem

lack lignin in their cell walls, perforated walls made sieve plate

mature cells lack nuclei and other cellular organelles

alive at functional maturity

– Functions

transport products of photosynthesis

• Companion Cells– Characteristics

• living cells adjacent to sieve-tube members

• connected to sieve-tube members via plasmodesmata

– Functions

• support sieve-tube members

• may assist in sugar loading into sieve-tube members

Transport in plants

• Water and mineral nutrients must be absorbed by the roots and transported throughout the plant

• Sugars must be transported from site of production, throughout the plant, and stored

Osmotic potential, solutes, and water movement

Low ΨpHigh Ψp

low ψ

Transpiration

creates tension

higher ψ

cohesion

higher ψ

lower ψhigher ψ

lower ψ higher ψ highest ψ

lower ψ

Cells flaccid/Stoma closedCells turgid/Stoma open

Radially oriented cellulose microfibrils

Cellwall

Vacuole

Guard cell

Changes in guard cell shape and stomatal opening and closing (surface view). Guard cells of a typical angiosperm are illustrated in their turgid (stoma open)and flaccid (stoma closed) states. The pair of guard cells buckle outward when turgid. Cellulose microfibrilsin the walls resist stretching and compression in the direction parallel to the microfibrils. Thus, the radial orientation of the microfibrils causes the cells to increasein length more than width when turgor increases. The two guard cells are attached at their tips, so the increase in length causes buckling.

(a)

H2O

H2O

H2OH2O

H2O

K+

Role of potassium in stomatal opening and closing.The transport of K+ (potassium ions, symbolized here as red dots) across the plasma membrane andvacuolar membrane causes the turgor changes of guard cells.

(b)H2O H2O

H2O

H2O

H2O

How do plants regulate the transport of xylem sap?

Stomata

K+ is actively transported into and out of guard cells


Stomata

When [K+] is high, the amount of H20 is high, and guard cells open stomata


Stomata

When [K+] is low, the amount of H20 is low, and guard cells close stomata


Stomata

Light stimulates the uptake of K+ by guard cells, opening stomata


Stomata

Low [CO2] stimulates the uptake of K+ by guard cells, opening stomata


Stomata

Low H2O availability inhibits the uptake of K+ by guard cells, closing stomata

Adhesion and Cohesion Theory

• Cohesion: polar water molecules tend to stick together with hydrogen bonds.

• Adhesion: water molecules tend to stick to polar surfaces.

• Cohesion and adhesion cause water to “crawl” up narrow tubes. The narrower the tube the higher the same mass of water can climb.

• Maximum height: 32 feet.

How do roots absorb water and minerals?

• Roots absorb water and minerals in a 4-step process:

– Active transport of minerals into root hairs.

– Diffusion to the pericycle.

– Active transport into the vascular cylinder.

– Diffusion into the xylem.


Symplastic route: Active transport occurs through proton pumps, that set up membrane potentials, that drive the uptake of mineral ions


Apoplastic route: Some water and dissolved minerals passively diffuse into cell walls


Solutes diffuse through the cells (or cell walls) of the epidermis and cortex (the

innermost layer of which is the endodermis)


The final layer of live cells actively transports solutes into their cell walls

Solutes then diffuse into xylem vessels to be transported upward


The final layer of live cells actively transports solutes into their cell walls

The final layer may be an endodermal cell…


The final layer of live cells actively transports solutes into their cell walls.

… or a cell of the pericycle(outermost layer of stele)

Water transport

How does phloem transport phloem sap?

Companion cells actively transport sugars into sieve-tube members (elements)


Food (sugars) are then translocated from sources to sinks according to the Pressure-Flow Theory:

1. At sources, sugars are actively transported into phloem



2. Water follows by osmosis from source cells and xylem;

this creates high pressure



3. At the sink, sugars diffuse out of the phloem and water follows by osmosis;

this creates low pressure



Sugar solution flows from high to low pressure



4. Water may be taken up by the transpiration stream in the xylem

How does phloem transport phloem sap?Pressure-Flow Theory

Education

Circulation in plants and animals