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Circulation

11/11/2007

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Circulation

The circulatory systemI. General plan

II. Blood

III. Heart

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Circulation

Movement of blood results from: Force imparted from contractions of the heart Elastic recoil of the arteries following filling

by cardiac contraction Squeezing of blood vessels during body

movements Peristaltic contractions of the smooth muscle

surrounding the blood vessels

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4Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

A chamber pump ( with valves) :

-Has a contractile wall ,or

-Compressed by around muscle

this vessel has valves for unidirectional flow

Heart types

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In human muscle to move blood against gravity

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2 -Peristaltic pump

-Without valves

-Ex, Insect

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CirculationI. General plan

Two main types of circulatory systems1. Open circulatory system

Present in many invertebrates Blood pumped by heart empties into a

hemocoel Hemolymph bathes tissues directly Large volume (20-40% of body volume) Low pressure (4.5-9.7 mm Hg) Limited ability to alter velocity and

distribution of blood flow5

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Open Circulatory System

Artery Veins

There is no distinction between blood and interstitial fluid, collectively called hemolymph.

Fig 42.2

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• In insects, other arthropods, and most mollusks, blood bathes organs directly in an open circulatory system.

• One or more hearts pump the hemolymph into interconnected sinuses surrounding the organs, allowing exchange between hemolymph and body cells.

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• In insects and other arthropods, the heart is an elongated dorsal tube.

– When the heart contracts, it pumps hemolymph through vessels out into sinuses.

– When the heart relaxes, it draws hemolymph into the circulatory through pores called ostia.

– Body movements that squeeze the sinuses help circulate the hemolymph.

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Circulation

2. Closed circulatory system• Vertebrates and some invertebrates (e.g.

cephalopods)• Blood flows in a continuous circuit• Small volume (5-10% of body volume)• High pressure (can attain pressures of > 100

mm Hg)

• Permits high O2 uptake

• Allows for ultrafiltration at the kidneys

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Closed Circulatory System

Interstitial Fluid: fluid directly bathing cells of the body – distinct from blood.

Artery

Veins

Capillaries

Blood

Fig 42.2

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CirculationBasic components of a closed circulatory

system A main propulsive organ (heart)- forces blood

through the body An arterial system- distributes blood and serves

as a pressure reservoir Capillaries- transfer of materials between blood

and tissues Venous system- returns blood to the heart and

serves as a storage reservoir

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• In a closed circulatory system, as found in earthworms, squid, octopuses, and vertebrates, blood is confined to vessels and is distinct from the interstitial fluid.

– One or more hearts pump blood into large vessels that branch into smaller ones cursing through organs.

– Materials are exchanged by diffusion between the blood and the interstitial fluid bathing the cells.

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Closed Circulatory System • In a closed circulatory system

– Blood is confined to vessels and is distinct from the interstitial fluid

Figure 42.3b

Interstitialfluid

Heart

Small branch vessels in each organ

Dorsal vessel(main heart)

Ventral vesselsAuxiliary hearts

(b) A closed circulatory system

Closed systemsare more efficient at transporting circulatory fluids to tissues and cells.

Earthworm an annelid is the first time we see a closed circulatory system!

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Blood capacity

• The higher oxygen capacity of blood , the less volume needs to be pumped.

• See figure 3.25- p(122).• Invertebrate 30% B.W• Vertebrate 5-10% B.W• Control by :• PUMPING FREQUENCY • STROK VOLUME

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• The body plan of a hydra and other cnidarians makes a circulatory system unnecessary.

– A body wall only two cells thick encloses a central gastrovascular cavity that serves for both digestion and for diffusion of substances throughout the body.

• The fluid inside the cavity is continuous with the water outside through a single opening, the mouth.

• Thus, both the inner and outer tissue layers are bathed in fluid.

Many invertebrates have a gastrovascular cavity (or) / a circulatory system for internal

transport

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Phylum Cnidaria gastrovascular cavity is fluid filled and ciliated may branch into tentacles

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• In cnidarians like Aurelia, the mouth leads to an elaborate gastrovascular cavity that has branches radiating to and from the circular canal.

– The products of digestion in the gastrovascular cavity are directly available to the cells of the inner layer, and it is only a short distance to diffuse to the cells of the outer layer.

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• Planarians and most other flatworms also have gastrovascular cavities that exchange materials with the environment through a single opening.

– The flat shape of the body and the branching of the gastrovascular cavity throughout the animal ensure that are cells are bathed by a suitable medium and diffusion distances are short.

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Annelid plan:

• Closed circulation • Respiratory pigments ( HB,

Chlorocurin,hemocyanin )• Earth worm :• Highly vascularized surface.• Two main blood vessel :Dorsal propel blood forward Ventral propel reverse

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Several blood vesel have dilations ( contractile)

These connection blood vessels act as accessory heart

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-Annelids

Figure 17.19

Mouth

Brain

Accessory hearts

Main heart

Coelom

Nerve cord

Digestive tract

Blood vessels

Segment walls

Excretory organ

Anus

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Giant earth worm

Dorsal B.V contract ( peristaltic) 6-8/min

BP= 20 mm.Hg

Five pairs lateral hearts contract after dorsal to give 75mm.Hg

Largest animal without respiratory system 120cm length, 2-3cm dim

500g wight

its Hb po250%= 7mm.Hg

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Echinoderms

• Star fish , sea urchins, sea cucumber …

• Has three fluid system :

a- Coelomic , b- Hemal (blood) , c- Water

Coelomic between skin and digestive system

For transport nutrients

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water Vascular system

• In sea star

• From outside to madreporite to stone canal to ring canal to radial canal to ampulla to tube foot .

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• Have a water vascular system that facilitates gas exchange and waste disposal

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• Sea cucumber have hb and high oxygen affinity PO50% = 5-10 mm.Hg( depend-T)

• Boher effect not exist between 7.5-6.6 Ph

-,Not sensitive at this stage

Because it’s mud is low O2 .

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Mollusca

• Except: squid , and octopus

-All mollusca have an open circulatory system

-With hemocyanin or hemoglobin

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OPEN CIRCULATORY SYSTEM Mollusca

Have well developed hearts , heart rat according to its need

for oxygen.

-Acetylcholine from nervous system to inhibit heart.

-Serotonin excitatory

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• Movement: wavelike muscular contractions of the foot move gastropods smoothly over surfaces

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Blood act as hydraulic fluid of clams and snails

By large blood sinus in foot

Two-chambered heart of a mollusk Helix(snail) an open system

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- Closed circulatory ( arteries and veins)

- It might be related to respiratory gills and to Form a renal pressure 75mm.Hg.

- Blood 6% separated about interstitial fluids15%.

- Other mollusks ( open 50%) because mixed of both blood and fluid

- Blood distributes according to O2 consuming

what about closed mollusks , cephalopods (octopus and squid)

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Insects

• Blood vessel along dorsal side

Posterior parts as heart and with valves opening

Anterior part called aorta

Contractile to propels blood forward

Peristaltic wave

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Pulsating organ : accessory hearts in antenna , legs and wings

Longitudinal membrane to diffusion of blood

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• After aorta blood paths to other parts not by vessel.

• Low B.P no respiratory function .

- Aliform muscle around the dorsal heart contract dorsal heart wider by suction will be filled

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• These are from groups of arthropods Arachnids, such as spiders, scorpions, ticks, and

mites

Arachnids

Figure 17.22

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• In many invertebrates ( open)

• Heart pumps blood into hemocoel – open fluid space- either called blastocoel

• The fluid in hemocoel called hemolymph or blood and reach tissue by bathing not by vessels

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• Spider and scorpion

• -similar to insect but have respiratory role

Hemocyanin in scorpion

With respiratory organs ( lung books)

Blood pressure --- hydraulic for foot expansion

In jumping spider has BP=400mm.Hg

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Insect - scorpion

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Crustaceans, such as crabs, lobsters, crayfish, shrimps, and barnacles

Figure 17.23

Crustaceans

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• Open , and partially open circulatory system.• The smallest one without developed circulation • Lobster , crabs , Cray fish ------(decapods)• Good circulation + respiratory pigment

( hemocyanin) • Has gills

• Dorsal heart in pericardial sinus with ostia

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Crustacean circulation

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• From heart :

- Anterior aorta forward

- Posterior aorta backside

- To branches for tissues.

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Partially open system - Lobster

Gill circuit is enclosed, Feeds hemolymph back to heart

Heart pushes hemolymph out through anterior and posterior arteries

Hemolymph flows into sinuses

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• Heart O2 blood to tissues

Gills oxygenation

While in fish heart receive deoxygenated blood and pumps it to gills then to tissues

and reverse to heart .