BISC 101 Lecture Notes - Lecture 16: Superior Vena Cava, Pulmonary Circulation, Pulmonary Vein

108 views9 pages
BISC 101 – Lecture 16 – Circulation and Gas Exchange: Part I
Circulatory Systems
Circulatory systems link exchange surfaces with cells throughout the body
Every organism must exchange materials with its environment
oExchanges ultimately occur at the cellular level
Diffusion time is proportional to the square of the distance
oDiffusion is only efficient over small distances
In small and thin animals, cells can exchange materials directly with the surrounding
medium
In most animals, cells exchange materials with the environment ia a fluid – filled
circulatory system
Gastro vascular Cavities
Some animals lack a circulatory systems
oEx: Cnidarians like jellyfish and hydra, and flatworms have elaborate gastro
vascular cavities
A gastro vascular cavity functions in both digestion and distribution of substances
throughout the body
Body wall enclosing the gastro vascular cavity is only two cell layers thick
Open and Closed Circulatory Systems
More complex animals have either open or closed circulatory systems
Both systems have three basic components
oCirculatory Fluid: Blood or hemolymph
oSet of tubes: Blood vessels
oMuscular pump: The heart
The circulatory system connects the fluid that surrounds cells with the organs that
exchange gases, absorb nutrients, and dispose of wastes
,Open Circulatory System: Blood flows freely within the body cavity/sinuses and bathes
the organs directly
oEx: Insects, arthropods and most molluscs
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 9 pages and 3 million more documents.

Already have an account? Log in
oAll the blood is not enclosed in blood vessels
oBlood is pumped into a cavity called a hemocoel, where the blood mixes with the
interstitial fluid
oHemolymph: Blood mixed with interstitial fluid
oAs the heart beats and the animal moves, the hemolymph circulates around the
organs within the body cavity and then re – enters the heart
Closed Circulatory System: All of the blood is confined to blood vessels and is separate
from the interstitial fluid
oBlood travels uni – directionally in vessels
oClosed systems are more efficient at transporting circulatory fluids to tissues and
cells
oThe heart sustains a high pressure necessary for the blood to reach all of the
extremities of the body
Organization of Vertebrae Closed Circulatory Systems
Humans and other vertebrates have a closed circulatory system, often called the
cardiovascular system
The three main types of blood vessels are
oArteries: Blood flow away from the heart, most arteries carry oxygenated blood
except the pulmonary artery
oVeins: Blood flow towards the heart, most veins carry deoxygenated blood ,
except the pulmonary vein
oCapillaries: Exchange of O2, CO2, nutrients, and waste between blood and body
tissues
Arteries branch into arterioles and carry blood to capillaries
Capillary Beds: Network of capillaries that is the site of chemical exchange between the
blood and interstitial fluid
Venules converge into veins and return blood from capillaries
Vertebrate hearts contain two or more chambers
Blood enters through an atrium and is pumped through a ventricle
Single Circulation
Bony fishes, rays, and sharks have single circulation with a 2 – chambered heart
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 9 pages and 3 million more documents.

Already have an account? Log in
In single circulation, blood leaving the heart passes through 2 capillary beds
During one complete cycle of flow through the body, blood passes through the heart only
once
Double Circulation
Amphibians, reptiles and mammals have double circulation
Deoxygenated and oxygenated blood are pumped separately from the right and left
sides of the heart
During one complete cycle of flow through the body, blood passes through the heart
twice
Double circulation maintains higher blood pressure in the organs than does single
circulation
Sufficient blood pressure is needed to send blood from the heart then eventually back to
the heart
Blood pressure is higher in larger animals in which since blood must move large
distances around the body before it arrives back at the heart
Animals that have double circulation systems need blood to be supplied to their tissues
quickly due to their high metabolic rates
This need ensures sufficient blood flow because the transport functions of blood include
supplying the tissues with O2 and nutrients needed to continue activities including
chemical reactions
Amphibians
Oxygen – poor blood flows through a pulmocutaneous circuit to pick up oxygen through
the lungs and skin
Frogs and amphibians have a three chambered heart
o2 atria and 1 ventricle
The two atria receive blood from the two different circuits
oPulmocutaneous and systemic
Some mixing of the blood in the hearts ventricle is present which reduced the efficiency
of oxygenation
The ventricle pumps blood into a forked artery that splits the output into both circuits
This circulation has the ability to re – direct blood to the skin instead of the lungs when
underwater
Reptiles
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 9 pages and 3 million more documents.

Already have an account? Log in

Get access

Grade+
$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
1 Booster Class
Class+
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
1 Booster Class