Circulatory System – General Aspects - PowerPoint Presentation

Slide1

Circulatory System – General Aspects

In small invertebrate organisms, no circulatory system is necessary, as diffusion distances are short.

With greater size, diffusion from the external environment becomes insufficient and a circulatory system is required to transport materials within the body.

Slide2

Circulatory System – General Aspects

Two

types of circulatory systems are present among invertebrates:

Open System

= more primitive, heart pumps blood out through vessels to various parts of the body. Return vessels are absent so blood oozes back to heart via interstitial spaces.

Closed System

= advanced condition, also present in all vertebrates; blood never leaves vessels. Delivery of nutrients occurs via diffusion across thin-walled capillaries

.

Amphioxus shows intermediate condition = both outgoing and return vessels present, but no capillaries connecting them.

Slide3

Slide4

Fig 12.4

– Microcirculation in a closed vascular system

Slide5

Functions of Circulatory System

Facilitate

gas

exchange

Delivery

of

nutrients

Removal

of

wastes

Transport

of

hormones

 

3

Subcomponents (all

mesodermal in origin

):

Blood Vascular System

= includes heart, arteries (carry blood away from heart), capillaries (gas and nutrient exchange), and veins (carry blood back to heart

)

Hemopoietic

Organs

= sites of blood cell production

Lymphatic System

= thin-walled vessels that carry fluid from interstitial spaces back to blood stream

Slide6

Fig 12.2

– Blood pressure and cross-sectional areas of the different vessels of the blood vascular system.

Slide7

Fig 12.11

– Basic vertebrate blood vascular system circulation, as illustrated in a shark

Slide8

Single and Double Circulation

Fishes

= possess single circulation pattern

Blood passes through heart only once during each complete cycle

Sequence: Heart

 Gills

 Body  Heart

Amniotes

= possess double circulation pattern

Blood passes through heart twice during each complete cycle

Sequence: Heart



Lungs  Heart

 Body 

Heart

Intermediate condition with characteristics of both present in lungfish, amphibians and some reptiles

Slide9

Fig 12.6

– Single and double circulation circuits in vertebrates

Slide10

Developmental Anatomy

General

Principles

:

Main vessels develop in association with major centers for metabolic activity.

Primitive adult conditions are demonstrated in transitory embryonic stages in advanced vertebrates.

“

Ontogeny recapitulates

phylogeny

” works well for the circulatory system.

Slide11

Developmental Anatomy

Developmental Stages

Primitive Condition

= heart pumps blood anteriorly through ventral aorta



passes through paired aortic arches



into paired dorsal aortae



to capillary network of yolk sac



drain to vessels leading back to heart.

Yolk

sac

is site of formation of first blood vessels and first blood cells in the embryo.

Systemic Arteries

branch off dorsal aortae to supply developing organs and gut.

Each

organ develops a capillary bed that merges into systemic veins leading back to heart.

Yolk Sac

is

supplied and drained

by systemic veins (

Portal System)

in

Osteichthyes

and Amphibians. Yolk sac supplied via

Vitelline

Arteries

and drained by

vitelline

veins in

Chondrichthyes

and Amniotes.

Slide12

Developmental Anatomy

Developmental Stages

As the

Liver

develops, it is supplied by veins leaving the yolk sac (=

Hepatic Portal System

) which pass through the liver capillary network then coalesce into veins passing back to the heart.

In Amniotes the

Allantois

(=

extraembryonic

membrane functioning in waste storage) develops and is supplied by

allantoic

artery and drained by

allantoic

vein.

Allantoic

vein initially passes directly to back of heart, but later becomes incorporated into capillary bed of liver. Some anatomical bypass of liver capillary network in birds and reptiles, but not in mammals.

Associated with nutritional role of

chorioallantoic

membrane of the placenta in mammals. Functions solely in respiration in birds and reptiles.

Slide13

Developmental Anatomy

Accessory Circuits

Embryonic stages of all

vertebrates

except most primitive (cyclostomes) possess a

Renal Portal System

supplying capillary beds of kidney.

Renal Portal System also present in all adult vertebrates, except for cyclostomes and mammals, although in birds and reptiles much of the portal supply bypasses the kidney capillary network.

Aortic Arches

shift from gill circulation positioned on main aortic trunk (gill-breathers) to side circuit associated with other structures (lung-breathers).

Slide14

Slide15

Blood

A specialized connective tissue in which the intercellular material is entirely fluid (plasma)

Plasma components include …

Stable components

= inorganic salts and blood proteins (e.g.,

albumin

= increases osmotic pressure of blood,

fibrinogen

= clot formation,

globulins

= immunological role).

Fluctuating components

= glucose, fats, amino acids, waste products (e.g., urea, uric acid), hormones

Slide16

Blood Cells

No blood cells present in Amphioxus

Restricted to low energy lifestyle

Two general categories in all vertebrates:

Erythrocytes

(RBCs) = involved in oxygen and carbon dioxide transport

Hemoglobin serves as respiratory pigment to dramatically increase O

2

carrying capacity of blood

Leukocytes

(WBCs) = many actions – immunological, phagocytic, etc.

Most of these roles accomplished outside of circulatory system

Use circulatory system for transport to sites of action

Slide17

Leukocytes (WBCs)

Unlike RBCs, leukocytes contain nucleus and all other subcellular organelles

Have capacity for

ameboid

movement, many of WBC functions are carried out after movement across vessel wall =

diapedesis

Slide18

Other Blood Cell Types

Platelets

= disc-shaped cell fragments derived from megakaryocytes in bone marrow

Function in clotting

Found only in mammals

Thrombocytes

= spindle-shaped cells developmentally related to WBCs

Function in clotting

Found only in non-mammalian vertebrates

Slide19

Human Blood Smear

Anucleate

erythrocyte

Platelet

Neutrophil (a WBC)

Slide20

Frog Blood Smear

Nucleated erythrocyte

Thrombocyte

WBC

Slide21

Hemopoietic (blood-forming) Tissues

Formation of blood cells continues throughout lifetime (from stem cell precursors) to replace dying blood cells

.

Embryonic Blood-forming

Sites:

Blood Islands in yolk sac in large-

yolked

eggs

Chorion

of placenta in mammals

Becomes more localized later in embryonic development:

kidney (sharks to reptiles and birds)

liver

spleen

thymus (not in hagfish ?)

diffuse sites in intestinal walls

Slide22

Hemopoietic (blood-forming) Tissues

Adult Blood-forming Sites

Spleen (except for mammals and birds)

Thymus (T-lymphocytes)

Kidney (lampreys, elasmobranchs,

teleosts

)

Gonads (elasmobranchs



leukocytes)

Liver (

teleosts

, amphibians, turtles)

Intestinal Walls



lymphoid elements (or walls in other regions of digestive tract – esophagus, pharynx, appendix)

Bone Marrow (amphibians [frogs] – mammals)

Bursa of

Fabricius



lymphoid elements (birds) = dorsal pouch off of cloaca (combined urinary-reproductive-anal opening)

Slide23

Bone Marrow

Embryonic Liver

Arrows = adipose cells

Arrows = developing blood cells

Hemopoietic

Tissues – Myeloid Tissue

Slide24

Lymphatic System

Functions

to return interstitial fluid to blood stream

Lymphatics not connected with arteries; have blind capillaries and vessels.

In

Cyclostomes and Sharks

there is no typical lymphatic system.

Instead

possess an open system of sinusoids (low

b.p

., so low interstitial fluid production in these groups).

Teleosts

possess paired lymph hearts (muscular structures along lymphatics and at junctions with veins that help propel lymph along vessels) and 2 major sets of ducts:

Paired

subvertebral

ducts (deeper)

Paired lateral ducts

A similar condition occurs in Tetrapod embryos.

Slide25

Lymphatic System

Amphibians

with well-developed lymphatic system, many with numerous lymph hearts

Reptiles

show complex system; reduction in the number of lymph hearts and development of valves in vessels to prevent backflow

Birds & Mammals

generally have no lymph

hearts

in adults (although present in bird embryos and in a few adult birds).

Series

of valves present to prevent backflow.

Movement

of lymph in conjunction with skeletal muscle contraction.

Slide26

Lymphatic System

Intestinal region lymphatics particularly well developed in advanced vertebrates.

Most

of the fats entering circulation from the gut do so by way of the lymphatics (due to the large size of the fat molecules and the incomplete endothelial lining of lymphatic vessels, fatty lymph =

chyle

).

Lacteals

= lymphatic vessels leaving intestine carrying

chyle

.

Thoracic Ducts

= lymphatics running along back of body cavity, serve as collectors for lacteals.

Major

duct in mammals (single, paired in many primitive vertebrates).

Cisternae

chyli

= area where many tributaries feed into thoracic duct (occurs in lumbar region)

Slide27

Fig 12.46

– Formation of lymph

Slide28

Fig 12.49

– Lymphatic system in a salamander. Note the prominence of the lymph hearts for moving lymph within the lymphatic system.

Slide29

Fig 12.48

– Lymphatic system in turtles

Slide30

Figure 12.47

Fig 12.47

– Lymphatic circulation and lymph nodes

Slide31

Valve in Lymph Vessel in mammal

Lymph vessel

Flow

Valve

Adipose tissue