Circulatory System

Updated 4 November 2004

Function - transports respiratory gases, nutrients, metabolites, water, hormones, heat (gain/loss); closely associated with all other organ systems

Components

A. Lymphatic system - collects excess fluid from tissues; drain into blood-vascular system (one-way, A®B flow)

B. Blood-vascular system - heart, vessels, blood (circular, A®B®A flow)

1. Vessels - arteries, veins, capillaries (exchange; large surface area), portal veins (DRAW)

a. individual variation in development (especially small vessels, DRAW)

b. heart and major vessels less variable among individuals; useful in phylogenetic studies

2. Hemodynamics (slide 1, slide 2); blood distribution - importance of microcirculation (capillary beds + arterioles + venules)

Circulation patterns – single vs. double circulation (slide 3)

Embryonic circulation (basic vertebrate pattern ); slide 4

A. Heart (DRAW) sinus venosus, atrium, ventricle, conus arteriosus

B. Vessels (DRAW)

1. Arteries – ventral aorta, aortic arches, dorsal aorta (branches to inner/outer tubes)

2. Veins – anterior cardinals, posterior cardinals, common cardinals, vitelline veins

Vessels

A. Arteries

1. Aortic arches (slide 5, slide 6, slide 7, slide 8) - carotids, pulmonary v., carotid duct, ductus arteriosus, systemic arch

2. Branches of systemic aorta

a. median ventral (viscera) - celiac, mesenteric

b. paired ventrolateral (urogenital) - renal, genital

c. paired dorsolateral (somatic tube) - vertebral, subclavian, iliac, deep circumflex, cranial abdominal

B. Veins (slide 9 – embryonic development in a mammal)

1. Anterior cardinals (anastomose) - cranial vena cava

2. Posterior cardinals (+ subcardinals, hepatic) - posterior vena cava, renal portal (not in mammals)

3. Vitelline, subintestinal - hepatic portal

4. Phylogenetic patterns (slide 10, slide 11, slide 12)

Heart

A. Phylogenetic trends (embryonic slide 13, S-shape)

1. Septa in AT, V (slide 14)

2. SV incorporated into AT

3. CA divide into trunks and incorporated into V

B. Taxonomic survey

1. Most fish: similar to embryonic heart, single circuit (slide 15; S-shape)

2. Tetrapods (air-breathing) requires two separate circuits

a. amphibians (also dipnoans) (slide 16, slide 17)

b. complete interatrial septum; no (or incomplete) interventricular septum

c. little ventricular mixing (streams functionally separated within V)

d. exceptions: plethodontids - no interatrial septum (cutaneous respiration only – served by branches of systemic aorta); Necturus (perennibranch; interatrial septum reduced or perforated)

3. Reptiles (2 patterns)

a. most reptiles (turtles, squamates) slide 18, slide 19

1) complete interatrial septum; partial interventricular septum; compartmentalized (little mixing)

2) SV reduced

3) CA incorporated into V (pulmonary trunk, R and L systemic trunks)

4) cardiac shunting R«L (adaptive advantages) – READ

b. crocodilians (slide 20)

1) complete separation (interatrial and interventricular septa), except for Foramen of Panizza

2) SV reduced

3) CA incorporated into ventricles (pulmonary trunk, R and L systemic trunks)

4. Mammals, birds

a. complete separation (interatrial and interventricular septa)

b. very small SV (mostly incorporated into RA)

c. CA incorp into ventricles (pulmonary trunk, systemic trunk)

d. changes at birth (closures, re-route blood flow) slide 21

1) interatrial foramen

2) ductus arteriosus

3) ductus venosus

C. Phylogenetic variation in morphological patterns - how study?

1. Trace flow (by taxon and age); practice drawing; DEMO

D. READ - heat transfer: heat blocks, retes, countercurrent exchangers