1. Lecture 9b:
Circulatory System

2. Circulatory System
Used to transport nutrients and O2 to
cells, and to remove CO2 and waste
Some animals do not need circ. system
because the cells are exposed to watery
environment and are close to each other;
things can pass via diffusion
TMBG video

3. Open system
Found in Arthropods and some other
invertebrates
Heart-like pump moves hemolymph
through arteries to the body, and it then
drains back to the heart
The heart is essentially open to the body
when it is relaxed, closed to the body
when it contracts

4. Closed system
What all vertebrates have
Blood is always contained inside the system and
does not drain into the body unless there is an
injury
Heart: anatomy on board
Arteries: Carry blood away from heart
Veins: Carry blood to the heart
Capillaries: Exchange materials with tissue fluid

5. 3 kinds of vertebrate systems
Fish: One circuit loop
Amphibians and most reptiles: two
circuit loops, but only one ventricle
Crocodilians, birds, mammals: two
circuit loops, 2 atria and 2 ventricles

6. Human
heart

7. Human Heart- Blood flow
From body Lungs
RA LA
RV LV
To body

8. Heart
Each chamber of the heart is separated
from the other
Between each side is the septum
Between each atria and ventricle are
valves - keep the blood from flowing
backwards

9. Heartbeat
Without the pumping action, the heart is
useless
Each beat consists of a series of events
called the cardiac cycle
Atria contract, ventricles contract, rest
Contraction is called systole
Relaxation is called diastole

10. Heartbeat
The beat is controlled by a pacemaker, the SA
node (sinoatrial)
Automatically sends out an impulse that
causes atria to contract, and signals the AV
node (atrioventricular)
The AV node then sends out a signal for the
ventricles to contract
The beat is intrinsic to the heart, but it can be
influenced by outside factors, hormones, etc.

11. Blood vessels
Arteries- transport blood away from the
heart
Heart creates pressure to send blood
into the arteries- this is what blood
pressure is
Have layer of smooth muscle inside to
help provide elasticity

12. Blood vessels
Arteries branch into arterioles, smaller arteries
Diameter can be regulated by nervous
system, to change blood pressure
Arterioles branch into capillaries, microscopic
tubes - only one RBC can pass through them
at a time
Occur in beds, all cells are less than 1mm
from a capillary

13. Blood Vessels
Venules collect blood from the capillaries- these are
small veins
Venules come together in veins, which return blood
to the heart
Veins have much less blood pressure, they are
thin
Skeletal muscles help move blood through the
veins
Veins have valves that prevent back flow

14. Two Circuits
Pulmonary circuit- O2 poor blood is sent
from the heart to the lungs, where it is
oxygenated and returned to the heart
Systemic circuit- O2 rich blood is sent
from the heart to all of the body, where
O2 is removed for cellular respiration,
and then returned to the heart

15. Lymphatic System
This system has several functions
One main function is to collect excess
tissue fluid and return it to the blood
Does this by connecting to the
subclavian veins in the shoulders
Fat is also collected from the digestive
system and delivered here

16. Lymphatic System
Lymphatic vessels are extensive and occur
throughout the body
Similar to veins in that:
they are thin
skeletal muscles cause fluid to move
they have valves to prevent backflow
System is a one-way flow- capillaries to larger
vessels to the lymphatic ducts, which go into the
subclavian veins

17. Cardiovascular Disorders
Hypertension - leading cause of premature
death in US
High blood pressure
BP = systolic/ diastolic
systolic- pressure during contraction
diastolic- pressure during relaxation
Normal = 120/80

18. Hypertension
Accumulation of fatty deposits called
plaque in the blood vessels interferes
with the flow of blood = atherosclerosis
Prevention includes low fat diet, no
smoking or excessive drinking, plenty
of exercise

19. Hypertension
Effects of plaque:
Thrombus- clot that forms where the plaque causes an
irregular shape
Embolus- a clot that breaks free and moves with the blood
flow
Stroke- caused when a cranial arteriole bursts or is
blocked by an embolus, leading to lack of O2 to part
of the brain
Heart attack- when an embolus (or emboli) blocks
coronary arteriole, preventing blood flow to the heart
itself

20. Blood
Functions of blood:
1. Transports things to the capillaries
to exchange with tissue fluid
2. Defend the body against pathogens
3. Helps regulate body temperature
4. Forms clots to prevent catastrophic
blood loss from an injury

21. Plasma
The liquidy stuff!
Mostly water
Also some proteins, salts, nutrients that
help to keep the pH stable at 7.4
The other components also serve to
maintain osmotic pressure so that
water will flow into the capillaries

22. Formed Elements
Red blood cells, white blood cells, platelets
RBC’s: contain hemoglobin, which is
made from iron, gives the red color
Transport O2 to the cells
Made inside bones: skull, ribs,
vertebrae, and the ends of long bones
Do not have a nucleus

23. Formed Elements
WBC’s: leukocytes- help fight infection
Large, do have a nucleus
Can move in and out of the capillaries, so can be
in tissue fluid and lymph as well as in blood
Some live a very short time, others can live for
years
Some engulf and destroy invaders- neutrophils
Lymphocytes- produce antibodies- one per cell

24. Formed Elements
Platelets: thrombocytes- formed when large cells break
up in the bone marrow
Used in blood clotting:
There are at least 12 factors that participate in the
formation of a clot
The loss of just one can lead to the inability to
form clots- can be life threatening
Clots are not just for cuts and scrapes- minute
tears appear all the time and are repaired
internally

25. Capillary exchange
Exchange occurs because of two pressures at work in
the capillary: blood pressure and osmotic pressure
Blood pressure causes water to exit capillaries at the
arteriole end
Osmotic pressure causes water to enter at venule end
In between, pressures are about equal
Passive diffusion causes wastes to enter and
nutrients to exit