part3

DIGESTIVE SYSTEM

 All organisms need energy for their metabolism. They get this energy by nutrition.

 Digestion is the breaking down the food into monomers , making easy the diffusion of

molecules through the membrane.

 Mechanical or physical digestion: It is the breaking down the polymers physically. In

that way the surface area of the substrate is increased. This enables the digestive enzyme

activity.

 Chemical digestion: It is the breaking down the polymers into monomers by the help of

the digestive enzymes.

 Intracellular digestion takes part in cell. To do intracellular digestion, food molecules

should be taken from outside by phagocytosis. Lysosome takes part in this kind of

digestion. Unicellular organisms, some primitive multicellular animals or specialized

cells like liver and white blood cells do intracellular digestion.



 Extracellular digestion takes part out of the cell. To do extracellular digestion, digestive

enzymes are secreted out of the cells. Then digested monomers are taken to the cells by

transport mechanisms. Most of the multicellular animals , fungi, both autotroph

heterotroph plants do extracellular digestion. In that way organisms can use many kinds

of polymers



 Digestion is intracellular in unicellular organisms. Food is taken by phagocytosis. Food

vacuole then unites with the primary lysosome to form secondary lysososme. Food

molecules are broken down by hydrolytic enzymes. Undigested materials are thrown out

of the cell by exocytosis.









 Digestive systems of the invertebrates are adapted according to their nutritional types.

 Sponges make intracellular digestion. Hydra can do both intra and extracellular digestion.

 Parasites like don’t have developed digestive systems because they get their food readily.

Planaria has a primitive digestive system with one opening.

 From the beginning of the class Annelids 2 openings (mouth and anus) can be seen. In the

earthworm digestive system consists of mouth, pharynx, esophagus, crop, gizzard,

intestine, anus.











 Snail has a teeth-like structure called radula.











 Arthropoda has a developed digestive system.

 Filter feeders, such as clams and blue whales, prey on small organisms by filtering them

from the aquatic environment

Digestive system in Vertebrates

 Herbivores, Carnivores and omnivores have different adaptations according to their

nutrition.









 the teeth of herbivorous vertebrates have been shaped by selection to process plant. The

digestive processes of herbivores can also be quite specialized .

 Digestive system is very long in herbivores but short in carnivores. Nonruminant

herbivores(rabbit) have developed cecum which has microorganisms to digest cellulose in

plant tissues.

 The digestive tracts of ruminants (cud chewers) such as cattle, goats, and sheep are

specialized to maximize the benefits of their endosymbiotic microorganisms. They have a

large, four-chambered stomach. The first two chambers, the rumen and the reticulum, are

packed with anaerobic microorganisms that break down cellulose by fermentation. The

ruminant periodically regurgitates the contents of the rumen (the cud) into the mouth for

rechewing. When the more thoroughly ground-up vegetable fibers are swallowed again,

they present more surface area to the microorganisms for their digestive actions.









 Birds don’t have teeth, instead their beaks(bill) help gathering food.

 esophagus - narrow tube that carries food to the crop

 crop - a sack-like widening of the digestive tract where food can be stored temporarily

 proventriculus - the first chamber of a bird's stomach where food is broken down by

digestive enzymes

 gizzard - the second chamber of a bird's stomach where food is ground up by muscular

action and small stones or grit (ingested by the birds)

 intestines -

Human Digestive System

The human digestive system is a coiled, muscular tube (6-9 meters long when fully

extended) stretching from the mouth to the anus. Mouth, pharynx, esophagus, stomach, small

intestine, large intestine, and anus. Accessory digestive organs are connected to the main system

by a series of ducts: salivary glands, exocrine part of the pancreas, liver and gall bladder



 There are 32 permanent teeth

 From the midline of one side of each jaw consists of 2 incisors, 1 canine, 2 premolars and

3 molars









 Mechanical breakdown begins in the mouth by chewing (teeth) and actions of the tongue.

Chemical breakdown of starch by production of salivary amylase from the salivary

glands. This mixture of food and saliva is then pushed into the pharynx and esophagus.

The esophagus is a muscular tube whose muscular contractions (peristalsis) propel food

to the stomach.

 Muscles in the esophagus propel the bolus by waves of involuntary muscular contractions

(peristalsis) of smooth muscle lining the esophagus

 Stomach is lined with epithelial layer which secrete Gastric juice. Gastric juice contains

hydrochloric acid, pepsinogen, lipase and mucus. Secretions are controlled by nervous

(smells, thoughts, and caffeine) and endocrine signals. Mucus covers the inner layer of

stomach and prevents the damage of HCl. HCl activates inactive enzyme pepsinogen and

form pepsin which digests proteins. Small amount of lipase digests lipids.









 The small intestine is where final digestion and absorption occur. The small intestine is a

coiled tube about 6 meters long. The surface area of the small intestine is increased by

villi(fingerlike projections).

 The upper part, the duodenum, is the most active in digestion. Secretions from the liver

and pancreas are used for digestion in the duodenum. Epithelial cells of the duodenum

secrete a watery mucus. The pancreas secretes digestive enzymes and stomach acid-

neutralizing bicarbonate. The liver produces bile, which is stored in the gall bladder

before entering the bile duct into the duodenum.

The liver produces and sends bile to the small intestine via the hepatic duct and vater point . Bile

contains bile salts, which emulsify fats, making them susceptible to enzymatic breakdown.

In addition to digestive functions, the liver plays several other roles:

1) detoxification of blood;

2) synthesis of blood proteins;

3) destruction of old erythrocytes and conversion of hemoglobin into a component of bile;

4) production of bile;

5) storage of glucose as glycogen, and its release when blood sugar levels drop; (stores

ADEK vit.)

6) production of urea from amino groups and ammonia.

 Hepatic portal system , has capillary, vein

capillary, vein structure



 Liver recieves blood from 2 different

supplies.

 Blood rich in digested monomers

comes from the vein from the

intestine. (hepatic portal vein)

 Blood rich in oxygen comes from

the AORT(hepatic artery)

 The pancreas contains exocrine cells that

secrete digestive enzymes(trypsinogen,

amylase, lipase) into the small intestine

and clusters of endocrine cells. The

Langerhans islets secrete the hormones

insulin and glucagon, which regulate

blood glucose.

Digestion of polymers



Don’t forget vitamins, minerals, water can’t be digested and can’t give energy. They are

absorbed without any change.

Mouth: mechanical and chemical digestion



Stomach: mechanical and chemical digestion

pepsinogen HCl pepsin

Duodenum: mechanical and chemical digestion

Gall bladder: Fat bile fat droplet

pancreas: fat droplet Lipase glycerol+fatty acid

starch amylase maltose

peptons Chymotrypsin peptides+ aa

trypsin

Intestine: Chemical digestion and absorption

dipeptid erepsin aa

Maltose maltase glucose sucrose sucrase glucose+fruc

Absorption









Villi and micro villi increases absorption rate. Under the epithelial layer there are blood and

lymph vessels in mucosa.

 Monosaccharides, aminoacids, minerals, water soluble vitamins pass to the blood vessels.

They are carried to the liver by portal vein.

 But fatty acid, glycerol and fat soluble vitamins pass to the lymphatic vessels from the

epithelium. Lymphatic vessels mix with the circulatory system just before the heart.

 Water is absorbed all the way through the digestive system. Minerals and vitamins are

mainly absorbed from large intestine.

 Undigested matter is thrown out by feces.

Pathway of the monomers

glucose, fructose, galactose,

minerals, water soluble Fatty acid, glycerol, fat soluble

vitamins, aminoacids vitamins

 Mesenteric vein from  Lymphatic vessels

intestine

 Hepatic portal vein

 Thoracic duct



 Liver

 Left subclavian vein



 Hepatic vein

 Superior vena cava



 İnferior vena cava

 Right atrium



 Right atrium









Control of digestion

Salivation is stimulated by the sight or smell of

food. That response is an autonomic reflex, as

is the act of swallowing following tactile

stimulation at the back of the mouth. Many

such autonomic reflexes coordinate activity in

different regions of the digestive tract.

Stretching the stomach with food, for

example, stimulates increased activity in the

colon, which can lead to the expulsion of

feces.

The stomach secretes a hormone called

gastrin into the blood. Gastrin circulates in the

blood until it reaches cells in the upper areas

of the stomach wall, where it stimulates the

secretions and movements of the stomach.

secretin is one of several hormones that

control pancreatic secretion; specifically,

secretin stimulates the pancreas to secrete a

solution rich in bicarbonate ions.

In response to the presence of fats and

proteins in the chyme, the mucosa of the

small intestine secretes cholecystokinin, a

hormone that stimulates the gallbladder to

release bile and the pancreas to release

digestive enzymes.

5. Transport and Circulatory Systems

Why are transport and circulation different ?

 Transport is the movement of one molecule from one place to another.

 Circulation is the continous flow of the materials.

Why do we need?

 Transport and circulation are necessary for the movement of molecules that cells need for

metabolism and the molecules that are formed as a result of metabolism. Also they may

help regulation of body temperature and hormonal control.

 Unicellular and simple organisms exchange materials by osmosis, diffusion and active

transport .

TRANSPORT IN PLANTS

 Primitive plants like liverworts, mosses don’t have transport systems. Ferns have

primitive vascular tissues. In higher plants transport occurs in two ways. Water and

minerals are taken by roots and transported to the stem and leaves by xylem. But organic

molecules like glucose are transported from leaves to the roots and from roots to the

leaves by phloem.

 Also stomata are important for the gas exchange and for transpiration.



MONOCOTYLEDONES

 Have closed vascular bundles. There is no cambium. Vascular bundles are scattered in the

stem.

DICOTYLEDONES

 They have open vascular bundles.

 Have cambium between xylem and phloem.

 Vascular bundles are arranged in a circle.







LEAF ADAPTATIONS



 Leaves are the organs where photosynthesis, transpiration and gas exchange occur.

Palisade paranchyma is the most important part in the photosynthesis.

 Stomata are the place where gas exchange occurs ( CO2 intake- O2 release in

photosynthesis, O2 consumption - CO2 release in cellular respiration)

 Epidermal cells secrete waxy substance called cuticle to prevent water loss.



Water transport

Water transport consists of 2 processes:

 Absorption of water from roots(root pressure)

 Transport of water in xylem (in vessels and tracheids)



Within living tissues, the movement of water from cell to cell follows a gradient of water

potential(osmotic pressure). Over longer distances, in xylem vessels and phloem sieve tubes, the

flow of water and dissolved solutes is driven by a gradient of concentration. (bulk flow)

ABSORPTION OF WATER

 Water moves into a root because the root has a higher osmotic pressure than does the soil

solution. Water moves from the cortex of the root into the stele (which is where the

vascular tissues are located) because the stele has a more osmotic pressure than does the

cortex.

The basis for root pressure is a higher solute concentration, and accordingly a more osmotic

pressure in the xylem sap than in the soil solution.









 There is good evidence that root pressure is important and can be observed in the

phenomenon of guttation, in which liquid water is forced out through openings at the

margins of leaves. Guttation occurs only under conditions of high atmospheric humidity

and plentiful water in the soil, which occur most commonly at night.









Transport of water in xylem

 The key elements of water transport in the xylem are

1. Transpiration, the evaporation of water from the leaves

2. Tension in the xylem sap resulting from transpiration

3. Cohesion in the xylem sap from the leaves to the roots

 The concentration of water vapor in the atmosphere is lower than that in the leaf. Because

of this difference, water vapor diffuses from the intercellular spaces of the leaf, through

openings called stomata, to the outside air. This process is called transpiration

 The force generated by the evaporation of water from the mesophyll cell walls creates a

tension that draws more water into the cell walls, replacing that which was lost. The

removal of water from the mesophyll and veins, establishes tension on the entire column

of water within the xylem, so that the column is drawn upward all the way from the roots.

The ability of water to be pulled upward through tiny tubes results from the cohesion of water—

the tendency of water molecules to stick to one another through hydrogen bonding. The narrower

the tube, the greater the tension the water column can withstand without breaking. The integrity

of the column is also maintained by the adhesion of water to the xylem walls.

 Adhesion: sticking together to the different molecules

 Cohesion: sticking together to the same molecules

This transpiration-cohesion-tension mechanism requires no work (that is, no expenditure of

energy) on the part of the plant. (don’t forget that xylem cells are nonliving). At each step

between soil and atmosphere, water moves passively toward a region with a more negative water

potential(high osmotic pressure).



In addition to promoting the transport of minerals, transpiration contributes to temperature

regulation.









TRANSPORT OF ORGANIC MOLECULES

(glucose, amino acids) IN PHLOEM

 Substances in the phloem move from sources to sinks. The flow can be in two directions.

A source is an organ (such as a mature leaf or a storage root) that produces (by

photosynthesis or by digestion of stored reserves) more sugars than it requires. A sink is

an organ (such as a root, a flower, a developing fruit or tuber, or an immature leaf) that

consumes sugars for its own growth and storage needs.

 Sugars (primarily sucrose), amino acids, some minerals, and a variety of other solutes are

translocated between sources and sinks in the phloem. This translocation requires energy.

 Translocation occurs by pressure flow. According to the pressure flow model of

translocation in the phloem, sucrose is actively transported into sieve tube elements at a

source, giving those cells a greater sucrose concentration than the surrounding cells.

Water therefore enters the sieve tube elements by osmosis. The entry of this water causes

a greater pressure potential at the source end of the sieve tube, so that the entire fluid

content of the sieve tube is pushed toward the sink end of the tube— in other words, the

sap moves by bulk flow in response to a pressure gradient. In the sink, the sucrose is

unloaded by active transport.









 specific sugars and amino acids are actively transported into cells of the phloem. In sink

regions, the solutes are actively transported out of the sieve tube elements and into the

surrounding tissues.









QUESTIONS



1. A student set up a potometer and used it to compare the rate of

water uptake in a cut shoot. The first set of readings was taken

on the shady side of the laboratory. The second set of readings

Uptake of water/mm

was taken by the window in bright sunlight, but still in the laboratory.

The readings shown in the table were taken at 30 second intervals in shade in sunlight

and represent the distance, in millimetres, travelled by the water

column in 1 minute. 15 12

15 15

14 19

13 24

12 25

12 26

13 25

(a) Plot a graph to display these results, with time along the

horizontal axis. Show the two sets of results separately on

the same graph starting from time zero in each case.



(b) If the student wanted to compare the average rate of

uptake in each situation, which readings should be used?



(c) Explain your reasoning.





(d) Calculate the two appropriate averages (means) and suggest

why exposure to sunlight seems to affect the rate of uptake.





2. The graph shows the absorption and

transpiration of water by a poplar tree.

water uptake or loss/gm

(a) During which period or periods is transpiration

transpiration more rapid than

absorption?

(b) What would be the effect if this absorption

imbalance were to continue?

(c) During which period or periods is

absorption faster than transpiration?

(d) In these periods, what processes might midday midnight midday

be causing the continued uptake water?

absorption and transpiration by a poplar tree









CIRCULATORY SYSTEM IN ANIMALS

The purpose of the circulatory system in animals:

 Transport of food monomers and gases to the body cells.

 Transport of unnecessary metabolites

 Regulation of body temperature

 Transport of hormones and homeostasis.



ADVANTAGES OF CLOSED CIRCULATORY SYSTEM

 Blood can flow more rapidly through vessels than through intercellular spaces, and can

therefore transport nutrients and wastes to and from tissues more rapidly.

 By changing resistance in the vessels, closed systems can be more selective in directing

blood to specific tissues.

 Specialized cells and large molecules that aid in the transport of hormones and nutrients

can be kept within the vessels, but can drop their cargo in the tissues where it is needed.

 Overall, closed circulatory systems can support higher levels of metabolic activity than

open systems can, especially in larger animals. How, then, do highly active insect species

achieve high levels of metabolic output with their open circulatory systems? One way is

by not depending on their circulatory systems for respiratory gas exchange

Open circulatory system Closed circulatory

system

1. No capillaries and 1. Capillaries and veins

veins are found.

2. Heart/s and artery can 2. Heart/s and artery can

be found. be found.

3. Tissue fluid(blood- 3. Blood never travels

endolymph) travels aout of the blood

out of the bood vessels vessels.

and mixes with the

body fluid.

4. In molluscs, 4. Annelid(earthworm),

arthropoda, insects. cephalopods, all

vertebrates.





A circulatory system is unnecessary if the cells of an organism are close enough to the external

environment that nutrients, respiratory gases, and wastes can diffuse between the cells and the

environment. Small aquatic invertebrates have structures and body shapes that permit direct

exchanges between cells and environment. Many of these animals have flattened body shapes

that maximize the amount of surface area that is in contact with the external environment .



 Large surface areas and branched internal cavities cannot satisfy the needs of larger

animals with many layers of cells. The cells of such animals are surrounded by an internal

environment of extracellular fluids, tissue fluids.



 Insects have open circulatory system. The contractions of the heart propel the tissue fluid

through vessels(small artery) leading to different regions of the body, but the fluid leaves

those vessels to move through the tissues and eventually return to the heart. The fluid

returns to the heart through valved openings called ostia. In these organisms tissue

fluid(blood-endolymph) only carries nutrients. Respiratory gases are carried by tracheal

tubes.

 One large blood vessel on the ventral side of the earthworm carries blood from its anterior

end to its posterior end. Smaller vessels branch off and transport the blood to even

smaller vessels . In the capillaries respiratory gases(mostly around skin), nutrients, and

metabolic wastes diffuse between the blood and the tissue fluid. The blood then flows

from these vessels into larger vessels that lead into one large vessel on the dorsal side of

the worm. The dorsal vessel carries the blood from the posterior to the anterior end of the

body.

 Five pairs of vessels connect the large dorsal and ventral vessels in the anterior end, thus

completing the circuit. The dorsal vessel and the five connecting vessels serve as hearts

for the earthworm; their contractions keep the blood circulating. The direction of

circulation is determined by oneway valves in the dorsal and connecting vessels.









Circulatory system in fish

 The fish heart has two chambers. An atrium receives blood from the body(deoxygenated)

and pumps it into a more muscular chamber, the ventricle. The ventricle pumps the blood

to the gills, where gases are exchanged. Blood leaving the gills (oxygenated)collects in a

large dorsal artery, the aorta, which distributes blood to smaller arteries and arterioles

leading to all the organs and tissues of the body. In the tissues, blood flows through beds

of tiny capillaries, collects in venules and veins, and eventually returns to the atrium of

the heart.









Circulatory system in amphibia

 Pulmonary and systemic circulation are partly separated in adult amphibians. A single

ventricle pumps blood to the lungs and to the rest of the body. Two atria receive blood

returning to the heart. One receives oxygenated blood from the lungs, and the other

receives deoxygenated blood from the body. Because both atria deliver blood to the same

ventricle, the oxygenated and deoxygenated blood could mix, so that blood going to the

tissues would not carry a full load of oxygen.

 These animals supply their oxygen need also by their skin.









Circulatory system in reptiles

 Turtles, snakes, and lizards are commonly said to have three-chambered hearts, while

crocodilians (crocodiles and alligators) are said to have four-chambered hearts. But this

statement is an oversimplification. The hearts of all these animals have two separate atria

and a ventricle that is divided in a complex way so that mixing of oxygenated and

deoxygenated blood is minimized.

 Amphibians and reptiles can not keep constant their body temperature. They are called as

poikilothermic animals.









 The four-chambered hearts of birds and mammals completely separate their pulmonary

and systemic circuits. They keep their body temp. Constant. They are called as

homeothermic animals.

• The four-chambered hearts of birds and

mammals com-pletely separate their pulmonary

and systemic circuits. They kepp their body

temp. Constant. They are called as

homeothermic animals.

Metabolic rate

Body temperature

poikilothermic

poikilothermic



homeothermic

homeothermi

c









Env. Temp.

Env. Temp.









Human circulatory system

 Heart always have deoxygenated blood in the right, oxygenated blood in the left side.

Deoxgenated blood from the body comes first to the right atrium by veins. Blood then

flows to the right ventricle through the tricuspid valve. This valve prevents backflow of

the blood from ventricle to the atrium. Right ventricle pumps the deoxygenated blood to

the lung by pulmonary artery. Arteries always carry blood from the ventricles. The right

heart pumps blood through the pulmonary circuit. The oxygenated blood from the lung

returns back to the left atrium of the heart. The vein who carries the oxygenated blood

from the lung to the heart is called as pulmonary vein.









The oxygenated blood in the left atrium then flows to the left ventricle through mitral(bicuspid)

valve. Then the oxygenated blood is pumped rom the left ventricule to the aorta. The left heart

pumps blood through the systemic circuit. Also the arteries coming out of the heart has valves at

the beginning part. This valve helps the one directional flow of the blood.









Heart is composed of 3 layers. The inner layer is endocard, it is a very thin layer which covers

the inner surface of the heart. It contains epithelial cells and connective tissue.

Myocard: is composed of cardiac muscle. It contains coronery blood vessels.

Pericard: is the outermost layer of the heart. It covers heart as an envelope. It contains fluid

inside this envelope. This layer reduces friction during contractions.

Pulmonary and systemic circulation

 Pulmonary circulation is between the heart and the lungs. Deoxygenated blood is pumped

out of the right ventricle through the pulmonary artery to the lungs and in the lung

capillaries gas exchange occurs. After oxygenated blood is collected by pulmonary vein,

it returns back to the left atrium.









 Systemic circulation is between heart and the body organs. Blood is pumped out of the

left ventricle through the aorta to the body organ arteries. Material(gas, nutrients)

exchange occurs in the capillaries and blood is collected back by veins to the vena cava

and flows to the right atrium.

Mechanism of heart contraction

 The contraction of the two atria, followed by the contraction of the two ventricles and

then relaxation, is called the cardiac cycle. Contraction of the ventricles is called

ventricular systole, and relaxation of the ventricles called ventricular diastole.

 Cardiac muscle has specific properties. First, cardiac muscle cells are in electrical contact

with one another through gap junctions, which enable action potentials to spread rapidly

from cell to cell. This coordinated contraction is essential for pumping blood effectively.

 Second, some cardiac muscle cells are pacemaker cells. These cells have the ability to

initiate action potentials without stimulation from the nervous system.(but speed of

contraction can be controlled by sympathic and parasympathic nerves)The primary

pacemaker of the heart is a nodule of modified cardiac muscle cells, the sinoatrial node,

located at the junction of the superior vena cava and right atrium.









 A normal heartbeat begins with an action potential in the sinoatrial node. This action

potential spreads rapidly throughout the electrically coupled cells of the atria, causing

them to contract. Situated at the junction of the atria and the ventricles is a nodule of

modified cardiac muscle cells called the atrioventricular node, which is stimulated by the

depolarization of the atria. With a slight delay, it generates action potentials that are

conducted to the ventricles by bundle of His. The short delay in the spread of the action

potential imposed by the atrioventricular node ensures that the atria contract before the

ventricles do, so that the blood passes progressively from the atria to the ventricles to the

arteries.









Arteries Veins Capillaries

Takes away the blood Brings the blood to the Material exchange occurs

from the heart heart between blood and

body cells

Large arteries have many Vein walls are not thick Capillary wall is very thin

collagen, elastic fibers and elastic as consists of 1 layer of

and smooth muscle, arteries. Thier epithelial cells. It is

which enable them to diameter is large. semipermeable.

withstand the high

pressures of blood

flowing rapidly from the

heart

Blood moves by the Blood pressure is the Blood pressure is low

pressure created by the lowest in veins

beating of the heart

Blood pressure drops as it Valves within veins and Found between arterioles

travels away from the venules prevent and venules.

heart. backflow

Blood flow speed is high. Blood flow speed is low Blood flow speed is the

lowest in the

capillaries.

Contraction of skeletal

muscles and

absorption force of

heart help blood

movement in the vein

Factors helping the movement of blood in the arteries and arterioles.

 Pressure formed by the contraction of ventricles.

 Contraction of smooth muscle cells in the wall of arteries.

 Pressure gradient

 Pushing force of the blood

Factors helping the movement of blood in the veins and venules

 One way valves

 Contraction of the skeletal muscles around them

 Pressure changes in the chest

 Gravity *pressure gradient

 Absorption force formed by the diastole of the atrium

Blood pressure

 Blood exerts a pressure to the walls of the blood vessels. This pressure is formed by the

systole of the ventricles. Blood pressure decreases as blood travels away from the heart.

Blood pressure increases during systole, decreases during diastole.









Velocity of the blood

Velocity of the blood is affected from the diameter of the blood vessels and the blood pressure.

The velocity of the fluid decreases as it passes from a narrow tube to a wide tube. The velocity is

high in arteries but it decreases as arteries branch into many arterioles. The total cross-sectional

area of the arterioles is bigger than the AORTA, so the velocity is low in arterioles and in

capillaries.

Material exchange between blood and body cells

 Starling suggested that water balance in capillary beds is a result of two opposing forces,

which have come to be known as Starling’s forces. One force is blood pressure, which

squeezes water and small solutes out of the capillaries, and the other is osmotic pressure

created by the large protein molecules that cannot leave the capillaries. Starling called

this second force colloidal osmotic pressure. He hypothesized that blood pressure is high

at the arterial end of a capillary bed and drops steadily as blood flows to the venous end.









 The colloidal osmotic pressure, however, is constant along the capillary. As long as the

blood pressure is above the osmotic pressure, water leaves the capillary, but when blood

pressure falls below the osmotic pressure, water returns to the capillary. The actual

numbers for a normal capillary bed in a resting person suggest that there would be a slight

net loss of water to the intercellular spaces.

Lymphatic circulation









 Lymphatic circulation consists of lymph capillaries, lymph vesses and lymph nodules. It

is a separate system of vessels—the lymphatic system—which returns tissue fluid to the

blood.

 Functions in material exchange. Collects extra fluid.

 Absorbs triglycerides(fatty acids and glycerols) .

 The lymph nodes also act as filters. Particles become trapped there and are digested by

phagocytes in the nodes.

 Lymph nodes are a major site of lymphocyte production and of the phagocytic action that

removes microorganisms and other foreign materials from the circulation

 After entering the lymphatic vessels, the tissue fluid is called lymph. Fine lymphatic

capillaries merge progressively into larger and larger vessels and end in two lymphatic

ves-sels—the thoracic ducts—that empty into large veins at the base of the neck . The left

thoracic duct carries most of the lymph from the lower part of the body and is much

larger than the right thoracic duct. Thoracic duct mixes with blood circulation from the

left subclavian vein.

Lymph, like blood, is propelled toward the heart by skeletal muscle contractions and breathing

movements, and lymphatic vessels, like veins, have one-way valves that keep the lymph flowing

toward the thoracic duct.

QUESTIONS

1. Sometimes the natural pacemaker of the heart fails to work properly and the ability of the heart

to pump blood is impaired. When this happens, a battery-powered artificial pacemaker is

surgically inserted into a person's body. The artificial pacemaker delivers electric shocks at

regular intervals to make the heart beat. What part of the heart is simulated to beat?

A. aorta

B. blood vessels

C. valves

D. muscle tissue



2. Some people suffer from a condition called a heart murmur. This occurs when the valves of

the

heart do not close properly and the blood flows backwards from the ventricles into the atria.

Which of the following shows how knowing about the anatomy of the heart has made treatment

of heart murmurs possible?

A. X-rays are used to determine whether or not the heart is defective.

B. Breathing machines can help humans keep breathing.

C. Artificial valves are used to replace the damaged human valves in the heart.

D. Genetic engineering is used to make insulin to help diabetics.



3. How would the total cross-sectional area of capillaries compare to arteries and veins?

A. Capillaries have more area than arteries

B. Capillaries have less area than veins

C. Capillaries have less area than arteries

D. Capillaries have the same area as arteries

E. Arteries and veins have equal area