Blood Vessels1) heart2) liver3) gut4) kidney

A: Arteries1) carotid artery2) subclavian artery3) pulmonary artery4) hepatic artery5) aorta6) mesenteric artery7) renal artery8) iliac artery

B: Veins13) jugular vein14) subclavian vein15) hepatic vein16) vena cava17) hepatic portal vein18) renal vein19) iliac vein

The Double Circulatory System

oxygenated blood

deoxygenated blood

Arteries, Veins and Capillaries

Microscopic Structure

Blood in the Circulatory System

pressure

speed

total cross-sectional area of the vessels

Capillary Exchange

lymph

tissue fluid

tissue cells

capillary

blood

lymph capillary

A B

C D

Tissue Fluid region Ψp

(kPa)Ψs

(kPa)net

pressure

(kPa)A 4.5 -3.3 +1.2

B 1.8 -3.3 -1.5

C 1.0 -1.3 -0.3

D 1.0 -1.3 -0.3

tissue fluid

blood flow

A B

C D

• At the arterial end – formation of tissue fluid

• At the venous end - return of tissue fluid

• Improved exchange with tissues

• Excess fluid returns – as lymph - in the lymphatic system

The Lymphatic System • a drainage system

• part of the immune system

• assists absorption of lipids in the intestine

Blood Plasma (55%) -

– water– proteins (e.g. albumin, globulin,

fibrinogen)– salts (e.g. NaCl, K+, Ca++,

Mg++, PO4-)– transported substances (e.g.

glucose, urea)

Cells (45%) –– erythrocytes (red blood cells)– leucocytes (white blood cells)

• neutrophils: granular phagocytes.

• lymphocytes: produce antibodies.

• monocytes: agranular phagocytes.

• eosinophils and basophils: granular cells concerned with inflammation reactions.

– thrombocytes (platelets): cell fragments

thrombocytes

erythrocytes

lymphocyte

neutrophil

Defence Against Disease1: preventing entry

• skin• tears, saliva and

mucus• lysozyme • stomach acid. • clotting

mechanism to repair skin damage - - - - -

thromboplastin from damaged

tissues

prothrombin(plasma protein)

fibrin(insoluble)

fibrinogen(soluble plasma

protein)

thrombin

Ca++ andplasma enzymes

fibres trap blood cells and platelets to form

a clot

Defence Against Disease2: phagocytosis

The phagocytic cell recognises a foreign particle...

...and engulfs it...

...forming a phagosome.

The particle is digested inside the phagosome...

...and the cell may become an antigen-presenting cell.

Defence Against Disease3: specific immune response

antigen-binding site

antigen-binding site

variable region

constant region

light chain

heavy chain

“hinge” disulphide bridges

antigen-antibody

complexes

specific antibodies

antigen macrophage(antigen-presenting cell)

B-lymphocyte

T-lymphocyte

clonal expansionclonal expansion

antigen presentation

clonal selection clonal selection

T-helper cells

T memory cells

plasma cells

cytotoxic T cells

cytokines

B memory cells

antibodies

humoral immune response

cellular immune

response

Primary & Secondary Immune Responses

Types of ImmunityNatural immunity: normal biological processes - NOT human intervention.

Artificial immunity: due to human (medical) intervention.

Active immunity: the body is exposed to antigen. The immune system produces memory cells giving long-term protection.

E.g., you do not suffer from chicken-pox twice

E.g., vaccination against measles

Passive immunity: the body receives ready-made antibodies. Protection is only short-term.

E.g., antibodies cross the placenta from mother to fetus

E.g., injection of tetanus antitoxin

Rejection – the ABO Blood Group System –

recipient

donor

O A B ABO - - - -A + - + -B + + - -AB + + + -

+ = agglutination occurs- = agglutination does not occur

Haemolytic Disease of the Newborn

• First pregnancy:– No blood-blood contact, so

anti-D antibodies are not formed.

• At birth:– There may be blood-blood

contact, and the mother may form anti-D antibodies.

• Second pregnancy:– The mother already has anti-D

antibodies. These can cross the placenta, and attack the red blood cells of the fetus.

Antibiotic Action

. . ..

. . ..

DNA RNA

ribosomes

inhibition of cell wall synthesis eg penicillin *

inhibition of transcription eg rifampicin *

inhibition of protein synthesis

eg tetracycline †

interference with metabolic reactions eg sulpha drugs † change in membrane

permeability eg polymyxin *

*bacteriostatic antibiotics stop/slow bacterial growth†bacteriocidal antibiotics kill bacteria

Antibiotic Resistance

. . ..

. . ..

cell wall surrounded by impermeable outer envelope (eg in gram negative bacteria)

extra quantities of blocked chemicalsare synthesised

phosphorylation of antibioticprevents it binding to ribosomes/enzymescell membrane

impermeableto antibiotic

enzyme destroysthe antibiotic(eg penicillinase)

blocked chemicalsare absorbed fromthe environment

The Digestive System

Balanced Diet Substance FunctionsCarbohydrates (Sugars/starch)

Energy release (substrates for respiration). Excess energy stored (as glycogen) or converted to fat.

Lipidsfats (solids) and oils (liquids).

Energy/energy storage. Also thermal/electrical insulation, mechanical protection, membrane synthesis (essential fatty acids)

Proteins Growth/repair (structural proteins), enzymes, etc, etc

Mineral ions Various inorganic ions, needed in small amounts for miscellaneous functions.

Vitamins Various organic molecules, needed in small amounts for miscellaneous functions.

Water A constituent of all body fluids, including cytoplasm; water losses (in sweat etc) must be replaced.

Dietary fibremostly cellulose.

Indigestible material - maintains peristalsis.

Important mineral ions needed in the diet

Mineral Food

sourcesFunctions Deficiency

Calcium (Ca++)

Dairy foods, bread

Bones & teeth; muscle contraction, blood clotting, synapses.

Rickets, osteomalacia

Iron (Fe++) Meat; green vegetables.

In haemoglobin; also in electron carriers.

Simple anaemia

Phosphate(PO4

3-)In nearly all

foodsIn bones & teeth; also for ATP, nucleic

acids, cell membranes.-

Magnesium (Mg++)

Green vegetables, etc.

In bones & teeth; also as an enzyme activator in respiration.

Weakening of bones.

Sodium chloride (NaCl)

Table salt, meat.

In blood etc; essential for nerve & muscle action; lost in sweat.

Muscle cramp

Potassium (K+)

In nearly all foods

Enzyme co-factor; essential for nerve & muscle action.

-

Iodine (I-) Seafood In thyroxine. Goitre

Important vitamins needed in the diet

Vitamin Food sources Functions Effect of

deficiencyA: Retinol, or carotene (pro-vitamin A)

Fish oils, liver, dairy produce; and green vegetables

Maintenance of epithelia, esp. mucous membranes; rhodopsin synthesis (in the retina).

Night blindness; drying of epithelia; xerophthalmia.

B1: Thiamine Vegetables, wholemeal cereals, meat.

A co-enzyme for decarboxylation in respiration

Beriberi (nerve & muscle affected).

B2 :Riboflavin Eggs, dairy produce. Synthesis of FAD. Causes sores in/around the mouth.

B3: Nicotinic acid(niacin)

Wholemeal cereals, potatoes, meat.

Synthesis of NAD. Pellagra (skin rashes, diarrhoea).

B9: Folic acid Green vegetables, fish, liver.

Formation of nucleic acids; cell division (esp. red blood cells formation).

Anaemia (esp. during pregnancy)

B12: Cobalamin Meat, liver, dairy produce, eggs.

Formation of nucleic acids; cell division (esp. red blood cells formation).

Pernicious anaemia.

C: Ascorbic acid Most fruits and vegetables

Maintenance of connective tissue. Synthesis of collagen fibres.

Scurvy (bleeding & weakening of gums & skin).

D: Calciferol Egg yolk, dairy produce. [Also can be synthesised in the skin in sunlight.]

Absorption of calcium and phosphate from the gut, and deposition of these minerals in bones and teeth

Rickets in children (bones fail to calcify); osteomalacia (softening of the bones) in adults.

Digestion in the Alimentary Canal

• Physical digestion (chewing, etc): – increases surface area

• Chemical digestion: – hydrolysis of large molecules to soluble products

Polysaccharides Monosaccharides

Lipids Fatty acids & glycerol

Proteins Amino-acids

(INSOLUBLE) (SOLUBLE)

Digestive Secretions

Gland Secretion Enzymes etc Effectsalivary

glands saliva amylase starch → maltose (partly)

gastric glands

gastric juice pepsinogen (endopeptidase)

prorennin

protein → polypeptides [must be converted to pepsin first]

in infants: coagulates milk (caseinogen → casein) [must be converted to rennin first]

HCl pepsinogen → pepsinprorennin → rennin

pancreas pancreatic juice

amylaselipase

starch → maltose (completed)fats → fatty acids & glycerol

trypsinogen (endopeptidase) larger polypeptides → smaller polypeptides [must be

converted to trypsin first]exopeptidases polypeptides → amino-acids

liver bile bile salts emulsify fatsintestinal

glands intestinal juice exopeptidases

enterokinasepolypeptides → amino-acidstrypsinogen → trypsin

maltasesucrase lactase

maltose → glucosesucrose → glucose + fructoselactose → glucose + galactose

Control of Digestive SecretionsBuccal cavity• nervous control - simple reflex • conditioned reflexes

Gastric secretion• cephalic phase –

– presence of food in the buccal cavity– simple neural reflex

• gastric phase 1 – – presence of food in the stomach– local neural reflex

• gastric phase 2 –– presence of food in the stomach– hormonal secretion from stomach wall – gastrin – operates via the blood stream

• intestinal phase –– entry of food into the duodenum– hormonal secretion from duodenal wall –

enterogastrone– inhibitory

Secretion into the small intestine • triggered by presence of food in the duodenum• local neural reflex stimulates secretion of intestinal juice• secretion of hormones into the blood -

– pancreozymin causes secretion of pancreatic enzymes– secretin causes secretion of alkali from the pancreas &

liver– cholecystokinin (CCK) causes contraction of the gall

bladder

• prevents auto-digestion

• prevents wasteful secretion

Absorption of NutrientsMost nutrients are absorbed in the lower part of the small

intestine – Features to note – • large surface area

– villi– microvilli (in cell

membranes of the epithelial cells)

• single-celled epithelium

• dense capillary network

• lacteals for absorption of fats

Mechanism of Absorption• Partly by diffusion• Assisted by active transport – e.g. co-transport

Carbohydrates• some absorbed as monosaccharides (glucose, etc)• some disaccharides absorbed onto the cell membranes, followed by

enzymic hydrolysis

Proteins • absorbed partly as amino-acids• some dipeptides/tripeptides taken onto the cell membranes, with digestion

completed by the epithelial cell.

Lipids • absorbed as fatty acids & glycerol, also as emulsified mono-/di-/tri-

glycerides• mostly absorbed into lacteals – some into the capillaries

Food that has been absorbed into the bloodstream is transported first to the LIVER, in the hepatic portal vein.

Assimilation of Food in the Liver

Homeostasis • The maintenance of an approximately

constant internal environment.

• Homeostasis is important because – – It prevents the denaturing of enzymes– It provides the optimum conditions for metabolic

processes– It makes organisms independent of conditions in the

external environment– Species with efficient homeostatic processes are able to

exploit a wider range of habitats than others.

Homeostatic mechanisms use negative feedback

SET POINT

TOO HIGH

TOO LOW

Sensor

Sensor

Effector

Regulator

Regulator

Effector

external environmen

t

increase

decrease

decrease

increase