Biology 9

Cardiovascular System in Vertebrates (notes)

Consists of heart, vessels, blood

Heart has…

• 1/2 atria chambers that receive blood

• 1/2 ventricle chambers that pump OUT blood

Many have two other chambers

• Sinus venosus — receiving upstream from atrium

• Conus Arteriosus — directs blood out of heart

  • mammals lose as they develop

Arteries carry blood away from heart

Branch into arterioles which then branch into capillaries

Capillaries are microscopic, sites of exchange, leaky

• tight junctions are not so tight

Capillaries join together to form venules which then join to form veins

Veins carry blood toward heart

Circulation in Actinopterygii (notes)

Two chambered heart (one atrium, one ventricle) on ventral (bottom) side of the body

Blood from body —> sinus venosus (low pressure, low oxygen) —> atrium —> ventricle —> Conus arteriosus (high pressure, low oxygen)

• ventricle puts blood under pressure

Blood flows from conus arteriosus into ventral aorta (main artery)

Ventral aorta has four branches on each side that branch upward —afferent branchial arteries

• lead into gill arches —> gill filaments —> gill lamellae —> capillaries in gills

Blood passes from afferent branchial arteries to efferent branchial arteries

(high pressure, low oxygen) —> (low pressure, high oxygen) after moving through capillaries

Blood now moves up to dorsal aorta (main artery)

• most goes posterior to tail

• some goes to brain though

Initially 2 dorsal aortae side by side that fuse into one (just past the gills)

Other arteries that branch from dorsal aorta that go through capillary beds throughout body

• low pressure, high O2 —> lost to low pressure, low O2

Low pressure blood moves through body through muscle contractions

Then cycle restarts

Circulation in Frogs (notes)

Three chambered heart (2 atria (left & right, 1 ventricle)

2 Circuits (Double Circulation) IN ALL TETRAPODS

1. Pulmocutaneous circuit: heart (right) —> respiratory organ —> heart (right)

2. Systemic circuit: heart (left) —> tissue/organs —> heart (left)

high pressure, low O2 as it leaves right ventricle, goes into capillaries of respiratory organs (lungs/skin), low pressure, high O2

blood goes back into heart to left ventricle with low pressure, high O2, then gets pushed into aorta (main artery) — 2 aorta arches that fuse into 1

Ridges separate sides of the ventricle, there’s slight mixing of blood from left and right sides but not enough to affect their health

Circulation in Reptiles (notes)

Ridge separating ventricles is better developed in non-archosaur reptiles

• Similar circulation system to amphibians

Archosaurs have 4 chambered hearts fully separated by walls (ex. crocs, birds, dinos)

• Can shunt blood when they dive — stops sending blood to the lungs

  • shunts pulmonary artery to aorta to BYPASS pulmonary circuit

• Right side receives from systemic and pumps into pulmonary circuit

• Left side receives pulmonary and pumps into systemic circuit

Circulation in Mammals & Archosaurs (notes)

Four chambered heart (2 atria, 2 ventricles)

Atria receive blood only

Ventricles pump blood

No mixing of O2 rich and O2 depleted blood

Double circulation — restores pressure after blood passes through capillaries

Evolution of vertebrate circulation (notes)

Sharks: 6 aortic/gill arches

Teleost Fish (Actinopterygii): lost 2 front arches

Lung fish: retained arch 2 but lost front arch

• 6th arch shunts blood through gills/lungs

Amphibians: lost arches 1,2,5

• arch 3 separated from dorsal aortae (goes anterior) — carotid artery to brain

• arch 4 is aortic arches

• arch 6 = pulmonary arteries to lungs

Reptiles (non archosaur): lost arches 1,2,5

• arch 3 separated from dorsal aortae (goes anterior) — carotid artery to brain

• arch 4 is aortic arches (R & L)

• arch 6 = pulmonary arteries to lungs

Birds (archosaurs): lost 1,2,5 fully

• LOST left of 4 = aortic arch

• arch 3 = carotid artery to brain

• right side of arch 4 = aortic artery

• arch 6 = pulmonary artery to lungs

Mammals: lost 1,2,5

• LOST bottom right of 4 = aortic arch

• arch 3 = carotid artery to brain

• left side of arch 4 = aortic artery

• arch 6 = pulmonary artery to lungs

Subclavian arteries = go to pectoral limbs

• Teleost, Amphibians previously posterior

• Birds and Mammals now anterior

  • Mammal — the left subclavian artery branches directly off the aortic arch

  • Birds — subclavian arteries branch directly from carotid artery

Receives blood from head and upper limbs

Superior Vena Cava

Receives blood from trunk and legs

Inferior Vena Cava

Receives blood from right lung

Right Pulmonary Veins

Receives blood from left lungs

Left Pulmonary Veins

Receives blood from the pulmonary circuit

Left Atrium

Receives blood from the systemic circuit

Right Atrium

Pumps blood to the pulmonary circuit

Right Ventricle

Pumps blood to the systemic circuit

Left Ventricle

Where does left ventricle pump blood out to?

Aorta

Artery that leads blood to the liver

Hepatic Artery

Vein that receives blood from the liver

Hepatic Vein

a different path that leads into the liver and is bound on each end with capillary beds

Hepatic Portal Vessel

Hepatic Portal Vessel and Hepatic Artery exit where?

Through Hepatic Vein —> Vena Cava

Where blood flows to capillary beds in the kidneys

Renal Artery

From where blood goes from capillary beds in the kidney to then after, into the the Inferior Vena Cava

Renal Vein

Blood does NOT move through…

more than one systemic capillary bed or organs

Trace the pathway followed by a short chain fatty acid to a toe cell

Oral cavity

Pharynx

Esophagus

Stomach

Small intestine

Apical PM of mucosa cell

Basal PM of mucosa cell

Interstitial Fluid

Basal PM of capillary cell

Apical PM of capillary cell

Hepatic Portal Vessel

Hepatic Capillary

Hepatic Vein

Vena Cava

Right Atrium

Right Ventricle

Pulmonary Artery

Lung Capillary

Pulmonary Vein

Left Atrium

Left Ventricle

Aorta

Artery in toe

Capillary in toe

Apical PM of Capillary

Basal PM of Capillary

Interstitial Fluid

PM of toe cell

Rhythmic Pumping (notes)

Systole = when blood is pumped from the heart or Contraction

Diastole = when heart fills with blood or Relaxation

Valves prevent backflow of blood in heart

• Atrioventricular Valves (AV) = between atrium and ventricles

• Semilunar Valves (SV) = between ventricles and arteries exiting the heart (aorta/pulmonary artery)

Lub Dub heart sounds caused by the closing of valves

• Lub = atrioventricular valves

• Dub = semilunar valves

Cardiac Output

Volume of blood pumped per minute by left ventricle

Cardiac Output = heart rates * stroke volume

• Heart rate = BPM

• Stroke Volume = blood pumped by left ventricle per contraction

Control of Heart Rhythm (notes)

Myogenic hearts

• most mammals/vertebrates

• no nerve impulse for every contraction

• self rhythm — input from nervous system to modulate what’s going on but they are self excitable

• Sinoatrial (SA) node in right atrium sends electrical signal without input from brain causing muscles in atria to contract

  • Pacemaker

  • Gap junctions allow small molecules to pass through w/o plasma membranes — where charges move through

• Atrium contract before ventricles with a delay of 0.1s — Atrioventricular Node (AV)

• electric currents detected at surface —EKG

Neurogenic hearts

• nerve impulse required for every contraction of heart

Electrical signals of the heart/brain are…

movement of charges (charged ions)

Arteries and Veins layer makeup

3 layers

1. outer layer of connective tissue

2. middle layer of smooth muscle — vasoconstriction and vasodilation

3. inner layer of single, simple, squamous epithelium called ENDOTHELIUM

When smooth muscle decrease diameter of blood vessel

Vasoconstriction

When smooth muscle relaxes and increases diameter of blood vessel

Vasodilation

Capillary makeup

1 layer of endothelium

tight junctions aren’t very tight

has pores between cells that allow exchange between IF and blood

______ have valves along system to prevent backflow

Veins

Blood Flow (notes)

Flow rate remains constant always because narrower canals have faster Velocity

Velocity

• high in arteries

• low in capillaries

  • total cross section area is larger so velocity drops

• moderate in veins — regains speed

Blood Pressure = hydrostatic force that blood exerts against a vessel wall

• pressure is high in arteries (ventricles creates greater blood pressure which directly move to aorta/artery)

• drops as it moves through capillaries and never regained

• in veins pressure is NEAR zero

  • valves prevent backflow

blood flow to capillaries controlled by nerves and hormones

Exchange in Capillary Beds (notes)

O2 and CO2 diffuse down concentration gradient

However small materials can leave through leaky capillary walls as pressure from blood pushes things out

• small materials include salts, water, amino acids, and vitamins

• concentration of small materials equal inside and outside

• large materials include blood proteins

Because large materials aren’t naturally diffusing out, blood proteins stay in blood and contribute to osmotic pressure

Direction of Flow in Capillaries (notes)

Dependent on the balance between hydrostatic pressure and osmotic pressure

Osmotic Pressure depends on solute concentration

• overall solute conc. (includes small and large materials): there’s more solutes in the blood

• Osmotic Pressure in blood > in interstitial fluid

Arteriole side of capillary bed = net flow out

Venule side of bed = net flow in

85% of fluid leaving arteriole end of capillary reenters at venule end

15% eventually returned by lymphatic system = parallel circulatory system without RBC

• low pressure — no O2 content

• has valves to prevent backflow

• propagated along by contraction of skeletal muscles

• will enter back into bloodstream near shoulders

• has lymph nodes for immune function to filter and attack bacteria or viruses (WBC)

Movement of Fluid Between Capillaries and Interstitial Fluid

As blood enters capillary (arterial end)

blood pressure is 32 mm Hg (based on hydrostatic pressure: force that blood exerts against a vessel wall)

Osmotic pressure is 22 mm Hg (based on blood proteins/remains constant)

32 mmHg - 22 mmHg = 10 mmHg net pressure moves out

Because materials move out, blood pressure drops to 15 mmHg

15 mmHg - 22 mmHg = -7 mmHg net pressure moves in

This is towards the venous end of capillary as blood moves out

Blood (notes)

connective tissue consisting of…

• cells (45%)

• liquid matrix called plasma (55%) that suspends cells

Plasma

• 90% water

• electrolytes — inorganic salts (ions), maintains osmotic balance

• plasma proteins — escort lipids, antibodies, clotting factors

• serum — plasma without clotting factors

• nutrients

• metabolic wastes

• gases

• hormones

Cellular Elements

• erythrocytes = RBC

  • no mitochondria to use up O2!

  • contains 250 × 10^6 molecules of hemoglobin

• leukocytes = WBC

  • include lymphocytes and neutrophils

• platelets = cell fragments used in clotting

Cellular Components of Blood

Multipotent Stem Cell in Red Marrow (in bone)

• branches into…

  • Myeloid stem cell

  • Lymphoid stem cell

• Myeloid — innate (first line of defense)

  • platelets

  • erythrocytes

  • basophil

  • eosinophil

  • neutrophil

  • monocyte/macrophage

• Lymphoid — adaptive (acquired defense)

  • Lymphocytes: B and T

Blood Clotting (notes)

Injured blood vessel —> chemicals release

• platelets attach by being made to be “sticky”

• clotting factors are activated — Prothrombin (inactive) to Thrombin (enzyme)

• Thrombin targets fibrinogen (zymogen) peptide linkage which activates it to fibrin

• Once activated fibrin is not soluble and precipitates out, it forms a net that holds platelets in place

• Clotting occurs with trapped cells

Cardiovascular Diseases (notes)

heart attack = death of heart muscle due to blockage of coronary arteries

• blockage prevents certain sections of muscles from getting nutrients it needs —> that part of the muscle dies

stroke = death of neural tissues in brain

• could be caused by clogged artery or breakage of artery

heart muscle and neurons not replaceable

Thrombus = clot

Embolus = moving clot

• thrombus breaks off and floats until it plugs up stream of capillary beds

Atherosclerosis = plaques in inner walls of arteries

• chronic disease

• clot that accumulates fatty acids, macrophages, and cholesterol —> cutting down diameter of artery

Arteriosclerosis = plaque hardens by calcium deposits

Fat connection: too much cholesterol ☹

• LDL (low density lipoproteins) in blood lead to deposition of fats and cholesterol in plaque

Hypertension (high blood pressure) promotes atherosclerosis

Osmoregulation (notes)

Maintaining homeostasis requires maintaining correct water and salt balance

• avoid wide fluctuations in ion conc. and pH

• animals can’t survive large fluctuations

• too much H2O = cells burst

• too much H2O loss = cells shrivel and die

Osmosis: diffusion H2O across semipermeable membrane from high water conc. to low water conc.

• hyposmotic = low solute

• isosmotic = equal solute

• hyperosmotic = high solute

Osmoconfomers (notes)

Animals who evolved in the ocean are considered osmoconformers

Does not adjust internal osmolarity

• extracellular fluid/interstitial fluid is isosmotic to ocean water (equal solute conc)

• many differ in ion ratios from sea water: ionoregulators and ionoconformers

  • Ionoconformer = exact same concentration and ratios of ions from surroundings (interstitial fluid is basically sea water)

  • Ionoregulators = requires energy expenditure for ions to be pumped across membranes against their gradients

    • Osmoconformers-ionoregulators ECF has the same total ion conc. as sea water

Osmoregulators (notes)

internal ECF not isosmotic to sea water

ALL osmoregulators are ionoregulators

• requires energy!

adjusts internal osmolarity by adjusting solute concentration

• special transport epithelium required to regulate ion conc., pH, and water conc.

• NO PUMPS for water on cell/tissue level

• water moved by osmotic gradients

SOME marine, ALL freshwater, and all terrestrial animals

Vertebrates: evolutionary example

Marine vertebrates originally isosmotic (hagfish, lampreys. ancestors of Gnathostomata)

Gnathostomes moved in to FRESH water habitats

• I.F. has become hyperosmotic (adapted from salt—>fresh water)

• water will actively move into body through skin but mostly through gills

• Adaptations:

  • large amounts of dilute urine (prevents overhydration as water keeps coming in)

  • uptake of salts to ensure they maintain proper amounts of ions

  • decrease solute conc. of body fluids (lowers energy expended to maintain homeostasis)

Some groups move back to ocean (SALT water)

• I.F. has become hyposmotic

• water will actively move out of body

• Adaptations:

  • drinks large amounts of water (balance out water lost)

  • pumps excess salt out through gills (to balance the increased salt intake from drinking sea water)

  • small amount of concentrated urine

Salmon gills readapted each time they move from freshwater, salt water, and freshwater again

Metabolic Waste (notes)

Metabolism of proteins and nucleic acids produces nitrogenous wastes

• NH3 highly toxic

• amino acids have to be deaminated —> collection of NH3 must be rid of because it’s virtually useless

• NH3 is very soluble in water

In small animals, simple diffusion gets rid of metabolic waste

In large animals, cells are not in contact with environment

• requires special organs to remove waste

• Excretion = rids body of waste material INSIDE body

  • Elimination = rids body of undigested waste that was never in your body in the first place

• Excretion of nitrogenous waste evolved secondarily

Aquatic animals usually excrete NH3

Terrestrial animals

• to get rid of metabolic waste, salt and water loss always occurs

• Some animals combine 2 waste products

  • Urea = CO2 and NH3 which is less toxic and conserves water

  • Uric Acid = far less toxic than NH3, low solubility in water (solid waste, less water wasted, more energy required)

Most animals have a combo of Urea, Uric Acid, and NH3 in different amounts

Primary Osmoregulatory Adaptations of Arthropods, Vertebrates, etc., to conserve water

Behavioral Adaptations — thirst, brain pushes you to drink water

Excretory organs conserve water

• mostly birds and mammals — hyperosmotic urine

Impervious covering that prevents water loss

• Arthropods — waxy layer on exoskeleton, cuticle

• Vertebrates — layers of dead keratinized cells

  • base cells are cuboidal and divide, pushing other cells up which eventually die and accumulate

Organs for osmoregulation/excretory systems

Dependent on transport epithelium

solutes/ion actively pumped

Water follows osmotic gradients

Types:

A. Protonephridia

B. Metanephridia

C. Malpighian tubules

D. Mammalian Kidney

Protonephridia

simplest system

branched system of closed tubes lacking internal openings — only has openings to outside body

• tubes of simple cuboidal epithelia

Primarily used for osmoregulation (excretion by simple diffusion across body wall)

Ex. Flatworms (Platyhelminthes)

• protonephridia inside body capped by flame bulb cell

• cilia beat INSIDE fame bulb to produce pressure to move fluid through tubules

• opening on wall of body where urine is excreted

Processes:

• Filtration (non selective, except for size) —

  • nothing can differentiate small molecules: amino acid, salt, nitrogenous waste molecule

• Reabsorption (selective, returns to hemolymph) —

  • requires active transport

  • pumps move glucose back from urine into hemolymph

• Secretion (selective, adds to filtrate) —

  • materials that are too concentrated in hemolymph, filtering doesn’t work (ex. hydrogen ions)

  • actively transported across protonephridia

• Initial fluid is hemolymph but just the small particles which moves through the protonephridia where it is chemically changed by reabsorption and secretion so that when it reaches the opening, what comes out is the finished, hypsomotic urine

Metanephridia

Slightly more complex than protonephridia

in annelids, Oligochaeta — right and left metanephridia on each segment

Openings both on inside of body and body wall

Nephrostome — opening into interstitial fluid

• in one segment, it’s surrounded by capillary beds

• second segment purifies I.F. in preceding segment

Has some filtration, reabsorption of salts and other metabolites, and secretion

Hyposmotic dilute urine + nitrogenous waste handled (unlike in protonephridia)

Nephridiopore — opening to outside

• one on each side of each segment

Malpighian Tubules

In insects

Filters hemolymph

Blind tubes connected to junction between midgut and hindgut

Driving force is H+ ATPase in apical membrane of epithelium

Malpighian Tubule Secretion

1. H+ ATPase (apical): pumps H+ into lumen of tube

• HIGH [H+] in lumen, LOW [H+] in cell

2. H+/K+ cotransporter (apical): protons naturally follow gradient back INSIDE cell, meanwhile co-transporting K+ OUT of cell and into lumen

• HIGH [K+] in lumen, LOW [K+] in cell

3. Chlorine Channel: Chlorine follows and neutralizes positive charge

4. K+/Na+/2Cl- cotransporter (basal): moves 1 K+, 2 Cl-, 1 Na+ into lumen

• balanced charges

• driving force is K+ gradient, naturally moves into cell

• 2 Cl- and Na+ move through channels into lumen

As this occurs, water moves through aquaporins (pores for water)

• Water follows salts, as it moves into lumen, other nutrients may flow in too (bulk flow)

• Water can only move DOWN tube into gut

Some stuff can be reabsorbed in proximal tubule

• amino acids, sugars

Primary urine enters midgut — rich in K+, Na+, Cl-

Water and salts reabsorbed in rectum

Malpighian Tubules Reabsorption in Hind Gut

1. Cl- ATPase (apical) — creates low conc. of Cl- inside lumen, high conc. of Cl- inside cell

2. Chlorine Channel (basal)— facilitates movement of Cl- from inside cell to hemolymph

3. Na+/K+ ATPase (basal) — 3 Na+ pumped out to hemolymph and 2 K+ pumped in

• creates low Na+ concentration in cell

4. Sodium Channel (apical) — facilitates movement of High [Na+] in lumen to Low [Na+] in cell

5. As Na, K, and Cl moves, water moves down gradient into cell

• Water gets removed from lumen/gut, waste becomes more concentrated

• Uric acid precipitates

6. K+ channels (apical and basal) — maintains balance as other ions move?

Mammalian Kidneys

Compact organ with excretory tubes

For excretion and osmoregulation (major organ for balancing pH)

Blood goes into renal artery —> kidneys (where blood is filtered) —> renal vein —> vena cava

Filtered waste goes from kidneys —> ureter —> bladder —> urethra —> urine

Structure: 2 major layers

• outer cortex

• inner medulla

• contains nephrons (filtering unit?) and collecting ducts (simple cuboidal epithelium)

Nephron

Bowman’s Capsule (simple squamous) empties into proximal tubule

It makes two sharp turns forming the Loop of Henle — proximal tubule descends down into medulla and then ascends up into distal tubule

Distal tubule connects to collecting duct that goes deep into medulla —> renal pelvis —> ureter —> bladder

Kidney Blood Supply into Nephron

Afferent arteriole —> Glomerulus (bowman’s capsule capillary beds) —> Efferent arteriole —> Peritubular Capillaries (capillary beds that surround proximal and distal tubules) —> Vasa Recta (net of capillary beds that surround Loop of Henle) —> venule —> renal vein

Loop of Henle and Vasa Recta run counter current to each other