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Animal form and function (Circulation and gas exchange (Single circulation…
Animal form and function
Circulation and gas exchange
Circulatory systems link exchange surfaces with cells throughout the body
Gastrovascular cavities
Cnidarians
Functions in the distribution of substances throughout the body, as well as in digestion
Circulatory systems
Heart
A muscular pump that powers circulation by using metobolic energy to elevate the circulatory fluids hydrostatic elevation
Circulatory fluid
A set of interconnected vessels
Open circulatory system
Circulatory fluid is also the interstitial fluid called hemolymph
Closed circulatory system
Circulatory fluid called blood is confined vessels and is distinct from the interstitial fluid
Cardiovascular system
The closed circulatory system of humans and other vertevrates
Arteries
Carey blood from heart to organs
Capillaries
Microscopic vessels with thin porous walls
Veins
Vessles that carry blood back to the heart
Venules
Capillaries converge into venules which converge into veins
Arterioles
Arteries branch out into arterioles which then become capillaries
Atria
The chambers of the heart that recieve the blood entering the heart
Ventricles
The chambers responsible for pumping blood out of the heart
Single circulation
Bony fiah, rays and sharks
Heart consists of 2 chambers, an atrium and a ventricle
Blood passes through the heart once in each complete circuit through the body
Blood entering the heart collects in the atrium before transfer to the ventricle.
Contraction of the ventricle pumps blood to a capillary bed in the gills, where there is a net diffusion of O2 into the blood and of CO2 out od the blood
Blood leaves the gills the capillaries converge into a vessel that carries o2 rich blood to capilary beds throughout the body.
Blood then returns to the heart
Double circulation
Amphibians , reptiles,and mammals have 2 curcuits
The pumps for the two circuits are combined into a single organ called the heart
Having both pumps within a single heart simplifies coordination of pumping cycles
One pump, the roght side of the heart delivers o2-poor blood to the capillary beds of gas exchange tissue where there is a net movement of O2 into and co2 out ofthe blood
Pulmonary circuit
Capillary beds involved are all in the lungs
Pulmocutaneous circuit
Capillaries in both the lungs and the skin: amphibians
Systemic circuit
The left side of the heart recieves the o2 rich blood
Contraction of the heart propels this blood to capillary beds in organs and tissues throughout he body
Following the exchange of o2 and co2 as well as nutrients and waste
Oxygen poor blood returns to the heart
3 types of hearts
Single circulation
Fish
2 chambered heart
O2 poor blood comes up from capillary beds in body into veins to the atrium then to the ventricle then blood travels to the capillary beds in the gills where blood is oxyginated and taken to the bodys capillary beds
Double circulation
Amphibian
3 chambered heart
2 atria and one ventricle
A ridge within the ventricle about 90% of the oxygen rich blood from the left atrium into the systemic circuit and most of the oxygen poor blood from the right atrium into the pulmoctaneous circuit
Mammals
4 chambered heart
2 atria and 2 comoletely divided ventricles
Left side of the heart recieves and pumps only o2 rich blood while right side recieves and pumps only o2 poor blood
Cardiac cycle
One complete sequence of pumping and filling
Cardiac output
Volume of blood each ventricle pumps per minute
Heart rate
Rate of contractions
Stroke volume
Amount of blood pumped by a ventricle in a single contraction
Blood pressure
Blood flows from areas of higher pressure to lower pressure
Contraction of a heart ventricle generates blood press
Systolic pressure
When arterial blood pressure is highest when heart contracts during ventricular systole
Each spike in blood pressure caused by ventricular contraction streches the arteries
Pulse
Rythmetic bulging of the artery walls with each heartbeat
Diastolic pressure
The elastuc walls of the arteries snap back
There is lower but still substantial blood pressure when the ventricles are relaxed
Regulation
Vasoconstriction
Smooth muscles in arteriole walla contract and arterioles narrow
Narrowing of the arterioles increases blood pressure upstream in the arteries
Vasodilation
Smooth muscles relax and arterioles undergo an increase in diameter that causes blood pressure in the arteries to fall
Normal human values
120 mm Hg systole and 70 mm Hg diastole
Lynphatic system
A network of tiny vessels intermingled among capillaries of the cardiovascular system as well as larger vessels into which small vessels empty
Lymph
Fluid lost by capillaries
About the same composition of interstitial fluid
Lymph nodes
Lymph filtering organs
Connective tissue that holds white blood cells
Drains into large veins at the back of the neck and enables lipids to be transferred from the snall intestines to the blood
Blood
Connective tissue consisting of cells suspended in a liquid matrix called plasma
Cells and cell fragments occupy about 45% of blood and the rest is plasma
Plasma has ions and proteins tahys function with blood cells in osmotic regulation, transport and defense.
Plasma
Inorganic salts in the form of dissolved ions sometimes referred to as blood electrolytes
Ions are important in maintaining the osmotic balance of the blood
Cellular elements
Red blood cells
Transport o2
White blood cells
Defense
Platelets i
Suspended in plasma
Clotting process
Erythrocytes
Red blood cells
Every microliter of blood contains 5-6 million red cells
Contain hemoglobin
Iron containing protein that transports o2
Leukocytes
Basophils
Lymphocytes
Eosinophils
Neutrophils
Monocytes
Fight infections
Respiration
Partial pressure
Pressure excreted by a particular gas in mixture of gases
Reapiratory organs
Gills
Outfildings of the body surface suspended in the water
Ventilation
Maintains the partial pressure gradients of o2 and co2 across the gill that are necessary for gas exchange
Countercurrent exchange
The exchange of a substance or heat between 2 fluids flowing in opposite directions in fish
Lungs
Localized respiratory organs
Infolding of the body surface
Not in direct contact w other parts of body so gap must be bridged by circulatory system for gas exchange
Trachea branches into 2 bronchi
Bronchi branch repeatedly into finer tubes called bronchioles
At the tips of bronchioles are aveoli which are air sac clusters
Skin
Amphibians
Diffusion across external body surfaces to carry out gas exhcange
Breathing
Alternating inhalation and exhalation of air
Amphibians
Positive pressure breathing
Infating the lungs with forced airflow
First stage of inhalation the muscles lower the floor of the amphibians oral cavity drawing air throigh its nostrils
Nostrils and mouthclose and floor of oral cavity rises forcing air down trachea
Exhalation air is forced back out the elestic recoil of the lungs and by compression of the muscular body wall
Mammals
Negative pressure breathing
Pulling air into the lings
Uses muscle contractions to actively expand the thoracic cavity
Lower air pressure in their lings below that of the air outside their body
Gas flows from a region of higher pressure to a region of lower pressure
Air rushes through the nostrils and mouth and down the breathing tubes to the aveoli
During exhalation muscles controlling the thoracic cavity relax and the volume of the cavity is reduced
Increased air pressure in the aveoli forces air up the breathingtubesand out of the body
Inhilation always requires work while exhalation is usually passive
Osmoregulation and excretion
Osmosis
The movement of water from hypotonic solutions to hypertonic solutions
Osmoregulation
Process by which animals control solute concentrations and balance water gain and loss
Osmolarity
No. Of moles of solute per liter of solution
Osmoconformer
Isoosmotic with surroundings
Osmoregulator
Control internal osmolarity independent of thay of the external environment
Marine animals
Most invertebrates are osmoconformers
Their osmolarity is the same as that of sea water so they face no substantial challenges in water balance
Mist actively transport solutes to maintain homeostasis
Vertebrates and some invertebrates are osmoregulators
For most of these animals the ocean is a strongly dehydrating environment
Freshwater animals
Body fluids of freshwater animals must be hyperosmotic bc animal cells cannot tolerate salt concentrations as low as that of lake or river water
Internal fluids with an osmolarity higher than that of their surroundings, they face a problem of gaining water by osmosis and losing salts by diffusion
Excretion
Ammonia
Animals who excrete nitrogenous waste as ammonia need access to a lot of water because ammonia can be tolerated only at very low concentrations
Very common in aquatic species
In many invertebrates, ammonia release occurs across the whole body surface
Not suitable for land animals
Metobolic nitrogenous wastes
Urea
Because most terrestrial animals and many marine species simply do not have access to sufficient water to routinely excrete ammonia they mostly excrete urea
In vertebrates it is the product of a metobolic cycle that combines ammonia with carbon dioxide in the liver
Advantageous bc it has very low toxicity
Disadvantagous bc of energy cost
Uric acid
Insects, snails and many reptiles and birds
Relatively nontoxic and does not dissolve in water
Very little water loss
Even more energetically expensive than urea and requires consideable ATP for synthesis from ammonia
Excretory organs
Protonephridia
Flatworms
A network of dead end tubules
Tubules which are connected to external openings branch throughout the flatworm body which lack coelom
Cellular units called flame bulbs cap the branches
Metanephrida
Most annelids
Collect fluid directly from the coelom
Each segment of an annelid has a pair of metanephrida which are immersed in coelomic fluid enveloped by a capillary network
A cilliated funnel surrounds the internal opening of each metanephridium
As the cilia best fluid is drawn into a collecting tubule which includes a storage bladder that ooens to the outside
Malpighian tubules
Insects and other terrestrial arthropods
Extend from dead end tips immersed in hemolymph to openings into the digestive tract
Transport epithelium that lines the tubules secretes certain solutes including nitrogenous wastes from the hemolymph into lumen of the tubule
Water follows the solutes into the tubules by osmosis and the fluid then passes i to the rectum
There most solutes are pumped back into hemolymph and water reabsorbtion by osmosis follows
Kidneys
Vertebrates and some chordates
Consist of tubules areanged in a highly organized manner and are closely associated w a network of capillaries
In humans excretory system consists of kidneys , ureter, urinary bladder and urethra
Nephrons
Functional units of the vertebrate kidney
Juxtamedullary nephrons
Essential for production of urine that is hyperosmotic to body fluids and a key adaption for water conservation in mammals
Proximal tubule
Reabsorbtion crutial for recapturing ions, water, and valuble nutrients from the huge volume of initial filtrate
NaCl in the filtrate enters the cells of the transport epithelium by facilitated diffusion and contrasport mechanisms
Epithelial cells actively transport Na to the interstitial fluid
Water follows by osmosis
Salt and water then diffuse from the interstitial fluid into the peritubular capillaries
Essential substances are also actively or passively transported from the filtrate to the interstitial fluid and then into the peritubule capillaries
Filtrate passes through the proximal tubule materials to be excreted becomes concentrated
Decending limb of the loop of henle
Reabsorbtion of water continues as the filtrate come into the decending limb
Numerous water channels formed by aquaporin proteins make rhe transport of epithelium freely permeable to water
For water to move out of the tubule by osmosis the interstitial fluid bathing the tubule must be hyperosmotic to the filtrate
Filtrate loses water and increases in solute concentration
Ascending limb of the loop of henle
Filtrate reaches the tip of the loop and then returns to the cortex in the ascending limb
Has a transport epethilium that lacks water channels
Has 2 specialized regions
Thin segment near the loop tip
Thick segment adjacent to distal tubule
Filtrate becomes progressively more dilute as it moves up the cortex in the ascending limb of the loop
Distal tubule
Regulates K and NaCl concentrations in the body fluids
Collecting duct
Carried the filtrate through the medulla to the renal pelvis
Final processing of the filtrate by the transprot epithelium of the collecting duct forms the urine
Hormonal control of permeability and transport determines the extent to which the urine becomes concentrated