Feralis Ch 3 Flashcards
Tissues
Groups of cells that have similar structure and function together as a unit
Types of tissues
Epithelial (skin or internal organ covering), connective (bone, cartilage, blood), nervous, and muscle
Negative feedback
Bringing conditions back to their normal or homeostatic function
Positive feedback
An action that intensifies a condition so that it is driven further beyond its normal limits (ex. Labor contraction, lactation, or sexual orgasm)
Respiration
Movement of gases in and out; can also mean cellular respiration in which ATP is produced in the mitochondria
Thermoregulation
Control of exchange of heat with the environment
Ectotherms / poikilotherms / cold-blooded
Obtain body heat from the environment
i) Include invertebrates, amphibians, reptiles, and fish
Endotherms / homeotherms / warm- blooded
Generate their own body heat and have a much higher basal metabolic rate (BMR) than ectotherms
Evaporation
A regulatory mechanism. Body heat is removed as liquid evaporates (endergonic process)
Metabolism
A regulatory mechanism. Muscle contraction and other metabolic activities generate heat
Surface area
A regulatory mechanism. Vasodilation or vasoconstriction of extremity vessels results in heat retention or removal
i) Blood flow to ears reduces body temperature, or concurrent exchange keeps central parts of the body warm
External respiration
Entry of air into the lungs and the subsequent gas exchange between alveoli and blood
Internal respiration
Gas exchange between blood cells and intracellular respiration processes.
Invertebrate Respiration - Cnidaria
Protozoa and Hydra.
Direct with environment - have large surface areas and every cell is either exposed to environment or close to it —> simple diffusion of gases directly with outside environment (flatworms; small animals only)
Invertebrate Respiration - Annelids
i. The mucus secreted by earthworms provides a moist surface for gaseous exchange via diffusion
ii. The circulatory system brings oxygen to cells, and waste products back to the skin for excretion
Invertebrate Respiration - Arthropods (80% of all living species; insects, spiders, crustaceans) - Grasshoppers
i. Grasshopper - series of chitin-lined respiratory tubules called trachea that open to the surface via openings called spiracles, through which oxygen enters and carbon dioxide exits
i) No oxygen carrier like hemoglobin is needed due to the direct distribution and removal of respiratory gases between the air and body cells
ii) The moistened tracheal endings ease the rate of diffusion
Invertebrate Respiration - Arthropods (80% of all living species; insects, spiders, crustaceans) - Spiders
ii. Spider - have book lungs
that are stacks of flattened membranes enclosed in internal chambers
Invertebrate Respiration - Fish
When water enters the mouth, it passes over the gills, which are evaginated structures that create a large surface area and take in oxygen and deposit carbon dioxide. Gills can be external/unprotected or internal/ protected, and water exits via the operculum (gill cover)
Countercurrent exchange - exchange between opposing movements of water and underlying blood that maximizes diffusion of oxygen into the blood and carbon dioxide into water
Aerobic respiration - Plants
i. Glucose —> 2 ATP + 2 pyruvic acid
ii. Gases diffuse into the air space by entering and leaving through stomata of leaves or lenticels in woody stems
iii. Anaerobic respiration takes place in simple plants when oxygen is lacking
Right vs left lung
Right lung has 3 lobes. Left lung has 2 lobes that are smaller to accommodate the heart
Pleurae
Membranous cover of the lungs. Two layers: visceral and parietal pleura. Space between the two layers is the intrapleural space
Visceral pleura
Lines the surface of the lungs
Parietal pleura
Lines the inside of the chest cavity
Intrapleural space and inhale/exhale logic
Has negative (lower) pressure relative to the atmosphere. If stabbed, air rushes in and causes the lung to collapse
i. The pressure of this intrapleural space decreases as we inhale: as the diaphragm contracts, the lung cavity opens up, and this increase in volume equates to a decrease in pressure
As we inhale, the volume of lungs expands as the diaphragm drops. Thus, we create a negative pressure relative to the atmosphere, causing air to rush in. The sequence events during an exhale occurs as follows: Diaphragm rises —> volume in lungs decreases —> the pressure inside of the lungs increases relative to the atmosphere —> air rushes out
CO2 and HCO3(-)
CO2 is transported as HCO3(-) (bicarbonate ion) in blood plasma. The conversion is catalyzed by the enzyme carbonic anhydrase via the following reaction:
CO2 + H2O H2CO3 H+ + HCO3(-)
This process occurs in red blood cells (RBCs). Some of the CO2 can also mix directly with the plasma as a gas or can bind with hemoglobin inside of the RBCs, forming carbaminohemoglobin.
Carbaminohemoglobin
CO2 binding with hemoglobin inside the RBCs
Alveoli
Where gas exchange between the circulatory system and lungs occurs. The alveoli are coated with surfactant, a liquid covering that reduces the surface tension, preventing H2O from collapsing the alveoli.
Two types of epithelial cells in human alveoli
Type 1 (structural support) and type 2 (produce surfactant)
Nose
Filters, moistens, and warms incoming air. The mucus secreted by goblet cells traps large dust particles here
Pharynx
Throat, passageway for food and air; dust and mucus are swept back here by cilia for disposal via spitting or swallowing
Larynx
Voice box; if non-gas enters the cough reflex activates
i. Note that the larynx is actually after the epiglottis in terms of sequence
Trachea
Epiglottis covers the trachea
during swallowing; contains C-shaped ringed cartilage covered by ciliated mucus cells
Bronchi / Bronchioles
2 bronchi, which enter the lungs and branch into narrower bronchioles
Alveoli
Each bronchiole branches ends in these small sacs, which are surrounded by blood-carrying capillaries
Diffusion between alveolar chambers and blood
Gas exchange occurs across the moist, sac membranes of alveoli via simple diffusion. O2 diffuses through the alveolar wall, through the pulmonary wall, into the blood, and into RBC. CO2 follows the same sequence, except in reverse. The greater the distance O2 needs to travel, the lower the efficacy of gas exchange
Bulk flow of O2
O2 is transported through the body within hemoglobin containing RBC
Diffusion between blood and cells
O2 diffuses out of RBCs, across capillary walls, into interstitial fluids and
across cell membranes. CO2 does this in reverse
Bulk flow of CO2
CO2 is mainly transported as HCO3(-) ions in plasma, which are produced by carbonic
anhydrase in RBC.
CO2 can also directly mix with plasma as CO2 gas, or bind hemoglobin inside red blood cells.
Bulk flow of air into and out of lungs - Inhalation
Diaphragm and intercostal muscles (between the ribs) contract and flatten. The lungs increase in volume and decrease in pressure, leading to a bulk flow of air into lungs
Bulk flow of air into and out of lungs - Exhalation
Passive process; decrease in lung volume / increase in pressure leads to air rushing out, and the diaphragm relaxing and expanding
Bohr Effect
Refers to the shift in the oxygen dissociation curve caused by changes in the concentration of CO2 or pH.
Hemoglobin O2 binding affinity decreases under conditions of low pH (which results from high CO2 and H+). A decreased binding affinity leads to oxygen being released by hemoglobin. A decrease in CO2 or increase in pH will result in hemoglobin binding more O2.
Bohr effect curve - High CO2
When we have a high concentration of CO2, it diffuses into the blood and into the RBC where carbonic anhydrase converts it into H2CO3. This H2CO3 then becomes HCO3(-) and H+
Hemoglobin now comes into play as it interacts with the H+ to form a more reduced form of hemoglobin that has lower affinity for O2, and greater affinity for CO2, causing O2 to be released.
Bohr effect curve - Low pH
High CO2 and low pH are related. Because low pH means a greater presence of H+ ions, the hemoglobin structure is altered to the reduced form that will release its oxygen.
Bohr effect curve - High temperature
At higher blood temperatures, hemoglobin becomes less likely to bind to oxygen and releases oxygen to tissues
Bohr effect curve - High 2,3-DPG
2,3-DPG (also known as 2,3-BPG) is produced from an intermediate compound in glycolysis and decreases the affinity of hemoglobin for oxygen. At low O2 levels, an enzyme catalyzes the synthesis of 2,3-DPG, hence, high [2,3-DPG] = low affinity of hemoglobin for O2
i. This is helpful for unloading oxygen during anemia or at high altitudes, which in both cases, we are struggling for O2
ii. At high O2 levels, oxyhemoglobin inhibits the enzyme that synthesizes
2,3-DPG, leading to low concentrations of the compound.
CADET, face right
The factors (CO2, Acid, 2,3- DPG, Exercise, and Temperature) that shift the oxygen dissociation curve to the right. A right shift involves physiological states where tissues need more oxygen
Haldane Effect
Describes how the deoxygenation of blood increases its ability to carry CO2. When there is an increase in CO2 pressure, there is an increased CO2 blood concentration. However, when hemoglobin is saturated with oxygen, its capability to hold CO2 is reduced.
Hemoglobin without oxygen acts as a blood buffer by accepting H+ —> this reduced hemoglobin has a higher capacity to form carbaminohemoglobin, rather than the oxygen carrying kind
Haldane Effect relates how [O2] is affecting hemoglobin’s affinity for CO2 and H+, which work in synchrony to facilitate the liberation of O2 and uptake of CO2 and H+.
Bohr and Haldane Effects - 3 interacting equilibrium systems
CO2 + H2O H2CO3 H+ + HCO3(-)
H+ + HbO2 H+Hb + O2
CO2 + HbO2 HbCOO(-) + H+ + O2
Medulla oblongata
Signals the diaphragm to contract, completing the following:
- When partial pressure of CO2 increases, the medulla stimulates an increase in the rate of ventilation
- The diaphragm is signalled to contract. The diaphragm is also the only organ which only and all mammals have, and without which no mammals can live.
- When the lungs inflate, the thoracic pressure decreases as the thoracic cavity size increases
This pattern repeats over and over again, giving us a steady breathing rate.
Methods/forms of CO2 transport in blood
Majority of CO2 in blood is transported in the form of bicarbonate (HCO3(-)). To a lesser extent, CO2 can be transported bound to
hemoglobin/plasma proteins. To an even lesser extent, CO2 is simply dissolved in the plasma. CO2 is significantly more soluble in blood than O2.
Central chemoreceptors
Contained in medulla. Indirectly monitor [H+] in the cerebrospinal fluid
Peripheral chemoreceptors
Contained in heart. Located in carotid arteries and aorta and function to monitor the atrial concentrations of CO2, O2, and pH via H+
Ciliated pseudostratified columnar epithelial cells
Found in trachea and upper respiratory system; may contain goblet cells for mucus production
Emphysema
A pathology marked by destruction of the alveoli
Effects of smoking
Damage to cilia of respiratory cells and allow toxins to remain in the lungs
i. Mucus produced by goblet cells increases, and lungs have a decreased means of moving mucous out, leading to a persistent yet unproductive cough
ii. Can lead to bronchitis emphysema, and lung cancer
Oxyhemoglobin
98% of blood oxygen binds rapidly and reversibly with protein hemoglobin inside of RBC’s, forming oxyhemoglobin
Hemoglobin
Structure has 4 polypeptide subunits, with each subunit hosting a heme cofactor (an organic molecule with an iron atom in the center)
i. Each iron atom can bind with one O2 molecule
ii. Exhibits cooperativity - when one O2 binds, the rest of the O2 molecules can bind easier, hence explaining the
sigmoidal curve graph of hemoglobin binding. The same is true for the opposite: when one O2 is released, the rest are released easier
As O2 pressure increases, O2 saturation of hemoglobin increases
This is ideal: in the lungs we are O2 rich and want to hang onto it, but in the tissues, we are O2 poor (lower O2 pressure) so the hemoglobin will release O2 to tissues
O2 saturation of hemoglobin also depends on CO2 pressure, pH, and temperature of blood
i. The oxygen dissociation curve shows the percentage of hemoglobin bound to O2 at various partial pressures of
O2
ii. Curve is shifted right (O2 released easier) when there is an increase in CO2, decrease in pH, increase in 2,3- DPG, or increase in temperature. CADET, face right!
iii. Bohr Effect - hemoglobin binding affinity decreases under conditions of low pH (high CO2/high H+) which
leads to O2 loads released by hemoglobin since both O2 and H+ compete for hemoglobin binding sites
Chloride shift
Chloride shift occurs to balance bicarbonate entering and leaving the cell. Carbonic anhydrase is in RBCs, so at the tissues to balance bicarbonate diffusing out of the cells, Cl- enters.
Respiratory acidosis
Results from inadequate ventilation; we don’t clear enough CO2 and it builds up, so more H+ is formed, lowering the pH
Respiratory alkalosis
Results from breathing too rapidly (hyperventilation);
we are losing CO2 too quickly, so H+ and HCO3(-) start combining to form more CO2, and the pH begins rising
Myoglobin vs Fetal Hemoglobin Curves
Myoglobin of muscle has a hyperbolic curve since the structure doesn’t participate in allosteric cooperative binding due to the single subunit shape. Myoglobin also saturates quickly and releases in situations of very low oxygen “emergency situations”
Fetal hemoglobin curve is shifted left of the adult hemoglobin curve because the structure has a higher binding affinity in order to grab O2 from maternal blood.
Carboxyhemoglobin
Carbon monoxide (CO) has a 200x greater affinity for hemoglobin than oxygen does [forms carboxyhemoglobin] and requires administration of pure O2 to displace it once bound
Avian respiration
Due to the unique anatomy of birds, respiration is both continuous and unidirectional. Air sacs allow birds to exchange gas during both inhalation and exhalation — oxygen rich incoming air is first stored in air sacs before entering lungs for exhalation, so it is not mixed with the deoxygenated outgoing air.
Mammalian respiration
Tidal breathing. Breathe in and out through the same tubing, inhibiting gas exchange during exhalation. Deoxygenated air is mixed with some fresh air during inhalation, some it is re- breathed. Much less efficient than birds.
Tidal volume (VT)
Volume of air that is normal inhaled or exhaled in one quiet breath
Inspiratory reserve volume (IRV)
Maximum volume of air that can be inhaled after a normal tidal volume inhalation
Expiratory reserve volume (ERV)
Maximum volume of air that can be exhaled after a normal tidal volume exhalation
Residual volume (RV)
Amount of air remaining in the lungs after maximum exhalation; air that cannot be exhaled
Vital capacity (VC)
Maximum volume of air that can be exhaled after a maximum inspiration; expressed as IRV + VT + ERV
Inspiratory capacity (IC)
Volume of air that can be inhaled after a normal exhalation; expressed as VT + IRV
Functional residual capacity (FRC)
Volume of air remaining in the lungs after normal exhalation; expressed as ERV + RV
Total lung capacity (TLC)
Maximum amount of air that the lungs can accommodate; expressed as IC + FRC
Circulation in Invertebrates - Protozoans (unicellular animal-like [due to movement] protists)
Rely on the movement of gas via simple diffusion within the cell
Circulation in Invertebrates - Cnidarians
Body walls are 2 cells thick, so all cells are in direct contact with either internal or external environment
i. Example: hydra
Circulation in Invertebrates - Arthropods (includes most insects and mollusks)
i. Open circulatory systems - pump blood into an internal cavity called the hemocoel (has smaller cavities called sinuses), which bathes tissues in oxygen and nutrient containing fluid called hemolymph
ii. Hemolymph returns to the pumping mechanism (heart) through holes called ostia
Circulation in Invertebrates - Arthropods (includes most insects and mollusks) - Mollusks
Most have open circulatory systems except for cephalopods, which have closed circulatory systems
a. Cephalopods have closed systems due to large oxygen demands, and have gill hearts
Circulation in Invertebrates - Arthropods (includes most insects and mollusks) - Annelids (Include earthworms)
a. Have closed circulatory systems in which blood is confined to vessels (also seen in certain mollusks and vertebrates
Path of circulation in closed system
System Away from heart: aorta —> arteries —>
arterioles —> capillaries
Back to heart: capillaries —> venules —> veins
The dorsal vessel functions as the main heart or pump; aortic loops link the dorsal and ventral vessels together which function in pumping blood
Number of heart chambers in different animals
Human and bird hearts have 4 chambers, reptiles and amphibians have 3 chambers, fish have 2 chambers, and crocodiles and alligators have 4 chambers
Pericardium
A fluid filled sac that surrounds the heart in order to protect and lubricate it for proper function
Right atrium
Chamber where deoxygenated blood enters via the superior and inferior vena cava
Right ventricle
Blood is squeezed into this chamber through the right AV (atrioventricular)/tricuspid valve, which contracts and pumps blood into the pulmonary artery via the pulmonary semilunar valve
i. When the ventricle contracts, the AV valve closes to prevent back flow, which produces the ‘lub’ sound
ii. When the ventricle relaxes, the semilunar valve prevents back flow from pulmonary artery back into ventricles by closing, thus creating the ‘dub’ sound
Pulmonary circuit
The blood pathway from the right side of the heart to the lungs, and eventually to the left side of the heart
Systemic circuit
The circulation pathway through the body between left and right sides of the heart
Left atrium
After traveling through the lungs, oxygenated blood enters the left atrium via the pulmonary veins
Left ventricle
After traveling through the left AV/mitral/bicuspid valve, blood from the left ventricle enters the aorta through the aortic semilunar valve into the rest of the body:
i. Aorta (largest vessel) —> arteries —> arterioles —> capillaries —> tissues get the nutrients they need —> venules —> veins —> superior and inferior vena cava —> the cycle repeats
ii. The left AV valve prevents back flow into the atrium, and the aortic semilunar value prevents back flow into the ventricle
Ejection fraction
The percentage of blood that leaves the ventricles when the heart pumps. Not all blood leaves the ventricles when the heart pumps.
Cardiac Cycle
This cycle is the rate regulated cycle by auto- rhythmic cells of the autonomic nervous system, but contractions are initiated independently of the autonomic nervous system. Instead, the heart contracts automatically:
- SA (sinoatrial) node / pacemaker
- AV node
- Ventricular contraction
SA (sinoatrial) node / pacemaker
Part of cardiac cycle.
Located in upper wall of the right atrium, the SA node is a group of specialized cardiac muscle cells that initiate by contracting both atria and sending an impulse that stimulates the AV node.
i. At the AV node, the impulse is briefly delayed to allow the atria to completely empty, and to allow the ventricles to fill with blood.
ii. The impulse spreads the contraction to surrounding cardiac muscles via electrical synapses made from gap junctions
iii. The pace of the SA node is faster than the normal heartbeat, but the parasympathetic vagus nerve innervates the SA node and slows contractions
a. The vagus nerve also increases digestive activity of intestines
AV node
Part of cardiac cycle.
Located in the lower wall of the right atrium / interatrial septa; sends impulse through the Bundle of His —> passes between both ventricles —> branches into ventricles via the purkinje fibers which results in contraction of both ventricles simultaneously
Ventricular contraction
Part of cardiac cycle.
When the ventricles contract (ventricular systole phase), blood is forced through the pulmonary arteries and aorta.
Papillary muscles and chordae tendinae
Papillary muscles and chordae tendinae are attached to cardiac valves and force them closed during systole
Ventricles vs atria
Ventricles have thicker walls than atria and generate higher blood pressure because ventricles must pump blood throughout the body and lungs, while atria only need to generate enough pressure to fill the ventricles.
Left vs right ventricle
Left ventricle is thicker than the right because the left ventricle pumps blood to most of the body, but the right ventricle only pumps to the lungs
Systole
Occurs when the atria or ventricles contract
Diastole
Occurs during relaxation of atria or ventricles
Semilunar valves
Aortic and pulmonary valves
Atrioventricular valves
Tricuspid/right AV valves and bicuspid/left AV/mitral
Blood pressure
Hydrostatic pressure from the heart contracting causes blood to move through the arteries. Blood pressure drops as it reaches the capillaries, and reaches near zero in the venules
Blood moves through the veins due to
- Pumping of the heart assisted by movements of adjacent skeletal muscles
- Expansion of atria each time the heart beats
- Falling pressure in the chest when a person breathes
Valves in the veins
Prevent back flow
Closed circulatory system
Blood is transported via arteries, veins, and capillaries
Open circulatory system
Soaking the organs in a bath of blood
Arteries
Thick-walled, muscular, elastic vessels that pump oxygenated blood away (except for pulmonary arteries that transport deoxygenated blood from the heart to lungs). Wrapped in smooth muscle, arteries are typically innervated by the sympathetic nervous system.
Large vs medium-sized arteries
Large arteries have less smooth muscle (per volume) than medium sized ones; larger arteries are also less affected by the sympathetic nervous system, but medium sized arteries can constrict enough to re-route blood.
Layers of arteries
Arteries have three layers (tunics)
a. Endothelial lining (inner)
b. Smooth muscle and elastic tissue (middle)
c. Connective tissues (outer)
Arterioles
Very small vessels wrapped in smooth muscle, and constrict or dilate to regulate blood pressure or re-route blood. Are a major determinant of blood pressure as they have the greater resistance to blood flow
Capillaries
Have the smallest diameter and have a single layer of endothelial cells across which gases, nutrients, enzymes, hormones, and waste diffuse
Methods for materials to cross capillary wall
a. Endo or exocytosis (proteins)
b. Diffusion through capillary cell membrane (O2 and CO2)
c. Movement through pores called fenestrations
d. Movement through space
between the cells (ions)
Pericytes
Sometimes you will see pericytes (contractile cells) around the capillaries and venules throughout the body
Capillary exchange
Capillaries exchange with the interstitial fluid that surrounds tissue cells.
Blood hydrostatic pressure
The pressure from the flow of blood pushing outward
Blood colloid osmotic pressure
Osmotic pressure exerted by blood proteins, usually in the plasma, and wants to pull water into the capillary (oncotic pressure)
Net filtration and net absorption
Blood flowing in from the capillaries has a high blood hydrostatic pressure — so high that it overcomes the blood colloid osmotic pressure working against it.
Net filtration at the capillary end of the bed is, therefore, fluid moving outward. But, towards the end of the capillary bed, blood hydrostatic pressure has decreased enough that blood colloid osmotic pressure overcomes it, and fluid flows back inward (net reabsorption) at the venous end
Pre-capillary sphincters
Regulate the passage of blood into capillary beds
Venules
Small blood vessels that lead back to veins and are very thin and porous
i. Drain blood from capillary bed —> venules combine —> veins
Veins
Larger veins often have valves to aid in the transport of deoxygenated blood back to the heart due to fighting gravity (except for pulmonary veins and umbilical veins that carry oxygenated blood)
Cross sectional areas
The cross-sectional area of veins is about 4x higher than that of arteries, and the total cross-sectional area of capillaries is far greater than that of arteries of veins. While capillaries are the narrowest vessels, there are far more capillaries
Blood velocity
Because blood volume flow rate is approximately constant, blood velocity is inversely proportional to total cross-sectional area. Blood pressure drops as we go from aorta —> capillaries because of energy loss due to increased resistance and decreased vessel diameter.
Blood pressure equation
Blood pressure = cardiac output * systemic vascular resistance (resistance controlled by vasoconstriction/dilation). If resistance increases, why does pressure decrease?
The blood pressure formula above applies to MAP (mean arterial pressure}, which is measured at the arteries by a sphygmomanometer. When a blood vessel constricts (increased resistance), the blood pressure is indeed higher in the part of the tube before the constriction (which is presumably where we measure blood pressure).
The pressure after the constriction is what is lowered, hence why blood pressure effectively decreases as we go through smaller diameter vessels. By the time we hit venules/veins, the original source of the blood pressure/flow (the beating of the heart) is virtually gone, which is why the pressure continues to decrease further.
Vessel with greatest resistance to flow (highest ability to constrict)
Arterioles
Location of most blood
At any given time, most blood is in the veins/venules/venus sinuses
Lymphatic system
An open secondary circulatory system that transports excess interstitial fluids (lymph) through the contraction of adjacent muscles, and some walls of larger lymph vessels have smooth muscle
Lymphatic system - Proteins and large particles
Proteins and large particles that can’t be taken up by the capillaries are removed to the lymph, which also monitors blood for infection. Also transports absorbed fat from small intestine to the blood
Lymphatic system - Valves
Has valves to prevent back flow - fluid returns to the blood circulatory system through two ducts located in the shoulder region (thoracic duct and right lymphatic duct) which empty into the left and right subclavian vein, respectively. This fluid eventually rejoins the blood as plasma.
Lymphatic system - Nodes
Contains lymph nodes - these cotton phagocytic cells (leukocytes) that filter the lymph and serve as immune response centers. Swollen glands during sickness are actually lymph nodes filled with white blood cells!
Lymphatic system - Organs
The thymus and bone marrow are the primary central lymphoid organs that can replenish immune cells (T-Cells in thymus, B-cells in bone marrow).
i. The lymph nodes, spleen, adenoids, appendix, Peyer’s patches (found in small intestine), and tonsils are peripheral lymphoid tissues [TALAPS]
a. These house immune system cells but can’t replenish them
b. The thymus technically doesn’t make new T-cells, but T-cells mature there so it houses fresh ones
Blood
There are 4-6 liters in the human body, and is a connective tissue. The heart pumps ~7000 L of blood a day
Percentage components of blood
55% liquid (plasma) and 45% cellular components.
Plasma, blood serum, RBC, leukocytes (WBC), platelets/thrombocytes
Plasma
Component of blood.
Aqueous mixture of nutrients, salts, gases, wastes, hormones, and blood proteins (immunoglobulins, albumin, fibrinogen, clotting factors)
Blood serum
Component of blood.
The same as plasma minus any clotting factor components
Erythrocytes (RBCs)
Component of blood.
a. Transports oxygen on
hemoglobin
b. Catalyzes conversion of CO2 and H2O to H2CO3
c. Lacks a nucleus and organelles to maximize hemoglobin content
d. Do not undergo mitosis
e. Contain spectrin, which enables them to resist strong shearing forces
f. If the tissues do not receive enough oxygen, the kidneys can synthesize and secrete a hormone called erythropoietin (EPO) to stimulate generation of more erythrocytes in bone marrow
g. Derive energy from glycolysis
Leukocytes (WBCs)
Component of blood.
Are larger than RBCs and phagocytize foreign matter and organisms
a. Contain organelles but no
hemoglobin
b. Undergo diapedesis - a process by which WBCs become part of the interstitial fluid and slip through the endothelial lining
Platelets/thrombocytes
Component of blood.
Cell fragments involved in blood clotting
a. Lack nuclei and stick to damaged epithelium in order to attract more platelets
b. Convert fibrinogen (inactive) to fibrin (active)
c. Are formed from small portions of membrane-bound cytoplasm torn
from megakaryocytes
d. Can produce prostaglandins and some important enzymes
Process of Blood Clotting
- Formation of platelet plug
- Release of thromboplastin
- Conversion of prothrombin to thrombin
- Conversion of fibrinogen to fibrin
- Clot formation
First step of blood clotting
Formation of platelet plug - platelets contact exposed collagen of damaged vessel and cause neighboring platelets to form a platelet plug
Second step of blood clotting
Release of thromboplastin - both the platelets and damaged tissue release the clotting factor thromboplastin
Third step of blood clotting
Conversion of prothrombin to thrombin - thromboplastin converts inactive plasma protein prothrombin to thrombin (active)
Fourth step of blood clotting
Conversion of fibrinogen to fibrin - thrombin converts fibrinogen into fibrin
Fifth step of blood clotting
Clot formation - fibrin threads coat the damaged area and trap blood cells to form a clot
Thrombus
A thrombus (blood clot that forms in a vessel abnormally) can cause a heart attack or stroke (if the clot causes death of nervous tissue in the brain)
Fetal circulation
Occurs both inside of the mother and her fetus that essentially temporarily re-wires the cardiovascular systems.
The process occurs as follows: Oxygenated, nutrient-rich blood from placenta carried to fetus via umbilical vein —> half of the blood enters the ductus venosus, which allows blood to bypass the liver —> blood is carried to the inferior vena cava —> right atrium —> right ventricle —> ductus arteriosus (conducts some blood from the pulmonary artery to the aorta [bypassing the lungs/fetal pulmonary circulation]) —> aorta
The other half of the blood that didn’t enter the ductus venosus enters the live/portal vein —> right atrium —> foramen ovale (a small opening in the heart which allows blood to bypass pulmonary circulation by entering the left atrium directly from the right atrium since there is no gas exchange in the fetal lung) —> left atrium — > left ventricle —> aorta
Baby’s first breath
CO2 stimulates a baby’s first breath as receptors in the nose detect it and acts as a respiratory stimulant. The temperature change from leaving the womb also stimulates the first breath. Surfactant is especially important here because the first breath is difficult — newborn lungs are collapsed and the airways are small, leading to lots of resistance to air movement.
Cardiac output (CO) equation
Cardiac output (CO) = stroke volume (SV) x heart rate (HR)
Stroke volume
Volume of blood discharged from the ventricles with each contraction
Cardiac output
Volume discharged from the ventricle each minute
Stroke volume equation
Stroke volume = end diastolic volume (EDV) - end systolic volume (ESV)
End diastolic volume (EDV)
Volume of blood in the ventricle just before contraction
End systolic volume (ESV)
Blood in the ventricle at the
end of the contraction/systole
Mean atrial pressure (MAP) equation
Blood pressure (BP) / Mean atrial pressure (MAP) = CO x Systemic Vascular Resistance (SVR)
Systemic Vascular Resistance (SVR)
Resistance controlled by
vasoconstriction/dilation — the larger the diameter, the less resistance
Rh factor; Erythroblastosis fetalis
Another blood antigen; a mother might attack Rh+ antigens in her second fetus, which is a condition known as erythroblastosis fetalis. This condition is also known as Rh incompatibility. The first child that is Rh+ while the mother is Rh- is fine, but during the first childbirth, the blood exposure leads to antibodies that attack the Rh+ fetus during the second childbirth, and can be fatal
Double capillary beds (portal systems)
Occur in the hepatic portal system (stomach/intestines/spleen drain via the hepatic portal vein to capillaries of the liver), and the hypophyseal portal system between the hypothalamus and anterior pituitary gland. Non-mammals also possess a renal portal system.
Movement across capillary beds occurs as follows: Capillary bed pools into another capillary bed (1) —> drains into portal vein —> capillary bed (2) —> drains into vein that returns blood to the heart without first going to the heart (which is beneficial since products are transported in a high concentration to a targeted part of the body without spreading to the entire body. For example, the liver can screen for harmful substances picked up from digestion before the heart pumps these substances everywhere)
Phosphate buffer system
Maintains pH of internal fluids of all cells; H2PO4(-) and HPO4(2-) act as acid and base (amphoteric), and bicarbonate acts as an extracellular buffer!
Hemorrhage (excessive bleeding)
Results in a decrease in arterial pressure which is sensed by arterial baroreceptors. The body wants to compensate for this reduced blood pressure, and does so by increasing the heart rate and system vascular resistance.
i. This makes sense logically: blood pressure has fallen —> the body wants to raise it —> cardiac output and heart rate increase —> this increases stroke volume and system vascular resistance
Blood-brain barrier (BBB)
The blockade of cells that prevents or slows the passage of drugs, ions, and pathogens into the central nervous system. This is permeable to O2, CO2, glucose, and general anesthetics
Osmoregulation
Maintenance of osmotic pressure of fluids by control of water and salt concentrations
Osmoregulation - Marine fish
This body is hypotonic to the environment —> water is constantly lost by osmosis, so these fish are constantly drinking water, rarely urinating, and secreting accumulated salts through gills
Osmoregulation - Fresh water fish
Body is hypertonic to the environment —> water moves in, so the fish are rarely drinking water, constantly urinating, and absorbing salt though gills
Invertebrate Excretion - Protozoans and Cnidarians
All cells are in contact with external, aqueous environment.
i. Have water soluble wastes (ammonia, CO2) that exit via simple diffusion
ii. Protists such as paramecium and amoebas possess contractile vacuoles for excess H2O excretion via active transport
Invertebrate Excretion - Annelids
Excrete CO2 directly through moist skin
Invertebrate Excretion - Annelids - Nephridia (metanephridia)
Functional unit of excretion that occur in pairs within each segment of annelids (earthworms).
a. Interstitial fluids enter a
nephridium through a ciliated opening called a nephrostome and concentrate through a collecting tubule due to selective secretion into surrounding coelomic fluid. Blood that surrounds the tubule reabsorbs the fluid. Water, salts, and urea are excreted through an excretory pore.
Invertebrate Excretion - Platyhelminthes
Possess flame cells/ flame bulbs, which are bundles of flame cells that combine to form protonephridia, that are distributed along a branched tube system that permeates the flatworm
i. Body fluids are filtered across flame cells, whose cilia move fluids through the tube system; wastes exit through pores of the tube (these are also found in Rotifera)
Invertebrate Excretion - Arthropods
CO2 is released from tissue via trachea, which lead to the external air via spiracles
Invertebrate Excretion - Arthropods - Malpighian tubules
Found in arthropods (terrestrial insects) and are tubules that attach to the mid digestive tract (midgut) and collect body fluids from the hemolymph that bathes the cells. The fluids are deposited into the midgut
a. Fluids include nitrogenous wastes including uric acid crystals (formed from water and retained salts). As fluids pass through the hind-gut, retained materials pass out of walls and wastes continue down the tract for excretion through the anus
b. Aquatic crustaceans use green glands instead, which function similar to malpighian tubules
Nitrogenous waste
Nitrogenous waste is usually converted to ammonia, which is also toxic. Excretion handling is varied depending on the organism.
Excretion in Humans - Lungs
CO2 and H2O (gas) diffuse from the blood and are continually exhaled
Excretion in Humans - Liver
Largest internal organ that processes nitrogenous wastes, blood pigment wastes, other chemicals, produces urea via the urea cycle
Excretion in Humans - Skin
Sweat glands in the skin excrete water and dissolved salts to regulate body temperature
i. Is the largest organ overall
ii. Sweat gland function decreases as we age
Excretion in Humans - Kidney regions
i. The outer cortex
ii. Inner medulla
iii. Renal pelvis which drains to the ureter
Nephrons
Each kidney has many nephrons, the functional unit of the kidney. Composed of a renal corpuscle and renal tubule, and function to reabsorb nutrients, salts, and water
Kidney functions
i. Excrete waste via the path - kidneys —> ureter —> bladder —> urethra
ii. Maintain homeostasis of body fluid volume and solute composition
iii. Regulate blood pressure
Renal corpuscle
Contains the glomerulus, which acts as a sieve, and Bowman’s capsule, which encloses the glomerulus. Bowman’s capsule also contains two arterioles: an afferent arteriole that leads into the glomerulus, and an efferent arteriole that leads out of the glomerulus
Hydrostatic pressure in renal corpuscle
Hydrostatic pressure forces plasma through the fenestrations (small pores) of the glomerular endothelium, and into Bowman’s capsule. These fenestrations screen out blood cells and large proteins from entering Bowman’s capsule
a. The fluid that does get in is called the filtrate/primary urine.
b. Podocytes are cells in Bowman’s capsule that filter blood and hold back large molecules (proteins) and allow smaller molecules (sugars, water, salts) through
Efferent arteriole
After the efferent arteriole passes back out of the glomerulus, it webs around the entire nephron structure as the peritubular capillaries (which surround the proximal convoluted tubule and distal convoluted tubule and reabsorb materials) and vasa recta (which surrounds the Loop of Henle in the kidney’s medulla and maintains the concentration gradient) before dumping back into the renal branch of the renal vein
Renal tubule
Contains Proximal convoluted tubule (PCT), Loop of Henle, Distal convoluted tubule
(DCT), Collecting duct
Proximal convoluted tubule (PCT)
Where active reabsorption of almost all glucose, amino acids, and some NaCl, as well as passive reabsorption of K+ and HCO3- begins. Water follows these ions out so the cortex is not salty. Most reabsorption takes place here
a. Drugs, toxins, NH3 also get secreted into the filtrate; H+ ions are secreted in as well as via anti- port with Na+
b. The net result of the PCT is to reduce the amount of filtrate, but the concentration stays roughly the same
c. PCT cells have a lot of mitochondria due to all of the active reabsorption that takes place here
Loop of Henle
Makes up a majority of the nephron
Descending loop of Henle
Is only permeable to water (but this water is picked up by the vasa recta so the medulla stays salty) via lots of aquaporins. The solute concentration in the tube increases as a result
Ascending loop of Henle
Makes the renal medulla salty: first passively and then actively by pumping out NaCl. The ascending loop is also impermeable to water! Solute concentration in the tube decreases as a result.
Distal convoluted tubule
DCT
More reabsorption of glucose, ions and water occurs here so the cortex isn’t salty. The filtrate (NaCl and HCO3-) get actively pulled out and reabsorbed into the body, and K+/H+ are actively secreted into the tubule. Some water passively gets pulled out, but overall, the filtrate concentration is lowered.
Aldosterone, and to a lesser extent ADH, can act on the end of the distal tubule to increase its permeability to water, which is normally not permeable. Aldosterone increases the amount of Na+/K+ antiport — more K+ gets secreted into the tubule as more Na+ is resorbed from the tubule. Water follows the Na+ out and the concentration of the filtrate increases.
Collecting duct
Collects the remaining filtrate. What happens here (concentrated or dilute urine) is highly dependent on what hormones are acting on it.
a. We can have resorption of NaCl at the upper part of the medulla, and the collecting duct is largely impermeable to water unless ADH acts on it. The body uses ADH to control how much water we retain.
b. Urea is also resorbed here which maintains the medulla’s osmolarity (although sometimes it can re- enter the tubule at the Loop of Henle — a phenomenon known as urea recycling)
Path of urea through collecting duct
- Urea first descends to the medulla (salty part) where antidiuretic hormones (ADH/vasopressin) can make more water leave from urine by increasing permeability of the collecting duct (via increased aquaporins) —> urine is even more concentrated. Note that one collecting duct is shared by many nephrons.
- Aldosterone can also act on the collecting duct by increasing Na+ reabsorption, resulting in water passively following Na+
- By the time urine emerges, it usually has varying amounts of: H2O, urea, NaCl, K+, and creatinine
Alcohol
Alcohol blocks the creation of vasopressin and leads to more urine output since less H2O is resorbed by the body!
Urine formation
Filtration, reabsorption, secretion, and concentration
Filtration
The fluid that goes through the glomerulus (afferent arteriole —> glomerulus —> efferent arteriole) to the rest of the nephron is called filtrate, which is pushed into Bowman’s capsule. Particles that are too large to filter through the glomerulus (such as blood cells or albumin) remain in the circulatory system. This is a passive process that is driven by the hydrostatic pressure of blood.
Reabsorption
Glucose, salts, and amino acids are reabsorbed from filtrate and return to the blood. This process takes place primarily in the PCT via active transport.
The only passive transport here is the movement of water and the leaving of bicarbonate
At the DCT, NaCl and bicarbonate are actively reabsorbed, allowing water to passively follow
To reabsorb something means to bring it back into the blood
Secretion
Substances such as acids, bases, ammonia, drugs, and ions are secreted by both passive and active transport from the peritubular capillaries and into the nephron.
To secrete is to remove a substance from the blood
Concentration
When we’re dehydrated, the volume of fluid in the bloodstream is low, so we need to make small amounts of concentrated urine (and increase our blood fluids).
ADH prevents water loss by making the collecting duct more permeable to water. When blood pressure is low, aldosterone increases reabsorption of Na+ by the DCT and collecting duct, which increases water retention
Excretion equation
Excretion = Filtration - Reabsorption + Secretion
Excretion Recap
- Filtration occurs in the renal corpuscle
- Reabsorption/secretion occurs mostly in the PCT
- Filtrate becomes more concentrated as it moves down the Loop of Henle (passive movement of water out of the tube)
- Filtrate becomes more dilute as it moves up the up (passive and active transport of salts out of the Loop, but no movement of water)
- DCT dumps into the collecting duct
- Filtrate becomes more concentrated again as it descends the collecting duct because the surrounding medulla is salty, causing water to leave
- The collecting duct leads to the multiple renal calyces (singular: renal calyx)
- The renal calyx empties into the renal pelvis
- Drains to ureter
- Drains to urinary bladder
- Urethra
Juxtaglomerular Apparatus
The macula densa, an area of closely packed specialized cells lining the DCT, monitor the filtrate pressure in the DCT. If the blood pressure is low, then via the granular cells —> secrete renin —> angiotensin cascade —> tells adrenal cortex to synthesize aldosterone —> more water is reabsorbed from the DCT and the blood pressure rises and is restored to normal
Selective permeability of the tubules establishes an osmolarity gradient in the surrounding interstitial fluid. Urine is hypertonic to the blood and contains a high urea and solute concentration.
Osmolarity Gradient
Created by the entering and exiting of solutes, and increases from the cortex to the medulla
Counter Current Multiplier
Because the descending loop is permeable to water and the ascending loop is permeable to salts and ions, the medulla is very salty and facilitates water reabsorption.
The innervations of the sympathetic nervous system primarily affects the afferent arterioles (constrict it —> reduces urine output)
Amount of fluid filtered, reclaimed and excreted per day by humans
Humans filter and reclaim a lot of fluid from the bloodstream through the kidney each day (~180 liters!) and 1-2 L are excreted per day
Nitrogen
Waste product
Nitrogenous Waste Products - Aquatic animals
Excrete NH3 and NH4 directly into the water
Nitrogenous Waste Products - Mammals, sharks, and amphibians
Convert NH3 into urea
Nitrogenous Waste Products - Birds, insects, reptiles
Secrete uric acid (is insoluble in water and is excreted as a solid to conserve water)
Allantois
A special sac in bird eggs that keeps nitrogenous waste in the form of uric acid away from the embryo
Excretion in Plants
Excess CO2, waste O2, and H2O (gas) leave via diffusion through the stomata and lenticels via transpiration (recall: woody stems have lenticels)
4 main feeding mechanisms of animals
Filter feeding, substrate feeding, fluid feeding, and bulk feeding
Intracellular digestion
Takes place within the cells and occurs in amoeba, paramecium, and porifera. Food is usually phagocytized, and fuses with food vacuoles and lysosomes to break down nutrients
Extracellular digestion
Takes place outside the cells usually in a food compartment continuous with the animal’s body
Platyhelminthes and Cnidaria digestion
Platyhelminthes and Cnidaria, which have two-way gastrovascular cavities rather than one-way canals, use a combination of extracellular (enzymes secreted into gastrovascular cavity, food particles broken down) and intracellular (food particles engulfed and digested in food vacuoles) digestion.
Digestion in unicellular organisms - Amoeba
Food capture via phagocytosis —> food vacuoles —> fuse with lysosomes
Digestion in unicellular organisms - Paramecium
Cilia sweep food into the cytopharynx. Food vacuoles form and move toward the anterior end of the cell
Invertebrate Digestion
Rely on either physical breakdown, which occurs via cutting and grinding in the mouth and churning in the digestive tract, and/or chemical breakdown, which involves enzymatic hydrolysis —> smaller nutrients —> pass through semi-permeable membrane of gut cells to be further metabolized.
Invertebrate Digestion - Cnidarians
Hydra rely on intracellular and extracellular digestion
Invertebrate Digestion - Annelids
Earthworms have a one-way digestive tract
i. Crop - food storage
ii. Gizzard - grind food
iii. Intestine - contains typhlosole to increase surface area for absorption
Invertebrate Digestion - Arthropods
Have jaws for chewing and salivary glands
Invertebrate Digestion -
Molluscs
Have radula, and tongue/ tooth structure that located in the mouth and breaks down food
4 groups of molecules encountered in digestive system in humans
- Starches —> glucose
- Proteins —> amino acids
- Fats —> fatty acids
- Nucleic acids —> nucleotides
Mouth
Salivary amylase breaks down starch into maltose by breaking starch’s alpha-glycosidic bonds. Chewing creates a bolus which is swelled, and also increases the surface area of food, thus exposing it to more enzymes
Pharynx (throat)
Area where food and air passages cross; epiglottis, a flap of tissue that blocks the trachea so only solid and liquid enter, is located here
Esophagus
Tube leading to stomach, food travels by contractions (wave motion peristalsis via smooth muscle), and saliva lubricates this
Stomach
Secretes gastric juice (digestive enzymes and HCl) and food enters the stomach through the lower esophageal/cardiac sphincter. The stomach contains exocrine glands (local secretion by way of duct) within gastric pits (indentation in stomach that denote entrance to the gastric glands) which contain secreting chief cells, parietal cells, G cells, and mucous cells (secrete mucus to prevent backwash)
Stomach - Storage
Stomach contains accordion-like folds that allow 2-4 liters of storage
Stomach - Mixing
Mixes food with H2O and gastric juice, forming chyme, a creamy medium
Stomach - Physical breakdown
Muscles are activated to break down food; HCl denatures proteins and kills bacteria
Stomach - Chemical breakdown
Pepsin (secreted by chief cells) digests proteins; pepsinogen —> pepsin activated by HCl, which is secreted by parietal cells
Stomach - Peptic ulcers
Caused by failure of mucosal lining to protect stomach. Ulcers can also be caused by excess stomach acid or H. Pylori, which can be treated with antibiotics.
Stomach - Controlled release
Chyme enters the small intestine via the pyloric sphincter
Stomach - Mucous cells
A type of stomach cell.
Secretes mucus that lubricates and protects stomach’s epithelial lining from acid environment. Mucus is mainly composed of sticky glycoproteins and electrolytes, and some cells also secrete a small amount of pepsinogen.
Stomach - Chief cells
A type of stomach cell.
Secrete pepsinogen (zymogen precursor to pepsin). Pepsinogen is activated to pepsin by the low pH in stomach, and once active, it begins protein digestion
Stomach - Parietal cells
A type of stomach cell.
Secrete HCl; intrinsic factor that assists ileum’s B-12 absorption. Possess many mitochondria for energy to establish proton gradient
Stomach - G cells
A type of stomach cell.
Secrete gastrin, a large peptide hormone which is absorbed into blood and stimulates parietal cell to secrete HCl
Stomach - ECL cells
A type of stomach cell.
Neuroendocrine cells in the digestive tract; gastrin stimulates them to release histamine which in turn stimulates parietal cells to produce gastric acid
Stomach cells in general
All cell types are affected by acetylcholine, which increases secretion of each cell. Gastrin and histamine also increase HCl secretion
Stomach pH
A full stomach has a pH of 2, which is extremely acidic and beneficial for killing ingested bacteria, and is the optimal pH for pepsin!
Stomach - Rugal folds
Stomach contains these folds / rippled areas to increase the surface area of the stomach lumen
Absorption in the stomach
Protein digestion begins in the stomach, but no absorption occurs in the stomach
Small Intestine
Food goes from the stomach to the small intestine through the pyloric sphincter. The small intestine has 3 portions: the duodenum, jejunum, and the ileum.
Duodenum
Continues breakdown of starches and proteins as well as remaining food types (fats and nucleotides)
Majority of digestion occurs in duodenum
Jejunum
Absorption of nutrients.
Majority of absorption occurs in jejunum
Ileum
Absorption of nutrients, longest portion and contains Peyer’s patches, which are large aggregates of lymphoid tissue
Amount of digestion and absorption in small intestine
90% of digestion and absorption occurs in the small intestine
Ileocecal valve
Small intestine is connected to the large intestine via the ileocecal valve
Structure of small intestine
Wall has finger-like projections called villi that increase the surface area to allow for greater digestion and absorption. Each villi has a lacteal, a lymph vessel surrounded by a capillary network that functions for nutrient absorption. Villi have microvilli, allowing for greater surface area.
Globet Cells
Goblet cells are found in small intestine and secrete mucus to lubricate and protect from mechanical or chemical damage
pH of duodenum
Duodenum has a pH of ~6 mainly due to bicarbonate ions secreted by pancreas.
Small intestine - Enzyme origin
Proteolytic enzymes like proteases, disaccharadidases, lipases, nucleotidades, phosphatases, and nucleosidases
Pancreas
Secretes bicarbonate and acts as an exocrine gland releasing major enzymes from acinar cells via pancreatic duct —> duodenum
Key enzymes of pancreas
The key enzymes of the pancreas include trypsin, chymotrypsin, lipase, pancreatic amylase, and deoxy/ribonucleases.
These enzymes exist as zymogens/ proenzymes (inactive)
Pancreas - Trypsin
Trypsin gets activated by enterokinases (produced by cells of the duodenum) located in the brush border, then activated trypsin activates the other enzymes
Pancreatic juice
Activated enzymes are secreted into the pancreatic juice, an alkaline solution due to the bicarbonate secreted by the pancreas
Pancreas - Enzyme flow
Enzymes flow from the pancreatic duct —> duodenum and the alkaline fluid helps neutralize the acidic chyme in the stomach, providing a better environment to activate pancreatic enzymes
Liver
Produces bile
The liver’s bile and pancreatic digestive enzymes all come together with food in the duodenum; opening is the sphincter of oddi
Bile
Contains no enzymes but emulsifies fats and contains sodium bicarbonate that helps neutralize stomach acid
Storage and flow of bile
Bile is stored in the gall bladder, and will flow out via the cystic duct (which merges with the hepatic duct of the liver) into the common bile duct, which then merges with the pancreatic duct that secretes into the duodenum (biliary flow). Not all bile is stored in the gall bladder, though, as some flows directly out to the duodenum.
Intestinal fluid
Intestinal fluid is aqueous, which causes fat to clump up. Emulsification (due to bile) breaks up the fat into small particles (without chemically modifying it) which exposes a greater surface area for lipase to work on.
Absorption of breakdown products in small intestine
Remainder of small intestine (6m) absorbs breakdown products (villi and microvilli) i. Amino acids and sugars —> capillaries ii. Fatty acids and glycerol —> lymphatic system —> bloodstream
Chyme in intestines
Chyme moves through intestines via peristalsis - segmentation of the small intestine mixes chyme with digestive juices
Large Intestine (colon)
Where water and salts are reabsorbed to form feces; is 1.5 m long, and has four parts: ascending, transverse, descending, and sigmoid.
Major functions are water and electrolyte absorption
Feces storage
Feces stored at the end of large intestine in the rectum —> excreted through the anus.
Diarrhea
Malfunction of large intestine often leads to diarrhea
Healthy feces breakdown
75% water and solid mass containing 30% dead cells, 10-20% fat, 10-20% organic matter, 2-3% protein, 30% roughage (cellulose), and undigested matter (sloughed cells)
Beginning of large intestine
The beginning of the large intestine is the cecum (before the ascending colon), it has an offshoot of unknown function known as the appendix
Large cecum in herbivores
In herbivores, the large cecum functions in cellulose digestion with the help of bacteria
Bacteria (like E. Coli) a symbiont in large intestine
Main source of vitamin K (also produce Vitamin B12, thiamin, riboflavin)
Gastrin
Hormone produced by stomach lining when food reaches or upon sensing of food
Secretin
Local peptide hormone from SI, produced by cells lining duodenum in response to HCl; stimulates pancreas to produce bicarbonate (neutralizes the chyme)
Cholecystokinin
Hormone secreted by small intestine in response to fat digestates; stimulates gallbladder to release bile and pancreas to release its enzymes. Also decreases motility of stomach —> more time for duodenum to digest fat
Gastric Inhibitory Peptide
Hormone produced in response to fat/protein digestates in duodenum; effect = mild decrease of stomach motor activity
Enterogastrone
Enterogastrone is any hormone secreted by the duodenum in response to lipids that inhibits forward movement of chyme. Includes secretin, CCK, GIP, etc. Inhibits peristalsis and acid secretion by the stomach.
Grehlin
Hormone secreted from stomach wall, initiates hunger
Leptin
Hormone secreted from adipose tissue, inhibits hunger
Peptide YY
Hormone secreted from small intestine and is concerned with hunger and lack of hunger
Insulin
Hormone secreted from pancreas, encourages storage of glucose as glycogen in the liver
Epinephrine
Hormone that suppresses hunger
Digestion in Plants and Fungi
Plants have no digestive system, but intracellular processes similar to animals do occur.
Digestion in Plants and Fungi - Intracellular digestion
Store primarily starch in seeds, stems, and roots; when nutrients are required, polymers are broken down (into glucose, fatty acid, glycerol, and amino acids) by enzymatic hydrolysis
Digestion in Plants and Fungi - Extracellular digestion - Fungi (rhizoids of bread molds)
Secrete enzymes into bread, producing simple digestive products which are then absorbed by diffusion into rhizoid
Digestion in Plants and Fungi - Extracellular digestion - Venus flytrap
Enzymes digest trapped fly (serves as nitrate source) still autotrophic though
Liver functions
The liver receives blood from capillary beds of intestines, stomach, spleen, and pancreas via hepatic portal vein —> liver “works on” this blood. The liver is oxygenated by a second blood supply (via hepatic artery). All blood received from liver —> flattened hepatic sinusoids —> hepatic vein —> vena cava.
The liver functions are: Blood storage, blood filtration, carbohydrate metabolism, fat metabolism, protein metabolism, detoxification, erythrocyte destruction, vitamin storage, glycogenesis and glycogenolysis, mobilizes fat or protein for energy, digestive function
All carbohydrates absorbed into the blood are carried by the portal vein to the liver
