Biology-Animal Form and Function Flashcards
(100 cards)
1
Q
tissues
A
groups of similar cells that perform a common function
2
Q
What are the 4 types of tissues?
A
Connective tissue [bone, cartilage, blood]
Epithelial tissue [skin, internal covering]
Nervous tissue
Muscle tissue
3
Q
organ
A
group of different tissues functioning together to perform a particular activity
4
Q
organ system
A
two or more organs working together to accomplish a certain task. ex. the digestive system
5
Q
homeostasis
A
maintenance of internal conditions within narrow limits; stable conditions usually maintained by neg. feedback
6
Q
negative feedback
A
- receptor senses a change beyond normal limits.
- A control center (often brain) evaluates the change and activates a second mechanism (an effector) to correct the condition
- Once the original condition is negated so that they return to normal, the control center’s corrective action is discontinued
7
Q
positive feedback
A
action intensifies a condition so that it is driven further beyond normal limits (labor contraction, lactation, and sexual orgasm)
8
Q
ectotherms (also called poikilotherms)
A
animals that obtain body heat from their environment so their temperatures often vary w/ the environment’s temperature. ex. invertebrates, amphibians, reptiles, and fish
9
Q
endotherms (homeotherms- since they maintain a constant internal temp.)
A
animals that generate their own body heat
10
Q
How do animals regulate their body temperatures?
A
- Evaporation- liquid to gas (endergonic), body heat removed when water vaporizes
- Metabolism- muscle contraction and other generate heat. (Shivering)
- Surface area- vasodilation/ vasoconstriction (increasing/decreasing diameter of blood vessels) of extremities (arms, hands, feet, ears), heat can be lost or conserved. Countercurrent exchange keeps central body parts warm
HOT- elephants and jack rabbits reduce body temp. by increasing blood flow to ears
COLD- animals reduce blood flow to ears, hands, feet to conserve heat warm blood toward extremity, flows adj. to cold blood moving away from extremity
11
Q
Why do animals require oxygen?
A
Aerobic respiration
12
Q
Respiration
A
Movement of gases into and out of the entire organism; also used to describe cellular respiration, the process of producing ATP within the mitochondria of cells
13
Q
Invertebrate Respiration
Cnidaria: Protozoa and Hydra
A
direct with enivoronment: large surface areas and every cell is either exposed to enivronment or close to it => simple diffusion of gases directly with outside environment (e.g. flatworms). Small animals only
14
Q
Invertebrate Respiration
Annelids
A
- mucous secreted by earthworm provides moist surface for gaseous exchange by diffusion
- circulatory system bring O2 to cells and waste products (CO2) back to skin for excretion
15
Q
Invertebrate Respiration
Arthropods (80% of all living species- insects, spiders, crustaceans (crabs) etc.)
A
- Grasshopper: series of chitin-lined respiratory tubules called trachae open to surface in openings called spiracles through which O2 enters, CO2 exits. No oxygen carrier is needed due to direct distribution and removal of respiratory gases between air and body cells; diffusion across moistened tracheal endings
- Spider: book lungs => stacks of flattened membranes enclosed in internal chamber
16
Q
Invertebrate Respiration
Fish
A
water enters mouth, passes over gills (evaginated structures, create large SA, take O2 and deposit CO; can be external/unprotected or internal/protected, exits through operculum (gill cover).
Countercurrent exchange between opposing movements of water and underlying blood maximizes diffusion of O2 into blood and CO2 into water
17
Q
Plant Respiration
A
- Photosynthesis only takes place during the day
- produces glucose and gives off oxygen
- while respiration requires oxygen to degrade glucose
- Plants undergo aerobic respiration similar to animals
- glucose => 2ATP + 2 pyruvic acid
- gases diffuse into air space by entering and leaving through stomata of leaves or lenticels in woody stems
- anaerobic respiration takes place in simple plants when molecular oxygen is lacking
18
Q
Lungs (invaginated structures)
A
Gas exchange in human: CO2 is transported as HCO3- in the plasma (liquid portion of blood), catalyzed by carbonic anhydrase (CO2 + H20 => H2CO3 => H+ + HCO3-)
Some CO2 mixes direct w/ plasma as gas, or binds with hemoglobin in RBCs
19
Q
Alveoli
A
where gas exchange between the circulatory system and the lungs occurs; surfactant reduces the surface tension
20
Q
Gas Exchange in Human Steps
A
- Nose (filter, moisten, warms incoming air), pharynx (throat-passageway for food and air; dust/mucus swept here for disposal via spitting/swallowing), larynx (voice box- if non-gas enters, cough reflex activates)
- Trachea (epiglottis covers the tracea during swallowing)- ringed cartilage
- Bronchi, Bronchioles: two 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 across moist, sac membranes of alveoli. O2 diffuses through alveolar wall, through pulmonary capillary wall, into blood, and into red blood cells. (CO2 is opposite)
- Bulk flow of O2: O2 transported through body within hemoglobin containing red blood cells (RBCs)
- Diffusion between blood and cells: Oxygen diffuses out RBCs, across blood capillary walls, into interstitial fluids, and across cell membranes (CO2 opposite)
- Bulk flow of CO2: CO2 mainly transported as HCO3- ions in plasma, liquid portion of blood. Produced by carbonic anhydrase in RBCs. CO2 can also directly mix with plasma (as CO2 gas), or bind hemoglobin inside RBCs
- CO2 + H2O => H2CO3 => HCO3- + H+ (via carbonic anhydrase in RBCs
9. Bulk flow of air into and out of the lungs:
a. Inhalation- diaphragm (under lungs) and intercostal muscles (btw ribs) contract/ flattens; increase in volume/decrease in pressure in lungs => bulk flow of air into lungs
b. Exhalation- passive process; decrease in lung volume/ increase in air pressure => air rushes out; diaphragm relaxes and expands
Bohr effect- hemoglobin O2 binding affinity decreases under conditions of low pH (high CO2 and [H+]) => oxygen loads released by hemoglobin
- decrease in CO2 or increase in pH will result in hemoglobin binding more O2
- Result of: CO2+ H2O ⇔ H2CO3 ⇔H+ + HCO3-
- Oxygen diffuses from alveolar air into blood, CO2 diffuses from blood into lungs
- Human respiration is controlled by medulla oblongata; when ppCO2 increases, medulla stimulates increase rate of ventilation
Control of respiration: central chemoreceptors in the medulla and peripheral chemoreceptors in the carotid arteries and aorta moniter CO2 con of blood. In an active body, there is increased CO2 production; it enters plasma is converted to HCO3- and H+, the blood pH drop => respiratory rate increases. Oxygen and pH mainly monitored by chemoreceptors.
21
Q
Chemistry of Gas Exchange
Hemoglobin Structure
A
4 polypeptide subunits, each has a heme cofactor (org. molecule w/ iron atom center)
- Each iron atom can bind w/ 1 O2 molecule
- Via cooperativity: 1 O2 binds =>the rest bind easier. Likewise: 1 O2 released => the rest release easier
22
Q
Chemistry of Gas Exchange
O2 pressure increases
A
O2 pressure increase, O2 saturation of hemoglobin increases
- This is ideal- in the lungs we are O2 rich and want to hang on to it, but in the tissues we are O2 poor (lower O2 pressure) so the hemoglobin will release O2 to the tissues
23
Q
Chemistry of Gas Exchange
O2 saturation of hemoglobin also depends on CO2 pressure, pH, temp. of blood
A
- oxygen dissociation curve shows the percentage of hemoglobin bound w/ O2 at various partial pressures of O2
- curve is shifted right by an increase of CO2 pressure, H+ cxn, or temp (and vice versa) (cadet face right!)
- Bohr effect- hemoglobin O2 binding affinity decreases under conditions of low pH (high CO2 & [H+]) => oxygen loads released by hemoglobin because both O2 and H+ compete for binding at hemoglobin molecule
- 2,3-BPG cxn increase also shifts right: it’s produced in presence of diminished peripheral tissue O2 capacity
24
Q
Metabolic vs. Respiratory acidosis/alkalosis
Chloride shift
A
distinguishable by cause of imbalance
carbonic anhydrase is in RBC’s so at the tissues to balance bicarbonate ions diffusing out of cells (because CO2 enter RBC, carbonic anhydrase converts, bicarbonate diffuses out to plasma)(vice versa at lungs), Cl- enters
- CO2 carried in blood in 3 forms: in physical solution as bicarbonate ion, and in carbamino compounds (combined w/ hemoglobin and other proteins). Majority carried as bicarbonate ion form.
25
Myoglobin
myglobin of muscle has hyperbolic curve (structure doesn't do allosteric cooperative binding, single subunit) saturates quickly and releases in very low oxygen "emergency muscle" situations
26
Fetal hemoglobin curve
shifted left of adult - has higher binding affinity to grab from maternal blood
27
Circulation in Invertebrates
Protozoans
unicellular animal-like [due to movement] protists =\> movement of gas through simple diffusion within cell
28
Circulation in Invertebrates
Cnidarians
body walls 2 cells thick, therefore all cells in direct contact with either internal or external environment.
ex. hydra
29
Circulation in Invertebrates
Arthropods (most insects and molluscs)
**open circulatory system**- pump blood into internal cavity called **hemocoel **(cavities called **sinuses**), which bathe tissues in oxygen and nutrient containing fluid (**hemolymph**). This fluid returns to pumping mechanism (**heart**) through holes called **ostia**.
30
Circulation in Invertebrates
Annelids (earthworms)
**closed circulatory system**- blood is confined to vessels
* also seen in certain mollusks (octopus and squid) and vertebrates
* away from heart: aorta =\> arteries =\> arterioles =\> capillaries
* back to heart: capillaries =\> venules =\> veins
Human and bird hearts have 4 chambers, reptiles and amphibians 3, fish have 2
31
Human heart
1. **Right atrium**: deoxygenated blood enters via superior and inferior vena cava
2. **Right ventricle**: blood moves through right AV/tricuspid valve into right ventricle which contracts and pumps blood into pulmonary artery through the pulmonary semilunar valve
* Ventricle *contracts*, AV valve *closes* to prevent backflow
* Ventricle *relaxes*, semilunar valve prevents backflow from pulmonary artery back into ventricles
3. **Pulmonary circuit**: blood pathway from right side of heart to lungs to left side of heart
* systemic circuit is the circulation pathway through the body between left and right sides of heart
4. **Left atrium**: after lungs the oxygenated blood enters left atrium via pulmonary veins
5. **Left ventricle**: after going through left AV (aka mitral or bicuspid) valve, blood from left ventricle goes to aorta through the aortic semilunar valve into rest of body
* left AV valve prevents backflow into atrium, aortic semilunar valve prevents it into ventricle
right/left AV valves and pulmonary/aortic SL valves
32
Cardiac cycle (rhythmic contraction and relaxation of heart muscles)
regulated by autorhythmic cells initiae contractions independently of nerve cells
* **SA (sinoatrial) node**, or **pacemaker **(located in the upper wall o fright atrium) initiates by contracting both atria and sending delayed impulse to stimulate **AV (atrioventricular) node**
* spreads contraction to surrounding cardiac muscles via electrical synapses made from gap junctions
* pace of SA node is faster than normal heartbeat but parasympathetic **vagus nerve** innervates SA node (also increases digestive activity of intestines); slows contractions
* **AV node**- located in lower wall of the right atrium/interatrial septa; sends impulse through bundle of His =\> passes between both ventricles =\> branches into ventricles via the purkinje fibers which results in contraction
* When ventricles contract (**systole** phase), blood is forced through pulmonary arteries and aorta; AV valves close
* When the ventricles relax (**diastole **phase), backflow into ventricles causes semilunar valves to close.
* Stoke volume = EDV - ESV
33
hydrostatic pressure from heart
causes blood to move through arteries.
* Blood pressure drops as it reaches the capillaries, and reaches near zero in the venules.
* Blood continues to move through veins because of pumping of the heart assisted by movements of adj. skeletal muscles, expansion of atria each time heart beats, and falling pressure in chest when a person breathes.
* Valves in veins prevent backflow.
34
blood vessels
**arteries** which carry the blood away from the heart
**capillaries** which enable the actual exchange of water and chemicals between the blood and the tissues
**veins** which carry blood from the capillaries back toward the heart.
35
arteries
thick-walled, muscular, elastic, pump oxygenated blood away (except for pulmonary arteries that transport deoxygenated blood from heart to lungs)
* wrapped in smooth muscle typically innervated by sympathetic NS
36
arterioles
very small, wrapped in smooth muscle, constrict/dilate to regulate BP and reroute blood - major determinant of pressure
37
capillaries
smallest diameter- single layer of endothelial cells across which gases, nutrients, enzymes, hormones, and waste diffuse
* 4 methods for material to cross capillary wall
* pinocytosis
* diffusion through capillary cell membrane
* movement through pores in cells (fenestrations)
* movement through space between cells
38
venules
small blood vessels that lead back to veins; very thin and porous; drain blood from capillary bed =\> venules combine =\> veins
39
veins
larger veins often have valves to aid in transport of deoxygenated blood back to heart due to fighting gravity (except for pulmonary veins and umbilical vein that carry *oxygenated *blood)
40
Blood flow
* cross sectional area of veins is about 4X higher than that of arteries. Total cross-sectional area of capillaries far greater than that of arteries or veins (capillaries are the narrowest vessels, BUT there are far more capillaries =\> total cross-sectional area of all of them put together is higher than any other cross-sectional area).
* Since blood volume flow rate is approx. constant, **blood velocity is inversely proportional to total cross-sectional area**. Bernoulli's principle tells us pressure is inversely proportional to cross-sectional area, so why is pressure highest from aorta and then continues downward? Blood is not an ideal flow: pumping force of heart is the major contributor to pressure (p=F/A). Aside: arterioles have the greatest resistance to flow (high ability to constrict).
* At any given time, most blood is in the veins/venules, venus sinuses.
41
lymph vessels
* lymphatic system is an open secondary circulatory system- transports excess **interstitial fluids (lymph)** through the contraction of adj. muscles and some walls of larger lymph vessels have smooth muscle
* proteins and large particles that can't be taken up by capillaries removed to lymph; also monitors blood for infxn
* valves prevent backflow- fluid returns to blood circulatory system through 2 ducts located in shoulder region (thoracic and right lymphatic duct)
* **Lymph nodes **contain phagocytic cells (leukocytes) that filter the lymph and serve as immune response centers
42
Blood
4-6 liters in the human body; is a connective tissue
* 55% liquid (**plasma**) and 45% cellular components-plasma is an aqueous mixture of nutrients, salts, gases, wastes, hormones, and blood proteins (immunoglobulins, albumin, fibrinogen, clotting factors)
* Cellular components
* **erythrocytes** (RBCs)-transport O2 (up to 4) on hemoglobin, catalyze conversion of CO2 and H2O to H2CO3- lack nucleus/organelles to maximize hemoglobin content
* **leukocytes **(WBCs)-larger and phagocytize foreign matter and organisms
* diapedesis-the process by which WBCs become part of the interstitial fluid (slip through the endothelial lining)
* **Platelet/thrombocytes-**cell fragments involved in blood clotting- lack nuclei; stick to damaged epithelium; attract more
* convert **fibrinogen **(inactive to **fibrin** (active))
*
43
Process of Blood Clotting
1. Platelets contact exposed collagen of damaged vessel and cause neighboring platelets to form **platelet plug**
2. Both the platelets and damaged tissue release clotting factor, **thromboplastin**
3. Thromboplastin converts inactive plasma protein **prothombrin **to **thrombin **(active)
4. Thrombin converts **fibrinogen **into **fibrin**
5. Fibrin threads coat damaged area and trap cells to form a clot
44
hemoglobin
binds CO w/ much greater affinity than myoglobin (4 subunits vs 1)
45
myoglobin
single chain/protein subunit, stores O2 in muscle
46
myoglobin curve= hyperbolic
hemoglobin curve = sigmoidal. Myoglobin has higher affinity for O2 than hemoglobin. Myoglobin has no change in O2 binding over a pH range
47
Fetal circulation
oxygenated, nutrient-rich blood from placenta carried to fetus via umbilical vein =\> half enters **Ductus venosus **(allows blood to bypass the liver) =\> carried to inferior vena cava =\> RA =\> RV =\> **Ductus arteriosus **(conducts some blood from the pulmonary artery to the aorta [bypassing the lungs/fetal pulmonary circulation]) =\> aorta
Other half enters liver/portal vein =\> RA =\> **Foramen ovale **(allows blood to bypass pulmonary circulation by entering the left atria directly from the right atria since there is no gas exchange in fetal lung) =\> LA =\> LV =\> aorta
48
Cardiac Output
Cardiac Output (CO) = SV (stroke volume) X HR (heart rate)
* *Stroke volume *= volume of blood discharged from the ventricles with each contraction
* *Cardiac Output* = volume dischaged from ventricle each minute.
* Stroke volume = end systolic volume - end diastolic volume
49
Rh factor
another blood antigen; mother might attack Rh+ in 2nd fetus (**erythroblastosis fetalis**) (first child is fine but during 1st childbirth blood exposure =\> antibodies to Rh attack 2nd)
50
Double capillary beds
(portal system) occur in glomerulus, capillaries that surround loop of Henle, small intestine, liver, and hypothalamus and anterior pituitary gland.
Capillary bed pools into another capillary bed (capillary bed 1 =\> drains into portal vein =\> capillary bed 2 =\> drains into vein that returns blood to heart) w/out first going to heart (transport products in high cxn w/o spreading to rest of body)
51
phosphate buffer system
maintains pH of internal fluids of all cells; H2PO4- acts as acid and base (amphoteric)
52
osmoregulation
absorption/excretion of water/dissolved substances (solutes) so that proper water balance (and osmotic pressure) is maintained between the organism and its surroundings
a. _marine fish_: body is hypotonic to environment =\> water is constantly lost by osmosis, constant drinking, rarely urinate, and secrete accumulated salts through gills
b. _fresh water fish_: body is hypertonic to environment; water moves in =\> rarely drink, constantly urinate, and absorb salts through gills
53
Excretory System
Protozoans and Cnidarians
all cells in contact with external, aqueous environment
* water soluble wastes (ammonia, CO2) exit by simple diffusion
* Protists such as Paramecium and amoebas- possesses **contractile vacuole** for XS H2O excretion by active transport
54
Excretory System
Annelids
CO2 excretion directly through moist skin
* nephridia (metanephridia)- occur in pairs within each segment of annelids (earthworms). Interstitial fluids enter a nephridium through ciliated opening **nephrostome **and concentrate through **collecting tubule ** due to selective secretion into surrounding coelomic fluid. Blood that surrounds tubule reabsorb. Water, salts, urea are excreted through **excretory pore**
55
Excretory System
Platyhelminthes
flame cells (protonephridia) distributed along branched tube system that permeates the flatwom
* body fluids filtered across flame cells, whose cilia move fluids through tube system; wastes exit through pores of tube
56
Excretory System
Arthropods
CO2 released from tissues =\> **tracheae** (which are continued with ext. air thru **spiracles**)
* **Malphigian tubules**: occurs in arthropods (terrestrial insects). Tubes attached to mid digestive tract (midgut) collect body fluids from hemolymph that bath the cells; fluids are deposited into midgut. Fluids include nitrogen wastes (in form of uric acid crystals; H2O, salt retained. As fluid passes through hindgut, retained materials pass out of walls and wastes continue down the tract for excretion through anus.
57
lungs (excretion)
CO2 and H2O (g) diffuse from blood and are continually exhaled
58
Liver ( Excretion)
processes nitrogenous wastes, blood pigment wastes, other chemicals, UREA production
59
Skin (Excretion)
sweat glands in skin excrete water and dissolved salts/regulate body temp (sweat gland fxn decreases as we age)
60
Kidney (excretion)
3 regions: 1) outer cortex 2) inner medulla 3) renal pelvis which drains to ureter. Each has many nephrons.
Kidneys =\> ureter =\> bladder =\> urethra. Functions to excrete waste, maintain homeostasis of body fluid volume and solute composition, and help control plasma pH
61
Nephrons
composed of renal corpuscle and renal tubule; rebsorbs nutrients, salt, and water.
* *Renal corpuscle*- glomerulus (sieve) surrounded by Bowman's capsule; afferent arteriole = into glomerulus; efferent arteriole = out of glomerulus
* After efferent arteriole passes back out of the glomerulus is just webs around the entire nephron structure (see above) as the peritubular capillaries (surround PCT and DCT; reabsorb stuff) and vena cava (surround LOH in medulla, maintian cxn gradient) before dumping back in to the renal branch of renal vein. Meanwhile, Bowman's capsule leads to....
* *Renal tubule*
* **Proximal convoluted tubule**- *active *reabsorption of glucose, ions, amino acids begins (water follows =\> cortex not salty)
* **Loop of Henle**- (majority of nephron)
* DESCENDING- only permeable to water (but this water is picked up by vasa recta =\> medulla stays salty)
* ASCENDING makes renal medulla *salty*- actively pumps out Na+, K+, Cl-; impermeable to water!
* This process allows reabsorption of 99% of filtrate =\> conc. urine
* **Distal convoluted tubule**- more reabsorption of glucose, ions, water, etc (cortex not salty). Filtrate: Na+ and Ca2+ get resorbed into body, K+/H+/HCO3- secreted out via tubule. Distal tubule empties to...
* **Collecting duct**- collects remaining filtrate, is ordinarily impermeable to water unless ADH acts on it
* descends to medulla (salty part), where *antidiuretic* hormones (**ADH/vasopressin**) can make MORE water leave from urine by increasing permeability of collecting duct =\> urine even more concentrated. 1 CD shared by many nephrons
* also, aldosterone acts on DCT and CD: increase Na+ resorption, K+ secretion =\> water passively folllows Na+
62
Urine Formation
filtration, secretion, and reabsorption
63
Filtration (Urine Formation)
fluid that goes through glomerulus (afferent arteriole =\> glomerulus =\> efferent) to the rest of the nephron is called filtrate; particles that are too large to filter through (blood and albumin) remain in circulatory system: passive process; driven by hydrostatic pressure of blood. So Glomerulus =\> filtrate pushed into Bowman's.
64
secretion
substances such as acids, bases, and ions (K+) are secreted by both passive/active transport; secreted from *peritubular capillaries*.
65
Reabsorption
glucose, salts, AA, and water are reabsorbed from filtrate and return to blood; takes place namely in PROXIMAL convulated tubule (active)
66
Concentration
when dehydrated volume of fluid in bloodstream is low so you need to make small amounts of concentrated urine =\> ADH prevents water loss by making distal tubule permeable to water/// when Blood Pressure is low =\> aldosterone increases reabsorption of Na+ by distal nephron which increases water retention (serum [Na+] increases BP)
67
Urine Formation (Recap)
filtration occurs in renal corpuscle =\> reabsorption/secretion mostly in proximal tubule =\>filtrate becomes more cxn as it moves down loop of Henle (water passive out of tube) =\> more dilute as it moves up loop (passive and active transport of salts out, but not water) =\> DCT dumps into collecting duct =\> filtrate more cxn again as it descends collecting duct (because surrounding medulla is salty, water leaves) =\> CD leads to renal calyx =\> drains to ureter. Keep in mind reabsorb means back into the body
68
Juxtaglomerular Apparatus
monitors filtrate pressure in DT via granular cells =\> secrete renin =\> angiotensin cascade =\> tells A.C. to make aldost.
69
Antidiuretic hormone (ADH)
increases the reabsorption of water by the body and increases the concentration of salts in urine. It increases the permeability of the *collecting duct to water*. As a result, urine becomes more concentrated as water diffuses out of the collecting duct as the filtrate descends into the renal pelvis
70
Aldosterone
increases both the reabsorption of water and reabsorption of Na+. It increases the permeability of the *distal convoluted tubule and collecting duct to Na+. *More Na+ diffuses out of this tubule and duct.
71
What establishes an osmolarity gradient in the surrounding intersitial fluid (excretory system)?
selective permeability of the tubules
72
Urine
hypertonic to the blood and contains a high urea and solute concentration
73
osmolarity gradient
created by exiting/ entering of solutes; increases from cortex to medulla
74
Counter Current Multiplier
descending loop permeable to water and asceding is permeable to salts/ ions; this makes the medulla very salty and facilitates water reabsorption
75
Nitrogen as Waste
Aquatic animals excrete NH3 or NH4 directly into water, mammals convert NH3 to urea
76
Excretion in birds/insects/reptiles
convert urea to uric acid (insoluble in water, water conservation, excreted as solid)
* allantosis = special sac in bird egg that keeps N waste away from embryo
77
Excretion in Plants
excess CO2, waste O2, and H2O(g) leave by diffusion through stomata and lenticels
* this process is called transpiration
78
Digestive System:
Unicellular
**Amoeba**: Food capture: phaogcytosis =\> food vacuoles
**Paramecium**: cilia sweep food into cytopharyx =\> food vacuoles forms and moves toward anterior end of cell
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Digestive System:
Invertebrates =\> Physical and Chemical Breakdown
* Physical breakdown**- ***cutting/grinding in mouth; churning in digestive tract
* Chemical breakdown- *enzymatic hydrolysis =\> smaller nutrients =\> pass through semi-permeable membrane of gut cells to be further metabolized
80
Digestive System
Cnidarians
hydra- intracellular and extracellular digestion
81
Digestive System
Annelids
earthworms-one way digestive tract
* crop - food storage
* gizzard- grind food
* intestine - contains **trypholosole **to increase surface area for absorption
82
Digestive System
Arthropods
also have jaws for chewing and **salivary ****glands**
83
Digestion in Humans
Four groups of molecules encountered
1. Starches =\> glucose
2. Proteins =\> amino acids
3. Fats =\> fatty acids
4. Nucleic acids =\> nucleotides
84
Digestion in Humans
Digestion Steps
1. **Mouth**- salivary a-amylase breaks down (starch =\> maltose), chewing creates **bolus** which is swallowed
2. **Pharynx** (throat)- this is where food and air passages cross; the **epiglottis**, flap of tissue, blacks trachea so only solid and liquid enter..
3. **Esophagus**- tube leading to stomach, food travels by contractions (**peristalsis**)
4. **Stomach**-secretes **gastric juice** (digestive enzymes and HCl)- food enters stomach through lower esophageal/cardiac sphincter. The stomach also contains **exocrine glands** (local secretion by way of duct) within gastric pits (identations in stomach that denote entrance to the gastric glands, which contain secreting chief cells, parietal cells, and mucous cells (secrete mucus to prevent backwash)
5. **Small Intestine**
6. **Large intestine**
85
Digestion in Humans
Stomach
secretes gastric juice (digestive enzymes and HCl)- food enters stomach through lower esophageal/cardiac sphincter. The stomach also contains exocrine glands (local secretion by way of duct) within gastric pits (identations in stomach that denote entrance to the gastric glands, which contain secreting chief cells, parietal cells, and mucous cells (secrete mucus to prevent backwash)
a. **Storage**- accordian-like folds allow 2-4 liters of storage
b. **Mixing**- mixes food w/ H2O and gastric juice =\> **chyme **(creamy medium)
c. **Physical breakdown**-muscles break food; HCl denatures proteins and kills bacteria
d. **Chemical breakdown**- **pepsin** (secreted by **Chief cells**) digests proteins; (pepsinogen activated by HCl, which is secreted by **parietal cells**)
i. **peptic ulcers -** caused by failure of mucosal lining to protect stomach; ulcers can be caused by excess stomach acid or H.pylori as well
e. **Controlled release**- chyme =\> small intestine; controlled by **pyloric sphincter**
f. **Stomach cells**
i. mucous cells- secrete mucus that lubricates and protects stomach's epithelial lining from acid environment
ii. chief cells- ex. gl. secrete pepsinogen (zymoegen precursor to pepsin); pepsinogen activated to pepsin by low pH in stomach; once active begins protein digestion
iii. parietal cells- secrete HCl; intrinsic factor (B-12 absorption)
iv. G cells- secrete **gastrin**, a large peptide hormone which is absorbed into blood =\> stims parietal cell to secrete HCl
v. affected by: A-chol increases secretion of all cell types, gastrin and histamine increase HCl secretion
86
Digestion in Humans
Small Intestine
food goes from stomach to small intestine through the **pyloric sphincter**- first 25 cm (**duodenum**), continues breakdown of starches and proteins as well as remaining food types (fats and nucleotides); ileocecal valve between it and large intestine. Structure is duodenum (most digestion), jejunum, then ileum (jej and il mostly absorption). 90% of digestion and absorption occurs in SI; completes.
87
Digestion in Humans
Small Intestine
* **Structure **wall has finger-like projections called villi that increase the surface area for greater digestion/absorption. Each villi has a **lacteal** (lymph vessel surrounded by capillary network; both fxn for nutrient absorption). Villi have microvilli, more SA
* Goblet cells secrete mucus to lubricate and protect from mech/chem damage
* Duodenum has ph ~6 mainly due to bicarbonate ions secreted by pancreas
* **Enzyme origin** small intestine- proteolytic enzymes: proteases, maltase and lactase, phosphatases/nucleosidases (nucleotides); lipase
* **Pancreas** secretes bicarbonate; also acts as exocrine gland releasing major enzymes from acinar cells via pancreatic duct =\> duodenum
* Trypsin and chymotrypsin (proteases), lipase, pancreatic amylase, deoxy and ribonucleases
* All exist as zymogens/proenzymes (inactive) first. Trypsin gets activated, then activates the other enzymes
* These enzymes in alkaline solution (pancreatic duct =\>duodenum)
* **Liver **produces bile (no enzymes, emulsifies fats) stored in **gall bladder**, flows thru bile duct which merges with pancreatic duct
* **Remainder of Small Intestine **(6m) absorbs breakdown products (**villi **and **microvilli**)
* **Chyme **moves fthrough intestines via peristalsis as well. Segmentation (2nd type of intestinal motion) mixes chime w/ dig. juices
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Digestion in Humans
Large intestine (colon)
reabsorption of water and salts to form **feces**; 1.5 m long
## Footnote
a. Feces stored at end of L.I. in the **rectum** =\> excreted through **anus**
b. At beginning is **appendix**, which in herbivores is large **cecum** (cellulose digestion) with the help of bacteria
c. Bacteria (e.g. E.Coli) a **symbiont **in large intestine = main source of **Vitamin K **(also Vitamin B)
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Enterochromaffin Cell (ECL)
neuroendocrine cells in the digestive tract; gastrin stimulates them to release histamine which in turn stimulates parietal cells to produce gastric acid
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Hormones involved in Digestive Process
Gastrin
produced by stomach lining when food reaches or upon sensing of food
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Hormones involved in Digestive Process
Secretin
produced by cells lining duodenum when food enters; stimulates pancreas to produce bicarbonate (neutralizes the chime)
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Hormones involved in Digestive Process
Cholecystokinin
produced by S.I. in response to fats; stimulates gallbladder to release bile and pancreas to release its enzymes
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Hormones involved in Digestive Process
Gastric Inhibitory Peptide
produced in response to fat/protein digestates in duodenum; mild decrease of stomach motor activity
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Digestion in plants and fungi
plants have no digestive system, but intracellular processes similar to animals to occur
**intracellular digestion**- store primarily **starch** in seeds, stems, and roots; when nutrients are required, polymers are broken down (into glucose, fatty acid, glyercol, and amino acids) by enzymatic **hydrolysis**
**extracellular digestion**- several plants must obtain nutrient from environment
* **Fungi**- **rhizoids **of bread mold, secrete enzymes into bread, producing simple digestive products which are then absorbed by diffusion into rhizoid
* **Venus flytrap**- enzymes digest trapped fly (serves as **nitrate** source); \*\*\*still autotrophic)
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Liver functions
* Blood storage
* Blood filtration
* carbohydrate metabolism
* Protein metabolism
* Erythrocyte destruction
* Vitamin Storage
* Glycogenesis, glycoenolysis
* Blood acidity
* Digestive; Transport
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Liver functions
Blood filtration
kupfer cells phagocytize bacteria picked up in intestines
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Liver Functions
Carbohydrate Metabolism
liver maintains normal blood glucose levels via **gluconeogenesis **(production of glycogen and glucose from noncarb precursors), **glycogeneis**, and storage of glycogen
* all carbs absorbed into blood are carried by **portal vein** to the liver. Absorbed gal and fru converted to glu, then stored as glycogen
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Liver Functions
Protein metabolism
liver deaminates AA's, forms urea from ammonia in blood, synths plasma proteins, synthes nonessential AAs
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Liver Functions
Detoxification
Detox'd chemicals, excreted by liver as part of bile (or polarized to be excreted by kidneys)
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Liver Functions
Erythrocyte destruction
kupfer cells destroy irregular erythrocytes (but most are destroyed by spleen)
