Lesson 1: History of Biobehavioral Health, and Scientific Inquiry PDF

Lesson 1: History of Biobehavioral Health, and Scientific Inquiry 1 History of BBH 1 Hippocrates & Galen — Hippocrates came up with an observational approach to medicine which is the humoral theory he believed that the body is balanced by humors (black bile, yellow bi...

Lesson 1: History of Biobehavioral Health, and Scientific Inquiry 1 History of BBH 1 Hippocrates & Galen — Hippocrates came up with an observational approach to medicine which is the humoral theory he believed that the body is balanced by humors (black bile, yellow bile, blood, phlegm) he did not believes spirits/demons were the cause like many of the others did during his time period. ex. people who were suffering from depression is what he associated with black bile, people who had fevers he believed were associated with exxesive blood so he used processess such as blood letting which was common until the 1800s — Galen was another greek physician who was inspired by Hippocrates. He created medicines that could be used to treat excessive amounts in any of the four humors associated with the humoral theory. Galen was also infuential in today’s views of autonomy he gained knowledge and wrote it down form treating the wounds of different gladiators. Additionally he also performed many vivisections (alive disections) on animals that helped influence autonomy as well. He had many writings and was influential in the world of meds for 1300 years. 2 Middle Ages & the scientific revolution — during the middle ages which was the after the fall of the Roman empire 5th-15th century scientific thinking stagnated bcuz indiivduals thought that they were being divinely punished by God. However during the late rennisance european of the 14th century that mindset began to change with the advancements in art, biology, and astronomy. Due to this rapid advancement this time was coined as the beginning of the scientific revolution ▪ Reductionism - was the dominant of approach to science during the scientific revolution it involves taking complex systems and breaking them down into component parts in order to understand how they function (ex. they would break the body into systems such as immune, cardiovascular, and respiratory to understand how it functions as a whole) 3 Cell theory & germ theory — Cell Theory is the idea that cells make up all living things, cells are a fundamantal unit of life, and that cells form from pre-existing the cells and the theory was created by schwann and scheleiden —— Germ Theory is the idea that microorganisms/germs are the cause of the spreading of sickness/illness/disease ▪ What was Pasteur's role? — Pasteur basically debunked spontaneous generation (living things form on non-living material) he used food in order to do so & it showed when it was sealed it did not spoil — he also created pasteurization (process of storing food at high temps to keep it) 4 Smallpox, Jenner, & vaccines — Smallpox are red lesions of bumps that first form on the mucous membrane and spread to the face and body they used to kill 1-7 people but it reduced to 1-40 in the past but it is now completley eradicated. The person that first introduced inoculations was an african slave named Onesimus and he told his master Mather that he had protection from smallpox bcuz of a procedure he got done in Africa where somone rubbed their pus from it onto an open wound of his. Mather was able to make this widespread with the Boston epidemic and out of the 242 that were inoculated only 6 people died — In the late 1700s Edward Jenner did an unethical experiment on an 8 year old boy (phillip) where he exposed him to cowpox to give him immunity to smallpox and then he exposed the boy to smallpox but he did not catch it he also did this with 23 others and got the same results. Jenner coined the term Vaccine but vaccines were not popular until the 1900s  5 Antibiotics - Alexander Fleming was responsible for the discovery of antibiotics because he discovered a fungus that had penicillum in it but he found it hard to isolate ppl were eventually able to in the 1940s and this gave rise to antibiotics — even so some antibotics are not as useful today because bacteria has become more resistant to it 6 What is the biomedical model? — This model is the idea that disease and sickness come from biological pathogens such as germs & parasites — this model was very helpful in aiding the scientific discovery of ways to stop exposure to certain pathogens and due to this the lifespan was able to expand from people dying in their 50s during the 1900s to people living to be 80+ in 2011 ▪ What are the problems with it? — The problem with the biomedical model is that it only accounts for biological factors it does not take into account sickness that are not caused by pathogens like diabetes and cardiovasular disease — stress and other areas of life such as culture and genetics can cause sickness as well so scientists felt that it was incomplete even though it was very beneficial during the first half of the 20th century 7 What is the biobehavioral model and why may it be more suitable than biomedical? — The biobheavioral model accounts for biological factors, social well-being, envrionment, culture, genetics, 2 Scientific Inquiry 1 Cognitive biases — they are the result of our minds creating shortcuts or automatic explanations — we automatically believe that two things are associated bcuz they happened one after the other we think there is automatically a connection (ex. having a headache & taking aspirin before bed & waking up with the headache gone but the aspirin was a sugar pill so there is an alternative explanation ie sleep brain tricking you) for these reasons we need different measurements because our perception and cognitive bias can trick our brains into thinking that there is an association 2 Hypothesis testing ▪ Scientific method — 1. observation 2. forming an hypothesis 3. experimenting/testing that hypothesis — the scientific method has been around since the 1600s & it is a reliable form of measurement — hypothesis testing does not automatically make something a fact it has to go through numerous tests to see if there are similar results that either prove/refute the obsrvation ▪ Hypotheses vs. theories — hypotheses are speculative explanations/predictions that have not gone through rigourous testing/experimenting — Theories are hyothesis that have gone through numerous amounts of tests and have been proven right (ex. evolution) mult. experiments done to pove it right 3 Statistical testing ▪ Samples & p-values ▪ What is the difference between a sample and a population? — samples are a a group of people that are recrutied to volunteer to be a representation for the population — the population is the actualt group of people as a whole (ex. if they were doing a study on mothers the sample would be the group of moms in the study and the population would be like all mothers in america as a whole ▪ What is the typical threshold for statistical significance in terms of p-values? — the typical threshold for statistical significance is is 0.05 because anything greater than that means that the research is not significant below that means that the research was statistically significant 4 Causality — determining whether or not one thing causes another (needs to be proven through scientific measurmenets — causality is important to expeirments because it is used to determine if one variable causes another or if the exposure/IV is really what is influencing the outcome/DV ▪ Correlation vs. causation — Correlation is when things are correlated but there is no causality between the two variables (ex. ice cream sales and shark attacks are correlated but they do not have causility that actual causality would be the fact that it is how and ppl are more likely to swim or eat ice cream during that time) causality is when one variable is actually causing another intimacy causes pregnancy in straight couples 5 Bias & confounds ▪ Importance of replication — replication is important to eliminate bias in the experiment as well as confounding variables that can lead the experiment to have complications — with replication they have multiple samples and researchers run the same investgation to eliminate these bias and confounding variables to see if they get the same result across the board — r Lesson 2: Research Methods & Applications 1 Research Methods 1 Know the essential terms — dependent Variable is the outcome variable and it is depends on how someone reacts to the indpendent variable/exposure — Independent variable is the exposure or the variable that changes the outcome of the dependent variable — Prevalence is how prevelent a certain behavior or disease is for a certain period in time its common in epidemology & what portion of the population is affected or how common is this behavior or health condition in this population (focus on number of existing cases) — Incidence is also common in epidemology but its all the new cases of that health behavior or health condition during a certain period of time (focuses on number of new cases) 2 Case study/series ▪ Know design — A case study is the analysis of one individual person/case & the person usually has an unusual condition (meaning that it is unusual or significant enough to warrant a study (lady with missing cerebellum able to walk normally only had diziness and nausea) —- Case series are a collection of case studies of indiivduals suffering from the same unsusal condition & these are done to raise awareness of a particular issue ▪ Can't examine cause & effect — they help to bring attention/awareness to the case but they cannoot determin causality because you would need multiple groups to compare to one another and case studies are not doing this its only studying the actiona & behaviors of one individual so there is a high risk of confounds you would need a more advanced study design 3 Cross-sectional study ▪ Know design — cross-sectional studies are studies conducted on one sample of people at one point in time so you only know about things that are currently happening with them — it can help obtain estimates of prevalance making it useful for gathering information  ▪ Can't demonstrate causality — they cannot demonstrate causality because they do not have any follow up for the people so something couldve have changed within the coming days/months/years but since there is no follow up it cannot determine causality ▪ Can use correlation — you can obtain correlational data from cross-sectional research but you cant determine causality ▪ Know uses and interpretation of correlation statistics — positve correlation is when both vairables are going up — negative correlation is when one variable goes up as the other goes down — this is the correlation coefficient 4 Case-control study ▪ Know design — a case control study has a case group and a control group — the case group already has the issue for instance the case group has diabetes while the control group does not and they compare sleeping issues between the two groups to see if those with diabetes have worst sleep like they think ▪ Can't demonstrate causality — case-control studies cannot determine causaility because they use cross-sectional data from one group at a certain point in time with no follow-up ▪ Often uses odd ratio to eliminate risk (know how to interpret) — case-control studies use the odds ratio & with the odds ratio it starts at zero and goes up so if its a odds ratio of 5.0 you would say that individuals are 5 times more likely to get diabetes if they have poor sleep habits — if its 1.0 that indicates that there is lower frequency of the outcome occuring 5 Cohort study ▪ Prospective — wants to determine whether the exposure preceded the outcome & determin causility ▪ Know design — cohort studies use data from two groups of people who do not have the outcome so they would both be starting out with no lung cancer but one of the groups smoke while the other does not and they have follow-up so they see if there are any changes for years to come to see if anyone in the exposure group has developed lung cancer or if anyone that has not been exposed to smoking has developed it ▪ Can support arguments for causality — it can support arguments for causality because they are doing follow-up with the groups which is crucial for wanting to see if there is an actual cause and effect among the variables — plus data is longitudianal meaning its gathered over months/years — but its still not the best for determining causality experimental designs are ▪ Often uses risk ratio to eliminate risk (know how to interpret) — cohort studies use relative risk aka risk ratio to eliminate risk in the data — if its 1.0 it represents an increase in risk if its 10.0 it represents a 10-fold increase in risk 6 Experimental studies ▪ Best for identifying causal relationships ▪ Experimental vs. control group — the experimental group recieves the exposure/independent variable while the control group does not they would recieve a placebo instead ▪ Random assignment - must be purely random — even small things such as grouping by the first letter of the last name can cause issues because it could lead to confounding variables that can impact the experiment on the bases of race, gender, age etc.  ▪ Blinding ▪ Single vs. double vs. triple — single blinding is when pariticpants dont know, double blinding is when partiicpants & researchers dont know — triple blinding is when participants, researchers, & analyzers don’t know ▪ Good placebo - what makes a good placebo — a good placebo must be identical to the actual medicine or treatment given the the experimental group — this can stop the control group from having any differences that could impact the experiment so that placebo has to be convincing 7 For all study designs, plan to be able to look at an example study scenario and say what type of study design is being used! 2 Research Applications 1 What does it mean for something to be peer-reviewed? — peer reviewed means that an article has gone through rigourous reviews from other experts in the field before it gets published to a scientific journal to make sure that the scientific research is of high quality/standards 2 Types of publications ▪ Look at examples and plan to be able to identify what type of publication something is by looking at an abstract (like the examples on Canvas) — literature reviews, meta-analysis, empircal studies, and ??? Lesson 3: Neurobiology & The Endocrine System 1 Neurobiology 1 CNS vs. PNS — the central nervous system is made up of the brain and spinal cord and the the nerves that connect the brain and the spine to send messages the brain processes sensations (such as touch, taste, smell) & it also creates thoughts that the body can act out as the messages are sent down — the Peripheral nervous system is the all the nerves that connect the spine to the rest of the body to cause muscle contractions ▪ Somatic/autonomic & sympathetic/parasympathetic distinctions — the peripheral nervous system has two section & they are the somatic which is responible for all voluntary movements in the body and it starts with a thought it will travel down the spine to the nerves connected to the muscles to cause muscle contractions for movement —- the automic nervous system is another branch of the peripheral nervous system & it is responible for all automatic things that we do such as breathing, respiratory system, digestion — there are two branches to the automic system and they are the sympathetic (fight-or-flight) & the parasympathetic (rest-and-digest) 2 Neuron structure & function ▪ Dendrites — they are the branches of a neuron and they are used to recieve messages from other neurons and the denrites will send these neurotransmitters down if they have an electrical impulse ▪ Cell body — after the electrical impule is sent down from the dendrites it will travel to the cell body/soma where it can then become an action potential if the electrical impulse is strong enough after that it would go to the next step ▪ Axon — after leaving the cell body/soma it will travel down the axon to the other end of the neuron  ▪ Myelin — the axon is coated in a myelin substance to prevent the action potential/electrical impulse from dying or weakening as it travels down the neuron ▪ Axon terminal — after it travels down all the way it reaches the axon terminal/synaptivc bouton where it will meet with the branch of another neuron to send the information over ▪ Synapse & synaptic cleft — the synapse is where the information is transfered from the neuron to the dendrites of another neuron and the process repeates — the synaptic cleft is the space between the two neurons that are sending information & its about 10-20 nanometers 3 Gross anatomy - for all brain regions, know general function as indicated in lesson content ▪ Cerebral hemispheres — there are two cerebral hemispheres of the brain and they are responsible for different things but most functions happen across multiple areas of the brain ▪ Cerebral cortex — the cerebral cortex is the part of the brain that looks like a lump of worms & it is the most important area when it comes to complex cognitive functions ▪ Lobes — the brain has 4 lobes temporal, pariteal, frontal, & occipital — they can repsonible for different functions (ex. occipital handles most vision functions) but different actions use multiple lobes in order to occur) ▪ Brainstem — the brainstem is what connects the brain to the spine — but its also able to help maintain the respiratory system & regulate the heartrate ▪ Cerebellum — the cerebellum is the potruding mass at the back of the brain and it is known to help with maintaining balance/eqilibrium but it can also hold memories & emotions ▪ Hippocampus — we have two hippocampi in the temporal lobes of the brain & they are reponblible for helping to create memories or remember things in general — indivduals who suffered from damage to the hippocampus has severe disturbances in their memories ▪ Amygdala — the amygdala helps us to process emotions such as fear and we have two of them one is located in each hemisphere of the brain — its almond shaped and its a collection of nuclie ▪ Reward system ▪ Dopamine pathways — VTA ▪ Ventral tegmental area — an area in the brainstem where dopamine neurotransmitters are ▪ Nucleus accumbens — the dopamine neutrotransmitters are sent to nucleus accumbens down the axon where they trigger a pleasure response (intmacy, addictive drugs, food) 2 Endocrine system 1 Hormones — hormones are the main signaling molecule of the endocrine system hormones can come from neurons but they are mostly released & synethesized by structures in the endocrine system — endocrine meaning secreting internally meaning that endocrine releases within the body and not outside and it does this by using endocrine glands that are placed throughout the body 2 Hypothalamus & homeostasis — the hypothalamus is a small but important collection of nuclei above the brainstem and it is responible for homeo stasis and hormone release — homeostasis is the process of maintaining equlibrium and contunuity keeping the body at its typical levels. ex. if the body temperature is too high it can activate sweat so we can cool off 3 Pituitary gland — it extends from the hypothalamus its the size of a pea and it is responible for the production and secretion of many important hormones in the body ▪ Relationship with hypothalamus & role of releasing hormones — the hypothalamus affects behavior through hormone relrease and it does so with the use of the pitutitary gland because it controls the release of hormones through the gland ▪ Anterior pituitary — ▪ Synthesizes and secretes hormones in response to releasing hormones — when the body needs a certain hormone it will signal hormone release from the hypothalamus to the anterior pitutary and that will cause it to release into the bloodstream to the body ex. if the hypothalamus detects a need for increase in the growth hormone it well send the hormone-releasing hormone to the anterior pituitary through the hypohyseal portal system and it will cause it to secrete & release the hormone into the bloodstream so the anterior pitutarty creates hormones but the release to the bloodstream is controlled byt the hypothalamus ▪ its the front part of the of the pitutitary gland and it produces hormones that are crucial for normal physiological functioning such as ATCH, growth hormone, lutenizing hormone, follicle hormone, prolactin, beta-endorphon, thyroid stimulating hormones ▪ Posterior pituitary ▪ Vasopressin & oxytocin (synthesized in hypothalamus but secreted from posterior pituitary) — ▪ unlike the anterior pitutary it cannot make its own hormones but it can secrete 2 hormones from the hypothalamus and they are vasopressin and oxytocin — these two hormones are made in thh cell body of neurons located in the hypothalamus they travel down he axon to the posterior pitutary where they are stored until they’re released into the bloodstream through the secretion from the posterior pitutary ▪ oxytocin was first recognized in women for rile in contractions during labor as well as lactation but has more broad role in positive social emotions like bonding and compassion ▪ Vassopressin is an anti-dieretic hormone (ADH) best known for its effects on kidneys causing water reabsorption to decrease urine output when more fluid is needed in the body and has a role in regulating blood pressure 4 Example: Stress response/HPA axis ▪ Know the hormones involved and the direction of the cascade — hypothalamic-pitutary-adrenal ▪ the classic cascade of hormones uses multiple glands from the endocrine system it starts when we experience a stressful event the sympathetic nervous system and the endocrine system is triggered — the hypothalamus will release CRH to the anterior pitutary travels down the hypophyseal portal system causing it to create and secrete ACTH after that it travels down to the two endocrine glands on top of the kidneys and they are the adrenal glands where it releases the final hormone cortisol when its high enough in the blood it signals the hypothalamus to stop production of CRH to end the process/cascade Lesson 4: Immune System & Other Bodily Systems  1 Immune System — for the body to function properly it has to be free of sickness and disease and the immune system is a collection of organs that acheives so its a collection of organs and structures throughout the body 1 Antigens & pathogens — the organs in the immune system repond to the antigens and pathofens which are germs, bacteria, allergens — antigens are components of pathogens 2 Nonspecific immune system — protects the body from things that dont belonw (pathogens, pollutants, dust) ▪ Innate defenses — the nonspecific immune system is innate meaning we are born w/ it ex. cilia lines the nose/respiratory system to filter out dust & microorganisms — stomach line w/ acid to kill microorganisms & the skin acts as largest barrier to many foreign substances ▪ Cells & proteins ▪ Macrophages — large white blood cells that travel between fluid of cells they consum foreign substances and cells infected by pathogens ▪ Natural killer cells — white blood cells that search for cells displaying signs of infection and destroys them to limit spread of pathogens ▪ Interferon — interferones are proteins made from calls already infected w/ virus they signal to other cells that there is an infection so that they can prepare to defend against the spread ▪ Inflammatory response — part of the nonspecific immune system happens w/ cut or any tissue damage the cells that were damaged release histamine to cayse increase in bloodflow (red, heating, swelling) the plasma that leaks as a result carries white blood cells & clotting proteins to damaged area to fight bactera and to help speed recovery sealing off the wound through clotting 3 Specific immune system ▪ B cells — they are trained to recognize antigen and intitate mechanisms to get rid of them ▪ Plasma vs. memory— plasma cells are when a b-cell is formed its trained to recognice one specific antifent after that the antigen binds to the receptors on the surface of the b-cell this creates more of the b-cells to copy the parent cell & recognice the antifens and they secrete antibodies to destroy the invader/antigen (plasma cells only last for a few days) —— Memory b-cells are sometimes formed during this same process and they can last for decades so if you are exposed to the same virus twice in the same flu season and you caught it you are less likely to catch it ▪ Which cells are involved in developing immunity after vaccination — memory b-cells are involved in immunity after vaccination ▪ What are the characteristics of a secondary immune response? — memory b-cells after you catch a virus if you caught it again your body will recognize it and be able to respond better resulting in quicker recovery and less severity ▪ T cells ▪ Cytotoxic & helper T Cells — cytotoxic t-ce;;s bind to the surface of cells infected w/ an antigen after that they produce protein perforin to bind to the membrane of the infected cell to rupture/kill it —- Helper t-cells they detect infected antigens on macrophages and after they signal an imune response by signaling cytotoxic t-cells and stimulating b-cells to coordinate an attack on the foreign substance — immune response 4 Immune organs ▪ Bone marrow — is a spongy tissue found deep within some bones in the body its where t-cells b-cells and other white blood cells are formed for the immune system (b-cells mature in the bone marrow) ▪ Thymus — T-cells are produced in the bone marrow but they mature in te thymus located behind the breastbone this is where they learn to recognize antigen which is crucial for younger years but as you become a teenager the organs atrophy so its not as important as you get older but t-cells mature here for life ▪ Spleen — the spleen is located under the left ribcage — the main function of the spleen is filtering blood that is delivered via the splenic artery and the white blood cells act to get rid of antigens — the spleen is a resivoir for immune system cells so once antifens appear they can destroy them & alert the rest of the body 5 Lymphatic system — collection of vessels nodes & organs that stretch throughout the body the cessels contain lymph which is used to return fluids from tissue to the circulatory system — lymph carries fluids from between cells to the circulatory system to kidney shaped organs lymph nodes they have a collection of white blood cells that can kick off specific & nonspecific immune system ex. when sick the lymph nodes swell due to white blood cells accumulating to attack 6 Immune to brain circuit ▪ Sickness behaviors — the nervous system is used to combat disease w/ immune system — sickness behaviors can be beneficial bcuz inactivity allows immune system to have energy reserves it can use to raise the body temp — no appettite can help because reduces nutrients like iron available in the gi tract to feed invading microbes the brain is signaled through cytokine they are produced from immune cells and they bind to recepts on nerve cells that carry signals to the brain to inform of infection and activate sickness behaviors 2 Cardiovascular, respiratory, digestive 1 Cardiovascular — the primary role of this system is to carry oxygen to the cells and remove waste (carbon dioxoide) from the cells — transports oxygen & nutrients to cells ▪ Types of vessels — 1. arteries: they carry blood away from the heart either to the lungs or throughout the body — 2. Veins: return blood to the heart — 3. cappallaries: small vessels w/ thing walls that allow oxygen and nutrients to pass through them & surrounding tissue and waste like carbon dioxide to pass between them and surrounding tiusse ▪ Contents of blood: plasma, red blood cells, white blood cells, platelets — blood composition— the blood contains numerous cells and cell components suspended in fluid called plasma. most of the cells in the blood are red blood cells and they each contain proteins called hemoglobin they are unique because iron can bind to it making them able to carry oxygen to the cells that need it ex. ppl w/ blred blood cell defiency or hemoglobin defiency issues often have low iron causing them to have weakness fatigue and other symptoms — white blood cells help to defend the body from foreign invaders — platelets are small pieces of cytoplasm that play a significant role in causing blood clotting to stop blieedings they plug up damaged walls of the blood vessel fluids of the blood is plasman its 90% water 10% other proteins salts subtastances ▪ The heart  ▪ the organ that keeps blood circulating through the body it is in the center of the chest and its the size of a closed fist tilts slightly to the left ▪ Cardiac cycle 1 Diastole vs. systole — the first phase of the heart cycle is the diastole phase the heart is relaxed as oxygenated blood comes in from the lunds and deoxygenated blood comes from the body during this phase the heart fills with blood the second phsase is the stytole phase were the heart contracts and deoxygenated blood is sent to lungs & oxygenated to blood to the body 2 Blood pressure & heart rate — the healthy heart rate is 60-100 bpm and the blood pressure is 120/80 sty dy when its higher than this it can cause increase risk of blood causing damage to blood vessels lining or arthersocerosis ▪ Sinoatrial node/pacemaker — the pace maker is what helps to regulate the heart contractions by sending electrical signals for the heart to contract 1 Respiratory ▪ Respiratory tract runs from mouth/nasal cavity to lungs —the main responibility of the respiratory system is to bring oxygen in the body through inhalation through nose or mouth after that air moves to the next section the pharnyx then to the larnyx where the vocal cords are located et they are folds of tissue that vibrate when we exhale after that it passes through the bronchioles at the end of the branchioles are small sacs called aveoli and they collect the air oxygen afer cappallariesf orm a mesh around tehe aveoli to transfer the gasses where it diffuses carbon dioxide for exhalation — pathogens polluntants can get in throguh the respirtory tract to damage our ability to extract oxygen from air ▪ Alveoli - sites of gas exchange — they are sacs at the end of the bronchioles they collect air and oxygen after cappa;llaries form a mesh around aveoli to transfer the gasses where it diffueses carbon dioxide to extract for inhalation 2 Digestive ▪ Mouth— digestion begins as soon as food enters the mouth the salivary amylase breaks down the starch we consume than the tongue helps to push food back to the pharnyx to swallow ▪ Stomach — tfood travels to the stomage down a long tube called the esophagus to reach the somach the stomach secretes substances that aid in digestive process hydrochloric acid helps to kill potentially harmfull microorganisms in food it is secreted from parital cells and it is a nonspecific immune response the stomach mixes the food w/ acids ta nd enzymes to make mixture called chyme that it is slowly released to the small intestine ▪ Small intestine — the small intestine is the site of where most of the reabsorption process happens food is further digested here with the help of the livier and pancreas the panceresase secretes digestive enzymes & an alkaline solution to kill hydrochloric acid the liver adds bile to make fats easier to digest digestion completes here and nutrients from food goes into the bloodstream this happens through villi projections of intestinal lining they each contain cappallaries that help nutrients pass ▪ Large intestine — aka colon recieves unabsorbed matieral from the small intestine primary function is to absorb water thats in the gi tract so that remaining food can become solid as it passes through the large intestine than it leaves as waste feces which are stored in the rectim until theyr ready to be eliminated