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FIU / Biological Science / BSC 2023 / What is digestive system?

What is digestive system?

What is digestive system?


School: Florida International University
Department: Biological Science
Course: Human Biology
Professor: Paul sharp
Term: Spring 2016
Tags: Human Bio and Bio
Cost: 50
Name: exam #3 study gui
Description: A summary of what's going to be on monday's exam, complete with pictures and probable test questions.
Uploaded: 04/02/2016
25 Pages 219 Views 12 Unlocks

4/2/16 3:04 PM

What is digestive system?


Digestive System: 

• Gastrointestinal tract: a continuous hollow tube extending from the mouth to the  anus. AKA: alimentary tract

• It's made up of the:

• Oral cavity: the mouth

o Hard palate: bony anterior part of the roof of the mouth

o Soft palate: only muscular portion at the back roof of the mouth

o Uvula: tissue tag hanging from the soft palate

o Salivary glands: glands associated with the mouth, they secrete saliva.  Saliva isn't secreted under the tongue

o Saliva: solution of water, mucus, salivary amylase, lysozyme, and  bicarbonate. (salivary amylase is the first enzyme that begins the  

What is the muscular tube for moving swallowed food from the pharynx?

Don't forget about the age old question of What is multidisciplinary?

digestion of starch--carbs)

o Tongue: occupies the floor of the mouth. Has 4 functions:

▪ Grips food

▪ Repositions food between teeth

▪ Mixes food with saliva (because the saliva has salivary  

amylase- an enzyme that starts to break down the  

carbohydrates in food we eat)

▪ Movements form the bolus (the mush of the food we are  

chewing that goes down when we swallow)

o Teeth:

▪ Lie in sockets in the gum covered margins of the maxilla and  


▪ 2 main divisions: crown and root

What is the last major portion of the digestive tract?

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▪ 32 teeth in adults

▪ Composed of:

???? Enamel: hard material composed of calcium compounds  

that cover the crown (the part of the tooth that is above  

the gum)

???? Dentin: thick layer of bone-like material beneath enamel

???? Pulp: inner tissue containing blood vessels and nerves

Don't forget about the age old question of What is the physical attractiveness stereotype?

▪ Problems:

???? Dental caries (cavity): hole in the tooth that results from  

acids produced by bacteria metabolizing sugar, the hole  

is close to the pulp when it starts to hurt the person.

???? Periodontitis: inflammation of the periodontal membrane  

that lines tooth sockets, this causes loss of bone and  

loosening of tooth

• Pharynx: the back of the throat

If you want to learn more check out Robbery is what type of crime?

• Esophagus

• Stomach

• Small intestine: absorbs nutrients

• Large intestine: absorbs water

• About 30 feet long in humans

• Accessory organs: the ones that aren't part of the tubing (tract) • 5 processes necessary so that the digestive process happens: 1. Ingestion: taking of food or liquid into the body through the mouth 2. Digestion: breaking down of large nutrient molecules into smaller molecules  that can be absorbed

▪ Mechanical digestion: cutting and mastication of food, peristalsis ▪ Chemical digestion: digestive enzymes hydrolyze macromolecules 3. Movement (mixing): food is passed from one organ to the next via peristalsis

4. Absorption: taking in of subunit molecules (like sugars, etc) by cells or  membranes. Happens in the small intestine

5. Elimination: process of expelling substances from the body via defecation  (pooping)

• Peristalsis: we don't have to think about our body digesting to make it happen, it  happens on its own.

• Reverse peristalsis: when there's something wrong with the food and makes us  vomit or expel it. If you want to learn more check out What is america's cold war policy?

• Smooth muscles have peristalsis, except the bladder which is a smooth muscle but  we have control over it (if we didn't we would pee our pants all the time)


• Pharynx:  

• Fancy word for throat

• Portion of the GI tract between the mouth and esophagus

• Serves as a passageway for food and also air on its way to trachea (the  trachea is parallel and in front of the esophagus)

• Esophagus: muscular tube for moving swallowed food from the pharynx to stomach • Swallowing: composed of a voluntary phase and involuntary phase (reflex action): • Soft palate moves back to close off nasal passage via uvula. This is so that  food doesn't get into the nasal passage.

• Epiglottis: covers the glottis, which is the opening to the larynx (voice box).  The epiglottis is like a lid on the glottis, it opens up either the path to the  trachea or the esophagus. The epiglottis doesn't work when we are  swallowing and laughing at the same time.

• Peristalsis: wavelike contractions that propel the bolus along the esophagus (smooth  muscles in the GI tract)

• Sphincters: muscle that surrounds a tube to open or close by relaxing or contracting.  • Lower gastroesophageal sphincter: marks the entrance of the esophagus to  stomach. It contracts to prevent the stomach acids from going up the esophagus  (although, when this happens it's called heartburn)

• Heartburn: lower gastroesophageal sphincter fails to open and allow food to go into  the stomach or it fails to close and the stomach acids go up the esophagus. • Stomach: a muscular sac that mixes food with gastric juices to form chyme which  enters the small intestine:

• 1L capacity, has a pH of 2 (same as a car battery)

• Stores food, doesn't absorb nutrients. It empties 2-6 hours

• Initiates digestion of proteins with enzyme pepsin

• Controls the movement of food into the small intestine

• Gastric juice: produced by gastric glands of the stomach, includes pepsin  mucus and hydrochloric acid (HCl)  

• The HCl destroys bad bacteria that enter in the food

• Chyme: thick semi-fluid food material that passes from stomach to the small  intestine

• Pyloric sphincter: regulates chyme entry into the small intestine

• The first place that chemical digestion happens is in the mouth, then in the stomach. • Pancreatic juice joins with the bile

• Small intestine:

• Long tube-like chamber of GI tract between stomach and large intestine • Contains enzymes secreted by pancreas and enters via duct in duodenum to  digest carbs, fats and proteins

• Receives bile produced by the liver and is stored by the gallbladder that is  released into the duodenum. The bile breaks things down into small globules  • Parts:

o Duodenum: first 10 inches of the small intestine

o Jejunum: 2nd part of the small intestine, 8 feet long

o Ileum: 3rd part of the small intestine, 12 feet long

• Nutrients are absorbed by the small intestine

• Villus: small fingerlike projections of the inner small intestine wall (mucosa) o Outer layer has cells that have microvilli (brush border)

o Blood capillaries and small lymphatic capillaries (lacteal) are present. •

• Lactose intolerance: inability to digest lactose because of an enzyme deficiency • These people do not have brush border enzyme lactase

• Symptoms:

o Diarrhea (due to fluid retention)

o Gas, bloating and cramps when bacteria break

o Down lactose anaerobically

• People that aren't lactose intolerant are mutants, what is supposed to happen  is that the only time that people are supposed to break down lactose was  when they were a baby so they could break down the mother's milk. But after  a mutation, the gene that stopped the breakdown of lactose after being a  baby was changed in some people so that people can breakdown lactose  their whole lives.

• Accessory organs:

• Pancreas: internal organ that produces digestive enzymes, it also produces  hormones insulin (helps lower sugar levels) and glucagon (helps elevate  sugar levels). Produces pancreatic juice that contains:

o Pancreatic amylase: enzyme in the pancreas that digests starch to  maltose

o Trypsin: protein-digesting enzyme  

o Lipase: fat-digesting enzyme secreted by the pancreas

• Bile: emulsification agent that is produced by the liver and stored in the gallbladder.  It splits one big globule into tiny droplets of fat that are easier to break down. • Test question: what is the enzyme responsible for breaking down proteins in the  stomach? Answer: pepsin.

• Accessory organs: they don't make up the tubing of the GI tract • Pancreas: produces pancreatic juice that has 3 important enzymes:  pancreatic amylase, trypsin and lipase. The pancreatic juice is dispersed into  the duodenum in the small intestine.


o Glucose is stored in the human body as glycogen

o Plants store glucose as starch

o Diabetes:

▪ Type 1: pancreas doesn't produce enough amounts of insulin  

(so the glucose can't get into the cells), typically diagnosed  

before 15 years of age

▪ Type 2: pancreas doesn't make enough insulin or the body's  

cells are insulin resistant, typically diagnosed after 40 years of  


• Liver: dark red internal organ that:

o Detoxifies blood: hepatic portal vein brings food to liver from the GI  tract capillaries

o Stores glucose as glycogen, iron, vitamins A,D,E,K and B12

o Produces plasma protein and urea (primary nitrogenous waste product  that results from breaking down amino acids)

o Produces bile (that is stored in the gallbladder)

o Regulates cholesterol:  

▪ Good cholesterol: HDL

▪ Bad cholesterol: LDL

o Liver diseases:

▪ Jaundice: skin turns yellowish from abnormal bilirubin (bile  

pigment) in blood meaning the liver is malfunctioning

▪ Hepatitis: inflammation of the liver, often caused by the Hepatitis  B virus

▪ Cirrhosis: chronic irreversible injury to the liver tissue, caused by  excessive alcohol consumption over long periods of time and  

Hepatitis C virus.

• Large intestine: last major portion of the digestive tract that extends from the small  intestine to the anus and  

• Contains:

o Cecum: the vermiform appendix is at the end of the cecum, the cecum  is a blind pouch at the beginning

o Vermiform appendix: small tubular appendage that extends out from  the cecum that aids in fighting infections. If the appendix is infected it is  removed because the infections it fights might explode into the body

o Colon: major portion of the large intestine, consists of the ascending  colon, transverse colon, descending colon and sigmoid colon

o Rectum: terminal end of the digestive tube, last 20 cm of the large  intestine, stores feces

o Anus: outlet of the digestive system, where excretion occurs

• Approx. 5 feet long

• Main function: absorb water

• DOES NOT absorb nutrients, only vitamin K and B complex

The Skeletal System: 

• System of protection and support

• The skeleton is composed of bones, cartilages (prevents the bones from rubbing),  joints and ligaments (connect bones together)

• Skeleton starts forming when the embryo is 6 weeks old

• 206 named bones in the skeletal system

• Make up 20% of body weight

• Tendon: connects bone to muscle

• Functions:

• Supports the body

• Protects soft body parts (heart)

• Produces blood cells

• Stores minerals (calcium and phosphate, these are what human bones are  made of) and fats (fat is stored in the middle of the bone in yellow bone  marrow)

• Allows flexible body movement (along with the muscles)

• Parts of the skeleton:

• Axial skeleton: main axis, forms the long axis of the boxy and includes the  bones of the skull vertebral column and the rib cage

• Appendicular skeleton: consists of bones of the limbs

• Cartilage: white flexible semi opaque connective tissue, chondrocytes (exocytosis of  matrix that makes the cartilage) are the mature cell form of cartilage, has no nerves  or blood vessels, it prevents bones from rubbing each other. Takes long to repair

• Ligament: band of fibrous tissue that connects bone to bone, has cells called  fibroblasts

• Tendons: cord of fibrous tissue attaching muscle to bone, has cells called fibroblasts • Every week we recycle 5 to 7% of our bone mass

• Chemical composition of bones:

• Organic components: osteoblasts, osteocytes and osteoclasts. They are  composed of living tissue.

o Osteoblast: they form the bone by exocytosis of matrix and they  promote the deposition of calcium salts into the matrix

o Osteocytes: maintain the structure of the bone, they are mature bone  cells derived from osteoblasts

o Osteoclasts: large cells that reabsorb or break down bone matrix, they  assist in returning calcium and phosphate to the blood. These acts  when there is a weak bone. Also these are the cells that allow the body  to grab calcium from bones if it needs it

• Inorganic components: hydroxyapatites (mineral salts), largely composed of  calcium phosphate.

• When we don't ingest enough calcium, the body needs it so bad that it grabs it from  the bones.

• Ossification: formation of bone

• Structure of a long bone:

• Compact bone: highly organized and composed of tubular units called  osteons (like coffee stirs) These have osteocytes that occupy small cavities  (lacunae). Canalicuni connect lacunae to one another and to the central  canal. The central canal contains small blood vessels and nerve fibers.

• Spongy bone: has an unorganized appearance. Its composed of numerous  struts or thin plates (trabeculae) separated by uneven spaces, these spaces  are often filled with red bone marrow

• Intramembranous ossification: flat bones that develop between sheets of embryonic  fibrous connective tissue membranes e.g. skull clavicles and mandible • Endochondrial ossification: happens in long bones: arms and legs: occurs at 6  weeks into the embryo. First a cartilage model is formed, then it grows, then there's  a development of primary ossification center (spongy bone) (starts to provide  resources for the bone to form), then the medullary )marrow) cavity develops, then  the secondary ossification center (happens after the baby is born), lastly the  formation of articular cartilage and epiphyseal plate (cartilage lining). • When do our bones stop growing: Girls on average 18 and boys on average 21. • Muscle types;

1. Smooth muscle: consists of spindle shaped, nonstriated muscle cells: they  are located in the walls of hollow internal organs and blood vessels, has a  single nucleus in cell, involuntary muscle that is slow to react, does not fatigue  easily.

2. Cardiac muscle: specialized muscle lf the heart, striated (areas of dark light  dark light dark light),has 1 or 2 nuclei per cell, cardiac cells interlock at  intercalated disks, involuntary muscle

3. Skeletal muscle: composed of cylindrical multinucleate cells with obvious  striations, consists of muscles attached to the body's skeleton, voluntary  muscle.

• Types of muscle:

• Functions of Skeletal Muscle:

1. Support: allows us to stand erect

2. Movement of bones and other body structures

3. Maintenance of constant body temp

4. Movement of fluids in the cardio and lymphatic systems

5. Protection of internal organs and stabilization of joints:

o Muscles pad the bones

o Muscular wall in abdominal region protect internal organs

o Muscle tendons

• How do muscles move bones?

• They work in pairs:

o Each muscle is concerned with the movement of only 1 bone

o When muscles contract they shorten

o Muscles can only pull, not push

• Origin: the end of a muscle attached to a stationary bone  

• Insertion: the end of a muscle attached to a movable bone

o When muscle contracts it pulls on tendons at its insertion and the bone  moves

o The nervous system stimulates an appropriate group of muscles o EG: the prime mover and synergists

• Antagonist: muscle that acts opposite another muscle (eg: bicep and triceps)  photo

• Structures of muscle cells:

• Sarcolemma: plasma membrane of a muscle fiber, forms the tubules of the T  system. Encases hundreds to thousands of myofibrils

• T (transverse) tubules: membranous channel that extends inward toward  sarcoplasmic reticulum

• Sarcoplasmic reticulum: smooth endoplasmic reticulum of muscle cells.  Surrounds myofibrils and stores calcium ions

• Myofibril: rod-like bundle of contractile filaments found in muscle cells. They  are made out of repeating units called sarcomere (they lie between z lines, as  seen in the picture)

• Hierarchical order of a muscle:


1. Fascicle: a bundle of muscle fibers surrounded by connective tissue 2. Muscle fibers (Myofiber): muscle cells

3. Myofibrils: contractile portion of muscle fiber (cells) that contains a linear  arrangement of sarcomeres

o They run the entire length of the muscle (so they are as long as your  bicep or triceps etc)

o They are composed of even smaller myofilaments

4. Myofilament: responsible for the actual contraction of muscles.  

o Sliding filament model: muscle contraction based on the movement of  actin fibers in relation to myosin filaments.

o Two types:

1. Actin: makes up thin filaments in myofibrils.

2. Myosin: one of the contractile proteins of muscle. Makes up  

thick filaments in myofibrils. They have little arms going out of  

the sides and at the end of each arm there's a myosin head, and  

these are like tugging and pulling the muscle in opposite  

direction to contract the muscle. Picture.

▪ In the picture: the myosin is the yellow space in the middle, the  actin is the pinkish part in the edges and the dark part is made  

up of the mix of both.

5. Sarcomeres: the smallest contractile portion of muscle that is arranged  linearly within myofibril and extends from one z line to the next z line.

• Neuromuscular junction:  

• Where the axon of a motor neuron is attached to a muscle.  

• The axon terminal communicates with the muscle through neurotransmitters.  • The muscle has ligand gated channels that allow the sodium to rush in and  cause the action potential to move along the muscle until it hits the  sarcoplasmic reticulum which releases calcium.  

• There's tropomyosin, that's like a rope that covers the myosin binding sites  (what causes the myosin to grab onto the actin and contract the muscle).  • Attached to the tropomyosin are troponin, and these are turned on by calcium,  when this happens it lifts the tropomyosin up and allows the myosin to bind to  the actin and contract the muscle.

• Rigor mortis: when a person or animal dies and the limbs stiffen out because of a  chemical change in the muscles.

Immunity and Lymphatic system:

• Lymph organs: organ of lymphatic system other than lymphatic vessels

1. Primary: red bone marrow and thymus gland

2. Secondary: lymph nodes, spleen, tonsils, appendix and Peyer's patches • Red bone marrow: produces red blood cells, like:

• Leukocytes (allergies, especially pollen): neutrophils (phagocytosis),  eosinophils and basophils (both degranulate, throw chemicals at things that  shouldn't be in the body). These are like the "common people in the castle"

• Lymphocytes: B cells (mature in bone marrow and produce antibodies), T  cells (mature in thymus), natural killer cells. These are like the "military, king's  guard".

• Thymus: involved in the maturation of T cells, only about 5% pass autoreactivity test.  Located between the trachea and the sternum superior to the heart. • Spleen: stores and filters blood; macrophages phagocytose pathogens and debris.  Largest lymphatic organ

• Lymph nodes: mass of lymphatic tissue located along the course of a lymphatic  vessel, macrophages phagocytose pathogens and debris.

• Tonsils: patches of lymphatic tissue, first to encounter pathogens • Peyer's patches: lymphatic tissue located within the appendix and encounters  pathogens.

• Autoimmune disease: when your own body attacks itself. The thymus is responsible  so that this doesn't happen.

• One of the functions of the lymphatic vessel is to pick up what the circulatory system  leaks out:

Immune system:

• Functional system whose components attack foreign substances or prevent their  entry to the body

1. Innate immunity: skin, mucous membranes. A mechanism of defense that doesn't  depend on prior exposure to the invader, nonspecific (broad) (the skin protects  against everything). Immediate.

• First line of defense:

o Skin: layer of protection associated with the innate immunity system.  Like the castle wall. Oil and sweat glands give skin surface pH of 3-5,  sweat contains lysozyme (digests bacterial cell wall), normal flora  

include non-pathogenic bacteria and fungi, epidermis 10-30 cells thick and dermis 15-40 times thicker.

o Mucous membranes:  

1. Digestive tract: saliva contains lysozyme (also found in tears),  

acidic environment of stomach pH of 1.5-3.5, digestive enzymes  

in intestine, nonpathogenic normal flora, vomiting and diarrhea  

may expel pathogens.  

2. Respiratory tract: pathogens trapped by mucus in bronchi and  

bronchioles, ciliated epithelial cells sweep mucus toward the  

glottis, coughing and sneezing expels pathogens.

3. Urogenital tract: vaginal secretions viscous and acidic,  

secretions promote growth of normal flora, acidic urine of both  

sexes may wash out pathogens.

2. Adaptive (acquired) immunity: specific to the particular non-self material, requires  time for development, occurs more quickly and vigorously on secondary response.

• Second line of defense: phagocytes, inflammation, complement and  interferon, chemical signals:

o Recognize a wide spectrum of pathogens without a need for prior  exposure

o Key players include neutrophils, monocytes that become macrophages o These cells phagocytose pathogens and trigger the release of  cytokines (chemical signals, protein hormones that let other immune  system "soldiers" or cells where the problem is)

o Results in inflammation and specific immune responses

o Inflammation: occurs over seconds, minutes, hours and days ▪ Histamine: chemical that dilates blood vessels

▪ Bradykinins: make the spaces that make the blood vessels  leaky even larger so there is more leakage

▪ Prostaglandins: responsible for the pain (eg: sunburnt skin pain) 1. Dilation of blood vessels increases blood flow at site (RED &  WARM)

2. Increased permeability of capillaries causing edema (tissue  SWELLING). This allows the cells to move to the site of the  

harm quicker.

3. Tissue swelling puts pressure on nerve endings (PAIN and  potential loss of function)

4. Macrophages and neutrophils release cytokine tumor necrosis  factor (TNF) which acts on hypothalamus to raise the body temp  (fever)

5. Cell death (necrosis) always occurs to some degree during  inflammation

o Complement: 30 proteins that are produced by the liver. They circulate  freely in blood plasma. When activated, one forms a domino effect on  another causing a cascade of events that form a membrane attack  complex (MAC) that form pores in pathogens that have lipid membrane  to induce lysis (causes the bad bacteria to explode by making holes in  its membrane)


o Interferon: antiviral agent produced by an infected cell that blocks  infection of an uninfected cell (degrades RNA and blocks protein  production). It works especially with virus. Type of cytokine. o

o Cytokines: protein hormones used by immune cells to communicate.  Can affect same cells that produce them, cells nearby or cells distant in  body. EG: interferon.



• Third line of defense: ADAPTIVE IMMUNITY

o Important aspects of the immune response:

1. Non-self recognition: ability to distinguish self-antigens from  non-self

a. Antigen: foreign substance that stimulates and immune  

response. EG: dust, pollen

b. Antibody: protein produced in response to the presence  

of an antigen

2. Antigen-specific: recognizes and is directed against specific  antigens

3. Systemic response: immunity is not restricted to initial infection  site

4. "Memory": recognizes and mounts stronger attack on previously  encountered pathogens.  

o Major histocompatibility complex (MHC): cell surface glycoproteins,  polymorphic. Think of them as flag poles on the surface of cells. Only T  cells can decipher them.

▪ MHC class 1 protein: found in eukaryotes (cells that have  

nucleus), has cytotoxic T cells (CD8) respond to endogenous  antigen (generated inside the cell) bound to MHC class 1  

protein. The CD8 is the only cell that understands the signal.  

When the CD8 connects with an infected cell and realizes that  something is wrong, it produces cytokines that communicate  

with the infected cell through its own cytokines which cause the  CD8 to clone itself and attack the infected cell until it causes  

apoptosis (to explode)

▪ MHC class 2 protein:

???? Found only on professional antigen presenting cells like  Macrophages and B cells

???? Helper T cells (CD4) respond to exogenous antigen  

(comes from outside the cell) bound to MHC class 2  


???? When bacteria is engulfed by macrophages, the Helper T  cell connects with the macrophages, then clones itself,  

and then has 2 choices: to produce a humoral response  (communicates with a B cell that clones and the "general"  (CD4) signals them to fire their arrows towards the  

infected cell) or a cellular response (it "juices up" the  

macrophage and destroys the bacteria)

o Two overlapping arms of immunity:

▪ Cell-mediated immunity: (like hand to hand combat), associated  with cell surfaces, T-cell receptors that are unable to see free  


???? T cells: 2 main types that include CD8 (directly attack  

cells that carry specific antigens) and CD4 (regulate  

immune responses of other cells, they are like the  

"general" during battle)

• Produced in red bone marrow, they migrate to the  

thymus to mature and be selected

• T cell receptors recognize antigen presented on  

self MHC molecules

▪ Humoral immunity: (like archers shooting arrows), based on  

antibodies on cell surfaces and in body fluids (blood, lymph,  


???? B cells: bind to specific antigen with its antibody (B cell  

receptor) and also serve as antigen presenting cell to  

Helper T cells. They are produced in red bone marrow.  

Immunoglobulin synthesis happens in bone marrow.  

Tested for accuracy in red bone marrow as well. Types:

• Plasma B cells: are large B cells that have been  

exposed to antigen, they produce and secrete  

large amounts of antibodies, are short lived cells  

that undergo apoptosis

• Memory B cells: are specific to the antigen  

encountered, they live for a long time and can  

respond quickly following a second exposure to  

the same antigen.

• HIV (Human immunodeficiency virus): a retrovirus that attacks the body's immune  system, causes AIDS.

• HIV mounts direct attack on TH cells by binding to CD4 proteins on cell  surface

• HIV kills TH cells faster than they can proliferate over time

• When CD4 and T cell numbers decline bellow 200 cells per microlitre of  blood, the cell mediated immunity is lost.

Respiratory System: 

• Ensures oxygen enters body while carbon dioxide leaves body •

• Composed of:  

• Upper respiratory tract: conditions air as it enters the body.  

o Nasal cavity: air is humidified, heated. Has flaps of tissue. Has large  hairs that filter air and mucus membranes that produce mucus.

Capillaries of sub-mucosa warm and moisten air. Tear (lacrimal)  

glands drain into the nasal cavity (when we cry we get runny noses  because the tears that don't drip out of our eyes go to our nose, this  helps clean the nasal cavity.

o Pharynx: place where pathways for air and food cross. Connects nasal  and oral cavities to the larynx,

▪ Tonsils: primary defense during breathing

▪ Epiglottis: covers the entrance to the larynx. Prevents food from  going to the larynx. Like the doors to the larynx (they open and  


▪ Uvula: tab of tissue at the back of throat it contracts when  

touches by food and prevents food from going into the nasal  


o Glottis: entrance to the larynx (covered by the epiglottis). Like the  doorway to the larynx.

o Larynx: voice box. Cartilaginous organ between pharynx and trachea. ▪ Vocal cords: fold of tissue that vibrates to create vocal sounds]

▪ Glottis: opens air flow in the larynx

• Lower respiratory tract: allows oxygen to enter the blood and waste gases to  leave blood.  

o Trachea: windpipe, passage of air to bronchi. In front of the esophagus  so that when we eat something big there's room for the trachea to  

move and not collapse. Consists of connective tissue, smooth muscle  and cartilaginous rings. Has mucosal membrane that produces mucus  (from goblet cells) and is lines with cilia that push the mucus upward. o Bronchus/Bronchi (plural): passage of air to lungs  

o Bronchioles: passage of air to alveoli

o Lungs: contain alveoli (air sacs lined with surfactant which reduces  water tension) that carry out the gas exchange. The right lung has 3  lobes and the left one has 2 because of the cardiac notch.

o Diaphragm: skeletal muscle, functions in ventilation. What separates  the abdominal cavity from the thoracic cavity. When we inhale it  

pushes down because the lungs expand and when we exhale it pushes  up because the lungs compress.

• The groups of alveoli are called lobules.

• The pulmonary artery takes deoxygenated blood to the capillaries of the alveoli and  then the pulmonary vein takes oxygenated blood from the capillaries of the alveoli to  the heart.

• Air (oxygen) gets into the capillaries that go to the alveoli by diffusion. It goes from a  high concentration in the capillaries to a lower concentration inside the alveoli. • External respiration: pulmonary gas exchange. CO2 from the capillaries is  exchanged for O2 by the alveoli.  

• Internal respiration: systemic gas exchange by systemic tissue cells. Oxygen goes to  tissue cells in organs and is exchanged for CO2 which goes into the capillaries •

• Our cells produce CO2 when they do cellular respiration and when they separate  glucose molecules. This is the CO2 that will be exchanged for the O2. It's also  exchanged through diffusion

• The right side of the heart pumps deoxygenated blood.

• If we didn't have a diaphragm we could not breathe

• Valsalva maneuver: forceful attempt to exhale against a closed airway, like pinching  the nose shut and closing the mouth while pressing out air as if blowing a balloon.  This is done to equalize air pressure.

• Spirometer: measures the volume of air that is inspired and expired by the lungs. • Total capacity of the lungs is 5800 ml.

• Tidal volume: normal, shallow breaths. They amount 5000 ml approx. • There's always some air left in the lungs because if we get rid of all of the air, then  the lungs collapse. This air is called residual volume. When someone "knocks the  wind out of you", you can't breathe, you lost some of the residual volume.

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