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Chapter 20:Tissues & Organ Systems

The Importance of HomeostasisThe maintenance of a relatively constantinternal environment, i.e., homeostasis, isessential for life.

Temperature

Cellular conditions that need to be maintained within a narrow range include:

pH

concentrations of: minerals, nutrients, wastes

Negative FeedbackHomeostasis is largely maintained by what isknown as Negative Feedback:

• counteracting a change in body state torestore the original state

• sweating to cool an overheated body

• releasing insulin to lower blood sugar

**various sensory systems in the body detectchanges and trigger negative feedback responses**

e.g.

• accelerated breathing, pulse to increase oxygen

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Organization of the Animal Body

Cells Tissues Organs Organ Systems

The 4 Basic Tissue Types

Epithelial Tissue

Connective Tissue

Muscle Tissue

Nerve Tissue

All tissues in the animal body fall into one of4 basic tissue types:

Epithelial TissueSheets of cells that line body surfaces, cavities:

skin; digestive, urinary,reproductive tracts;vessels; glands

Epithelial cells come in 3 basic shapes…

• cuboidal (cube-shaped)• squamos (flattened)

• columnar (elongated)…and in single or multiple layers:

simple or stratified epith.

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simple squamous epithelium (lung)

simple cuboidalepithelium (kidney)

simple columnar epithelium (intestine)

stratified squamous epithelium(lining the esophagus)

dead cells

rapidly dividing

cells

stratified squamous epithelium(human skin)

Col

oriz

ed S

EM

Examples of Epithelial Tissue

Connective TissueTissue that supports, binds, “fills” or provides structure.

Connective Tissue (CT) comes in 3 basic types:Loose CT – underlies epithelium, loosely woven fibers,

“gel-like”

Fibrous or Dense CT – densely packed fibers as in tendons & ligaments

Specialized CT – bone, cartilage, blood & lymph,adipose (fat) tissue

• contains few cells, mostly extracellular matrix (ECM)

Cartilage-formingcells

Matrix

cartilage (end of a bone)

Centralcanal

Matrix

Bone-formingcells

bone

bloodloose connective tissue

(under the skin)

Collagenfibers

Cellnucleus

fibrous connective tissue (tendon) White blood

cells

Red bloodcell

Plasma

adipose tissue

Fatdroplets

Examples of Connective Tissue

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Unit ofmusclecontraction Muscle

fiber

Nucleus

skeletal muscle

Nucleus

Musclefiber

Junction betweentwo cells

Muscle fiberNucleus

smooth muscle

cardiac muscle

Muscle TissueMade of cells that contract, comes in 3 types:

Skeletal Muscle (striated, voluntary – moves skeleton)Cardiac Muscle (striated, involuntary – heartbeat)Smooth Muscle (unstriated, involuntary – visceral org., vessels)

Nerve TissueTissue that transmits electrical signals.

Contains 2 basic cell types:Neurons – cells that generate, transmit electrical signals

Glial cells (glia)– metabolic support, insulation for neurons

neuron

Organs and Organ Systems

Organ systems = multiple organs that work together to perform a common function

• each tissue and organ has a distinct role

• skin, nails, hair each have different roles

e.g. – Integumentary System (skin, nails, etc)

• each contains multiple tissues (epithelium, connective tissue, muscle, nerve) with diff. roles

Organs = multiple tissues that comprise aphysically & functionally distinct structure

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Organs are made of all Tissue TypesSmall intestine

(cut open)

Lumen

epithelial tissue(columnar epithelium)

connective tissue

smooth muscletissue (2 layers)

connective tissueepithelial tissue

Lumen

10 Major Organ Systems

The Circulatory System(blood & vessels, heart)• nutrient & waste transport• temperature control• pH balance

Lymphatic/Immune System(lymph & vessels, lymphocytes)

• fluid balance, transport• fat transport• immune responses

• movement of cells, hormones

(11 if you count the Integumentary System)

The Endocrine System(endocrine glands)• hormone production• physiological control

The Nervous System(brain, spinal cord, nerves)• internal, external sensation• behavioral control• physiological control

Organ Systems cont’d…

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The Digestive System(esophagus, stomach, liver, intestines, pancreas)• food breakdown, absorption• waste disposal

The Urinary System(kidneys, bladder)• blood-borne waste disposal• salt & water homeostasis

The Respiratory System(pharynx, trachea, lungs)• gas exchange• pH balance

The Muscular System(all 3 muscle types)• movement of skeleton• movement in hollow organs• heartbeat

The Skeletal System(bones, cartilage, tendons…)• structural support• blood production• calcium, phosph. storage

The Reproductive System(ovaries, uterus, testes…)• gamete, production• hormone production• nurturing offspring

Key Terms for Chapter 20

Relevant Review Questions: 2-14

• connective tissue – loose, fibrous, specialized

• homeostasis

• epithelium – squamous, cuboidal, columnarsimple & stratified

• skeletal, smooth & cardiac muscle

• neurons & glial cells

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Chapters 21-23, 25:Organ Systems of the Body

1. Circulatory System

2. Respiratory System

3. Digestive System

4. Urinary System

1. The Circulatory System

Organs of the Circulatory SystemHeart

Blood vessels

Blood

Roles of the Circulatory System• deliver O2, remove CO2

• transport nutrients, wastes, hormones

• regulate temperature & pH

• immune protection (antibodies, white blood cells)

pumps the blood

veins, arteries, capillaries

red & white blood cells, blood plasma

(we’ll also look at lymph and lymphatic vessels)

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Vertebrate CirculationFish have a 2 chambered heart Reptiles &

amphibianshave a 3 chamberedheart

Mammals &birds have a heart with 4 chambers

rightatrium

leftatrium

semilunarvalve

semilunarvalve

atrioventricular(AV) valve

atrioventricular(AV) valve

rightventricle

leftventricle

The Human Heart

The Cardiac Cycle

oxygenated vs deoxygenated

1 2 3

1. Atria contract, forcing blood from right atrium & left atrium into ventricles

2. Ventricles contract, forcing blood into aorta(fr. LV) and pulmonary artery (fr. RV)

3. Atria & ventricles relax (diastole), cycle repeats…

systole

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1

2 7

8

9

2

3

4

5

6

4 10

3

9

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superiorvena cava

capillaries ofhead, chest, and arms

pulmonaryartery

capillariesof left lung

pulmonary vein

aorta

left atriumleft ventricle

aorta

capillaries ofabdominal region

and legs

inferiorvena cava

right ventricle

right atrium

pulmonary vein

capillariesof right lung

pulmonaryartery

Blood Circulation

1 2 3 4

Pacemaker(SA node) AV node

Specializedmuscle fibers

Apex

Rightventricle

ECG

Control of the HeartbeatThe synchronous contraction of cardiac muscle cells is controlled by the sinoatrial (SA) & atrioventricular (AV) nodes.

• ea beat starts at the SA node, stimulates AV node (delayed)

Oxygen TransportOxygen is transported by redblood cells (RBCs)

• vast majority of blood cells (~99%) are RBCs

• aka erythrocytes

• each hemoglobinmolecule binds 8 O2

• don’t have a nucleus!

• vast majority of proteinin RBCs is hemoglobin

Oxygen binds to hemoglobin in RBCs

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Other Blood CellsBlood also contains:

• essential for blood clotting

• collective term for allcells of immune system

• B cells, T cells, monocytes, neutrophils…

Platelets

• “pinch off” from cells inbone marrow calledmegakaryocytes

White Blood Cells

Blood VasculatureArteries, arterioles:

• conduct blood flow awayfrom the heart

• usually oxygenated blood

Veins, venules:• conduct blood flow toward

the heart• usu. deoxygenated blood

Capillaries:• smallest vessels• where “exchange” occurs

CapillariesUnlike larger vessels, capillary walls are only 1 cellthick, barely wide enough for RBCs to pass through

• allows diffusion of gases,nutrients, wastes betweenblood & tissues

• some fluid (plasma)“leaks out” as well

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The Lymphatic SystemA vascular system distinct from the circulatory system • conducts fluid “leaked” from

the blood called lymph

• lymph is filtered throughstructures called lymph nodes

• full of immune cells, important part of the immune response

• also transports fats fromdigestion in small intestine

• returned to blood at vena cava

Lymphatic Vessels

Fluid leaked fromcapillaries is takenup by “lymphcapillaries”

• lymph is conducted intolarger lymphatic vessels

• lymph passes throughlymph nodes before being“dumped” into the blood at the vena cava

2. The Respiratory System

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The Respiratory System

• facilitate O2 uptake, waste CO2 removal

Respiratory System function :

Respiratory System OrgansNasal Cavity

Pharynx

Larynx

warms & moistens air

passage for air, food/water

vocal chords; where air, food separate

Epiglottis blocks airway when swallowing

Trachea connects airway to lungs

Lungs site of gas exchange

Diaphragm muscle used for “inhaling”

Rib cageexpands asrib musclescontract

airinhaled

Rib cage getssmaller asrib musclesrelax

airexhaled

lung

diaphragm

Diaphragm relaxes(moves up)

Diaphragm contracts(moves down)

Inhalation Exhalation

Inhalation & Exhalation

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The LungsThe bronchi of the lungs branch into smaller andsmaller bronchioles which terminate in alveoli.

• alveoli are thesites of gasexchange

• arrangementmaximizes thesurface area forgas exchange

Gas Exchange in the AlveoliO2 and CO2 simply diffuse from higher to lowerconcentration across the capillary, alveolar epithelia

• O2 is moreconcentrated in the lungs than inthe blood

• CO2 is moreconcentrated in the blood than inthe lungs

*situation reversed in body tissues*

Summary of Gas Exchange

lungs

tissues

Deoxygenated blood from tissues returns to the right atrium &ventricle of the heart which pumps it to the lungs.

In the alveoli of the lungs bloodis oxygenated and flows backto the left atrium & ventricleof the heart, from which it is pumped back to the body.

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3. The Digestive System

Digestive System Functions1) Digest food and absorb nutrients

• mechanical breakdown

2) Waste removal

• physical breakdown of food into smaller particles

• chemical digestion• breakdown of large molecules (polymers) into

smaller ones (monomers)

• absorption• transfer of digested material into blood & lymph

• undigested material & waste from liver

Organs of the Digestive System

• mouthDigestive Tract

• pharynx

• esophagus

• stomach

• small intestine

• large intestine

Accessory Organs • liver

• gall bladder

• pancreas

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Bolus offood

Muscles relax,allowing passagewayto open

Stomach

Musclescontract,constrictingpassagewayand pushingbolus down

Muscles contract

Muscles relax

Muscles contract

Musclesrelax

Early DigestionMouth & Pharynx • chewing (mastication) of food,

mixing with saliva• swallowing of food bolus

Esophagus • muscular tube conducting foodbolus from pharynx to stomach

Stomach • mechanically “churns” food• adds pepsin (digests protein) and HCl (kills microbes, activates pepsin)

• starch digestion via amylase

Completion of DigestionSmall Intestine

• 3 sections: duodenum > jejunum > ileum

Pancreas • secretes “pancreatic juice”(enzymes, bicarbonate)to complete digestion

Liver & Gall Bladder • bile from liver added toduodenum via gall bladder

• bile helps emulsify fatsfor better digestion

• digestion is completed in the duodenum• absorption of nutrients

musclelayers

largecircular folds

villinutrient

absorption

Veinwith blooden route to

the liver

lumen

Lumen of Intestinenutrient

absorption

epithelialcells

bloodcapillaries

lymphvessel

Villi

nutrient absorption into epithelial cells

microvilli

Epithelial Cells

aminoacids and

sugars

fattyacids andglycerol

blood

fats

lymph

Intestinal Wall

Nutrient AbsorptionNutrients are absorbed throughout small intestine.

• nutrients are transferred to the blood or the lymph (fats)

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Folds, Villi & Microvilli

Folds in the intestinal wall as well as villi & microvilligreatly increase surface area for nutrient absorption.

• villi are multicellular finger-like projections

• microvilli are projections on individual cells

Waste RemovalLarge Intestine: cecum > colon > rectum

• absorption of water, minerals, vitamins

• compaction, elimination of waste (undigested material, fiber, bacteria)

• houses a variety of beneficial bacteria (aka “probiotics”)

***bacteria need to be kept OUT of small intestine***

Largeintestine(colon)

Sphincter

Endof smallintestine

AppendixCecum

Anus

Rectum

Smallintestine

Nutrientflow

4. The Urinary System

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The Urinary System

• removal of waste,excess in blood

• conduct urine fromkidneys to bladder

• holds, expels urine

• conducts urinefrom bladder “out”

Kidneys

Ureters

Bladder

Urethra

The KidneyOrganized into functional unitscalled nephrons

Nephron Structureglomerulus

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Filtration in the Kidney1. Dissolved substances leave the blood in the

glomerulus, enter glomerular capsule > tubule

glomerulus

tubule

2. Needed H20, salt, nutrients reabsorbed from tubule

*maintains pH,salt & water

homeostasis*

3. Additional wastes added to urine

1 2

3

4. H2O reclaimed

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Water & Salt HomeostasisAntidiuretic Hormone (ADH) regulateswater resorption in the kidneys:

• released by the pituitary gland• “sensors” in brain and heart regulate ADH release

• increases permeability of kidney tubules,greater water resorption

Aldosterone released from the adrenalcortex regulates “salt” levels:

• stimulates retention of sodium ions (Na+), excretion of potassium (K+) in kidneys

Key Terms for Chapters 21-23 & 25

• hemoglobin, white blood cells, platelets

• atrium, ventricle, aorta, vena cava

• sinoatrial, atrioventricular nodes

• arteries, arterioles, veins, venules, capillaries• lymph, lymph nodes

• pharynx, larynx, epiglottis, diaphragm, alveoli• villi, microvilli, • nephron, glomerulus, tubule

Relevant Review Questions: Ch. 21: 1 Ch. 22: 1, 2, 5, 7

Ch. 23: 1, 2, 4, 5 Ch. 25: 2, 4