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Tissues:
The Living Fabric
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Tissues: The Living Fabric Unit Front Page
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Tissue: The Living Fabric This checklist will serve as your “study guide” to help you prepare for your exams. At the end of this unit, you will: □ Identify the four main types of tissues and overall characteristics. How are tissues classified? Explain the function of tissues based on their structure. □ Explain the anatomical features that all epithelial tissues share and describe the function of these structures. □ Name, classify, and describe the various types of epithelial tissue. Justify the chief functions of each type of epithelia based on its structure and classification. Infer where these types of epithelia are located in the body based on their functions. □ Define glands and differentiate between endocrine and exocrine glands. Give examples of each. □ Explain the classification system for glands – for example, how do you name a gland based on the duct and gland shape? Give examples of glands in each class. □ What type of epithelial tissue are glands? Explain the different modes of secretion. □ Explain the structures/features that all connective tissues have in common and describe the function of these structures. □ Classify and identify the types of connective tissues found in the body and describe their characteristics. □ Differentiate the three different types of fibers found in connective tissue. Describe how the arrangement and location of these fibers in various connective tissues affect their function. □ Justify the chief functions of each type of connective tissue. □ What type of epithelial tissues are “mucous membranes?” Relate the production of mucus to the endomembrane system. □ Outline the process of tissue repair of a superficial wound. □ Design and Engineer a tissue-like material to replace a broken bone and complete a cost analysis to determine financial constraints. Roots, Prefixes and Suffixes I will understand and recognize in words are: □ ap-, areola-, basal-, blast-, chyme-, endo-, epi-, holo-, hormon-, hyal-, lamina-, mero-, meso-, retic-, sero-, squam-, strat-, epithet-, pseudo□ –crine, -glia,
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Special Characteristics of Epithelium
Description
Function
Location
Simple Squamous Epithelia
Simple Cuboidal Epithelia
Simple Columnar Epithelia
PseudoStratified Columnar Epithelia Stratified Squamous Epithelia
Transitional Epithelia
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Reading Guide: Chapter 4a Tissues: The Living Fabric Tissue Intro, Epithelia, and Glandular Cells Instructions: The specific instructions for various activities in the reading guides can be found in your reference pages you saved in your backpack on edmodo. Refer to these pages carefully, as you will be completing reading guides all throughout this year. Since reading guides are a type of formative assessment, they are graded on completion, follow-through with guidelines, and quality. 1. Read pgs. 118 – 119: Introduction, Preparing Human Tissue for Microscopy and Epithelial Tissue. On page 156 of your intNB, write a GIST on the Special Characteristics of Epithelium. On the image to your left, page 154 of your intNB, label the apical surface and the basal surface. Color the connective tissue yellow, the basement membrane blue, and the cells pink. Color the cell nuclei red. Use the same color scheme for coloring exercises of other tissues in this reading guide. 2. Read pages 119 – 124: Classification of Epithelia Using the same color schemes as in the exercise above, color the different classes of epithelial cells on the three-tab foldable that your teacher will give you. Cut out the tabs and glue or tape the foldable onto page 158 of your intNB using the left strip of the foldable. You will fill in notes about these cells during lecture. On the table to your left on page 154, fill in information on each epithelial cell type’s description, function, and location. Figure 4.2 in your textbook will help you. Take NOTES. Don’t use full sentences. 3. Read pages 124 – 126: Glandular Epithelia. Write a GIST about glandular Epithelia on page 157.
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Reading Guide Chapter 4a: Tissue Intro, Epithelia, and Glands GIST 1
Special Characteristics of Epithelium
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Reading Guide Chapter 4a: Tissue Intro, Epithelia, and Glands GIST 2
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Three-Tab Foldable of Epithelial Classification
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Intentionally Left Blank
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Identify each of the following tissues:
Tissue Type: ____________________________
Tissue Type: ____________________________
Tissue Type: ____________________________
Tissue Type: ____________________________
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Date_______________
Chapter 4: Tissues Introduction, Epithelial Tissue Classification, Glands
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Label the following epithelial tissue samples during lecture Identifying Characteristics of Epithelial Cells
Simple Squamous Epithelium
Simple Cuboidal Epithelium
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Simple Columnar Epithelium
Pseudostratified Columnar Epithelium
Stratified Squamous Epithelium
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Gland Formation
Modes of Secretion
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Epithelial Tissue Lab Materials required: Prepared slides, 1 microscope per pair, intNB, colored pencils.
Part A: Microscopic Specimens Your assignment is to carefully view the following prepared microscopic slides, locate the epithelial tissue on the slide and then carefully draw a replication of what you are seeing under the microscope. NOTE: if you do not follow proper scientific drawing guidelines, you may not receive credit.
Tips for Success: Here is an example of the quality needed to receive credit for scientific drawings.
Microscopic Original
Reproduced Hand-drawn Image
Required Slides to Study: A. Simple Columnar – Stomach OR Simple Ciliated B. Stratified Squamous C. Simple Cuboidal – kidney D. Transitional – urinary bladder E. Pseudostratified Ciliated Columnar Produce your drawings in your intNB (pgs 169 and 170). Be sure to do the following for EACH specimen: 1. Name the tissue and Indicate the magnification of the image 2. Color it correctly – as you saw it in the scope 3. Label it with leader lines – horizontal lines, neat labels. Use the following labels when it is possible for each image: a. Apical surface and basement membrane b. Nucleus c. Lumen d. Connective Tissue 4. Annotate. Explain structure (anatomy), function (physiology), location for each tissue. 5. Extra Credit: Choose the Small Intestine slide. Find the lumen, draw the epithelial tissue and identify the type of epithelial tissue found. Hint – lumen in small intestine is in the middle of it. Label and annotate as usual.
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Epithelial Tissue Lab Title:
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Epithelial Tissue Lab Part B: Tissue Review Tissue Structure and Function – General Review 1. Define a tissue: 2. Use the key choices to identify the major tissue types described below: KEY: A. connective tissue B. epithelium C. muscle D. nervous tissue a.
lines body cavities and covers the body’s external surface
b.
pumps blood, flushes urine out of the body, allows one to jump
c.
transmits electrochemical impulses
d.
anchors, packages, and supports body organs
e.
cells of this type may absorb, secrete, or filter
f.
most involved in regulating and controlling body functions
g.
major function is to contract
h.
synthesizes hormones
i.
the most durable tissue type
j.
contains an abundant amount of nonliving extracellular material
k.
most widespread tissue in the body
l.
forms nerves and the brain
3. Describe five key characteristics of epithelial tissue
4. On what basis are epithelial tissues classified?
5. How is the function of epithelium reflected in its physical arrangement?
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Label the tissue types illustrated here. Identify all structures provided with leaders. For each, also identify the lumen space. Color the illustrations in an organized manner. For example, all connective tissue can be colored the same, yellow, for instance.
a. ________________________
b. ____________________________
c. ________________________
d. ________________________
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6. Where is ciliated epithelium found?
7. What role does it play in the body?
8. Transitional epithelium is actually stratified squamous epithelium, but there is something special about it. How does it differ structurally from other stratified squamous epithelia?
9. How does the above difference reflect its function in the body?
10. Respond to the following with the choices listed below. KEY:
A. pseudostratified ciliated columnar B. simple columnar C. simple cuboidal D. simple squamous E. stratified squamous F. transitional
a.
made of one layer of cubed cells
b.
forms the epidermis of the skin
c.
lines the bladder, peculiar cells that can slide over each other
d.
made up of many layers of flattened cells
e.
composed of one layer of long thin cells
f.
found lining bronchial tubes
g.
makes up the alveolar sacs of lungs
h.
makes up the tubules in the kidneys
i.
the thinnest, most delicate epithelial tissue
j.
made up of one layer of cells, but appears to be multi layered
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Unit Packet 4a Introduction to Tissues, Epithelial Tissues, and Glands
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Identify the following epithelial tissues and label each of the structures with leaders. Color the basement membrane, and highlight the apical surface, and color one to three nuclei to show the shape of the nuclei in the tissues, particularly focusing on nuclei that change shape.
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6.
7.
8.
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Color ONE pathway of the endomembrane system to show how mucus globules are released from goblet cells, starting with the rough endoplasmic reticulum.
Endoplasmic Reticulum
1. What appears to take up the majority of the space in the globlet cell and which organelle produces this structure? _____________________________________________________ _________________________________________________________________________ 2. What is contained within this structure?_______________________________________ 3. Relate how the endomembrane system (rough Endoplasmic Reticulum and Golgi Body, specifically) are involved in the goblet cell’s primary function. ________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________
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9.
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Reading Guide: Chapter 4b Connective, Nervous, and Muscle Tissue Membranes and Tissue Repair Instructions: The specific instructions for various activities in the reading guides can be found in your reference pages you saved in your backpack on edmodo. Refer to these pages carefully, as you will be completing reading guides all throughout this year. Since reading guides are a type of formative assessment, they are graded on completion, follow-through with guidelines, and quality. 1. Read pgs. 126-130: Connective Tissue Introduction, Common Characteristics of Connective Tissue, and Structural Elements of Connective Tissue On page 185 of your intNB, write a GIST that explains how ALL connective tissues are the same STRUCTURALLY. On page 184 of your intNB, color the areolar tissue and complete the matching section. 2. Read pgs 131 – 139: Types of Connective Tissue. On page 187 of your intNB, create a flow-chart or concept map to organize the different types of connective tissue. Your concept map must connect the following terms in concept “bubbles” to show their interconnected relationship: Connective Tissue, Connective Tissue Proper, Loose Connective Tissue, Dense Connective Tissue, Areolar, Adipose, Reticular, Dense Regular, Dense Irregular, Elastic, Cartilage, Hyaline, Fibrocartilage, Bone, Blood. In addition, for each of the above terms, include TWO significant facts related to each bubble. The concept map has been started for you. 3. Read pgs 139-143: Nervous and Muscle Tissue; Covering and Lining Membranes On page 189 of your intNB, create an illustration of a neuron. Label the cell body, dendrites, and axon of the neuron. Be sure to use color. On page 189 of your intNB, illustrate the differences between a skeletal muscle, cardiac muscle, and smooth muscle in the 3-column table provided. Label your illustrations with “appropriate” structural characteristics to show the differences. Use color. On page 188, label the various types of muscle and nervous tissue. In the image, color a single cell in the tissue. 4. Read pgs 143 – 145 On page 186 of your intNB, write a GIST about Tissue Repair.
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Areolar Tissue
Coloring Instructions: collagen fibers [A] yellow. fibroblasts [B] blue. mast cells [C] purple . macrophages [D] orange elastic fibers [E] green (shade over the line) □ blood vessel and blood cells [F] red. □ fat cells [G] pink. □ □ □ □ □
Match the structure to the function (use letters) 1. ____ 2. ____ 3. ____ objects 4. ____ 5. ____
Store energy Production of fibers Consume debris and foreign Fiber that makes up tendons Prevention of blood clots
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Reading Guide Chapter 4b: Connective, Nervous, Muscle Tissue Membranes and Tissue Repair GIST 1
STRUCTURAL similarities in Connective Tissue
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GIST 2
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Connective Tissue Concept Map
Dense Connective Tissue
Connective Tissue
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188
Neuron of Nervous Tissue
Muscular System
Skeletal Muscle Cardiac Muscle Smooth Muscle 189
Label the ground substance, as in lecture:
Fill in notes on Fibers of the Extracellular Matrix next to images: Collagen:
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Ch. 4b: Connective Tissue and Tissue Repair
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Elastic Fiber:
Reticular Network:
Label the Loose Connective Tissue Areolar:
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Label the Loose Connective Tiissue: Adipose
Label the Loose Connective Tissue: Reticular Network
Label the Dense Connective Tissue:
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Label the Dense Irregular Connective Tissue:
Label the Hyaline Cartilage:
Label the Elastic Cartilage:
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Label the Fibrocartilage:
Identify which of the following is blood tissue and which is bone tissue. Label the tissue, as directed by your teacher.
a) _______________________
b) ________________________
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To the right of the images, take notes from lecture on the steps to tissue repair: Step 1:
Step 2:
Step 3:
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Connective Tissue Lab Materials required: Prepared slides, 1 microscope per pair, colored pencils (your responsibility to supply), pencil for drawing.
Part A: Microscopic Specimens Your assignment is to carefully view the following prepared microscopic slides, locate the connective tissue on the slide and then carefully draw a replication of what you are seeing under the microscope.
Tips for Success:
ALWAYS view your slides under the highest objective Each slide is worth between $5-10. DO NOT DROP these!!! Your drawings should be completely accurate – not just circles or columns. If your picture does not look like hyaline cartilage, it CANNOT receive full credit. Your drawings should be in color and the color should match that seen on the slide. You do NOT have to draw every single cell you see in your field of view. Your drawings will serve as notes for the exam on this unit. The better your drawings, the more they will help you in preparation for the portion of the exam that utilizes microscopic images!
Required Slides to Study: A. Adipose B. White Fibrous – which is Dense Regular C. Areolar
D. E. F. G.
Elastic cartilage Hyaline cartilage Bone dry ground Blood
H. Extra Credit: Examine the pseudostratified epithelium slide and locate the cartilage. Draw, label, and identify it. Annotate as usual. Produce your drawings on pages of your intNB (pgs 203-205). Be sure to do the following for EACH specimen: 1. 2. 3. 4.
Name the tissue and indicate the magnification of the image Color it correctly – as you saw it in the scope Annotate: Structural Characteristics (Anatomy), Function (Physiology), Location Label it with leader lines – horizontal lines, neat labels. Use the following labels when it is possible for each image: a. Fibers if they are present/visible. Name the specific fibers, note arrangement, of fibers and annotate why those specific fibers are needed in that arrangement. b. Nucleus if visible. Name the cell that the nucleus belongs to. For example, nucleus of chondrocyte c. Lacunae if they exist in the tissue d. Ground substance, if you can distinguish it e. Check your notes on these types of tissues. And label all identifying characteristics of each. i. For example, you should label adipocytes, fat droplet, displaced nucleus, and blood vessel for Adipose Loose Connective Tissue. In Elastic Cartilage, you should have labeled lacuna, chondrocyte, elastic fibers, ground substance, etc.
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Connective Tissue Lab Title:
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Extra Credit: Find the Pseudo-stratified Epithelium slide and locate the cartilage found among the tissue. What type of cartilage is this?
What is the purpose of that cartilage? (It is around the trachea)
Draw, label, and annotate your slide
Title:
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Connective Tissue Lab Part B: Tissue Review Connective Tissue: 1. What are three general characteristics of connective tissues?
2. What functions are performed by connective tissue?
3. How are the functions of connective tissue reflected in its structure?
Using the key, choose the best response to identify the connective tissues described below. Key: a. b. c. d. e. f. g. h. i.
Adipose connective tissue Areolar connective tissue Dense fibrous connective tissue Elastic cartilage Fibrocartilage Hematopoietic tissue Hyaline cartilage Bone Dense Irregular CT
1. 2. 3. 4. 5. 6. 7. 8. 9.
_____Attaches bones to bones and muscles to bones _____Acts as a storage depot for fat _____The dermis of the skin _____Makes up the intervertebral discs _____Forms the hip bone _____Composes basement membranes; a soft packaging tissue with a jelly like matrix _____Forms the larynx, the costal cartilages of the ribs, and the embryonic skeleton _____Provides a flexible framework for the external ear _____Firm, structurally amorphous matrix heavily invaded with fibers; appears glassy and smooth 10. _____Matrix hard owing to calcium salts; provides levers for muscles to act on 11. _____Insulates against heat loss
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What makes adipose cells look kind of like a ring with a single jewel?
Nervous tissue 1. What two physiological characteristics are highly developed in neurons (nerve cells)?
2. In what ways are neurons similar to other cells?
3. How are they different from other cells?
4. Describe how the unique structure of a neuron relates to its function in the body.
Muscle Tissue The three types of muscle tissue exhibit similarities as well as differences. Check the appropriate space in the chart to indicate which muscle types exhibit each characteristic. Characteristic Voluntarily controlled Involuntarily controlled Striated Has a single nucleus in each cell Has several nuclei per cell Allows you to direct your eyeballs Found in the walls of the stomach, uterus and arteries Contains spindle-shaped cells Contains branching cylindrical cells Contains long, no branching cylindrical cells Has intercalated discs Concerned with locomotion of the body as a whole Changes the internal volume of an organ as it contracts Tissue of the heart
Skeletal
Cardiac
Smooth
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Label the tissue types illustrated here. Identify all structures provided with leaders. You do not need to color.
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Connective Tissue Lab Part C: Table of Connective Tissue Characteristics Be sure to remark on amount of fibers, ground substance, presence of lacunae, etc. when describing distinctive characteristics. Use Notes, Textbook and Lab Manual to complete this.
Type of Tissue
Loose or Dense?
Distinctive Characteristics
Locations in the body/ Functions
Sketch of typical cells
Areolar
Adipose
Dense Regular
Dense Irregular
Hyaline Cartilage
Elastic Cartilage
Fibrocartilage
Bone
Blood
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Label the tissue types illustrated here. Identify all structures provided with leaders. You do not need to color.
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Label the tissue types illustrated here. Identify all structures provided with leaders. You do not need to color.
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Label the tissue types illustrated here. Identify all structures provided with leaders. Color the matrix only, a pale color. Leave the cells colorless.
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Tissue Engineering: How to Build a Heart With thousands of people in need of heart transplants, researchers are trying to grow new organs July 8, 2013 |By Brendan Maher and Nature magazine OTT LAB/MASSACHUSETTS GENERAL HOSPITAL From Nature magazine Doris Taylor doesn't take it as an insult when people call her Dr Frankenstein. “It was actually one of the bigger compliments I've gotten,” she says — an affirmation that her research is pushing the boundaries of the possible. Given the nature of her work as director of regenerative medicine research at the Texas Heart Institute in Houston, Taylor has to admit that the comparison is apt. She regularly harvests organs such as hearts and lungs from the newly dead, re-engineers them starting from the cells and attempts to bring them back to life in the hope that they might beat or breathe again in the living. Taylor is in the vanguard of researchers looking to engineer entire new organs, to enable transplants without the risk of rejection by the recipient's immune system. The strategy is simple enough in principle. First remove all the cells from a dead organ — it does not even have to be from a human — then take the protein scaffold left behind and repopulate it with stem cells immunologically matched to the patient in need.Voilà! The crippling shortage of transplantable organs around the world is solved. In practice, however, the process is beset with tremendous challenges. Researchers have had some success with growing and transplanting hollow, relatively simple organs such as tracheas and bladders. But growing solid organs such as kidneys or lungs means getting dozens of cell types into exactly the right positions, and simultaneously growing complete networks of blood vessels to keep them alive. The new organs must be sterile, able to grow if the patient is young, and at least nominally able to repair themselves. Most importantly, they have to work — ideally, for a lifetime. The heart is the third most needed organ after the kidney and the liver, with a waiting list of about 3,500 in the United States alone, but it poses extra challenges for transplantation and bioengineering. The heart must beat constantly to pump some 7,000 litres of blood per day without a back-up. It has chambers and valves constructed from several different types of specialized muscle cells called cardiomyocytes. And donor hearts are rare, because they are often damaged by disease or resuscitation efforts, so a steady supply of bioengineered organs would be welcome.
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Taylor, who led some of the first successful experiments to build rat hearts, is optimistic about this ultimate challenge in tissue engineering. “I think it's eminently doable,” she says, quickly adding, “I don't think it's simple.” Some colleagues are less optimistic. Paolo Macchiarini, a thoracic surgeon and scientist at the Karolinska Institute in Stockholm, who has transplanted bioengineered tracheas into several patients, says that although tissue engineering could become routine for replacing tubular structures such as windpipes, arteries and oesophagi, he is “not confident that this will happen with more complex organs”. Yet the effort may be worthwhile even if it fails, says Alejandro Soto-Gutiérrez, a researcher and surgeon at the University of Pittsburgh in Pennsylvania. “Besides the dream of making organs for transplantation, there are a lot of things we can learn from these systems,” he says — including a better basic understanding of cell organization in the heart and new ideas about how to fix one.
The Scaffold For more than a decade, biologists have been able to turn embryonic stem cells into beating heartmuscle cells in a dish. With a little electrical pacemaking from the outside, these engineered heart cells even fall into step and maintain synchronous beating for hours. But getting from twitching blobs in a Petri dish to a working heart calls for a scaffold to organize the cells in three dimensions. Researchers may ultimately be able to create such structures with threedimensional printing — as was demonstrated earlier this year with an artificial trachea. For the foreseeable future, however, the complex structure of the human heart is beyond the reach of even the most sophisticated machines. This is particularly true for the intricate networks of capillaries that must supply the heart with oxygen and nutrients and remove waste products from deep within its tissues. “Vascularity is the major challenge,” says Anthony Atala, a urologist at Wake Forest 214
University in Winston-Salem, North Carolina, who has implanted bioengineered bladders into patients and is working on building kidneys. The leading techniques for would-be heart builders generally involve reusing what biology has already created. One good place to see how this is done is Massachusetts General Hospital in Boston, where Harald Ott, a surgeon and regenerative-medicine researcher, demonstrates a method that he developed while training under Taylor in the mid-2000s. Suspended by plastic tubes in a drum-shaped chamber made of glass and plastic is a fresh human heart. Nearby is a pump that is quietly pushing detergent through a tube running into the heart's aorta. The flow forces the aortic valve closed and sends the detergent through the network of blood vessels that fed the muscle until its owner died a few days before. Over the course of about a week, explains Ott, this flow of detergent will strip away lipids, DNA, soluble proteins, sugars and almost all the other cellular material from the heart, leaving only a pale mesh of collagen, laminins and other structural proteins: the 'extracellular matrix' that once held the organ together. The scaffold heart does not have to be human. Pigs are promising: they bear all the crucial components of the extracellular matrix, but are unlikely to carry human diseases. And their hearts are rarely weakened by illness or resuscitation efforts. “Pig tissues are much safer than humans and there's an unlimited supply,” says Stephen Badylak, a regenerative-medicine researcher at the University of Pittsburgh. The tricky part, Ott says, is to make sure that the detergent dissolves just the right amount of material. Strip away too little, and the matrix might retain some of the cell-surface molecules that can lead to rejection by the recipient's immune system. Strip away too much, and it could lose vital proteins and growth factors that tell newly introduced cells where to adhere and how to behave. “If you can use a milder agent and a shorter time frame, you get more of a remodelling response,” says Thomas Gilbert, who studies decellularization at ACell, a company in Columbia, Maryland, that produces extracellular-matrix products for regenerative medicine. Through trial and error, scaling up the concentration, timing and pressure of the detergents, researchers have refined the decellularization process on hundreds of hearts and other organs. It is probably the best-developed stage of the organ-generating enterprise, but it is only the first step. Next, the scaffold needs to be repopulated with human cells.
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The Cells 'Recellularization' introduces another slew of challenges, says Jason Wertheim, a surgeon at Northwestern University's Feinberg School of Medicine in Chicago, Illinois. “One, what cells do we use? Two, how many cells do we use? And three, should they be mature cells, embryonic stem cells, iPS [induced pluripotent stem] cells? What is the optimum cell source?” Using mature cells is tricky to say the least, says Taylor. “You can't get adult cardiocytes to proliferate,” she says. “If you could, we wouldn't be having this conversation at all” — because damaged hearts could repair themselves and there would be no need for transplants. Most researchers in the field use a mixture of two or more cell types, such as endothelial precursor cells to line blood vessels and muscle progenitors to seed the walls of the chambers. Ott has been deriving these from iPS cells — adult cells reprogrammed to an embryonic-stem-cell-like state using growth factors — because these can be taken from a patient in need and used to make immunologically matched tissues. In principle, the iPS-cell approach could provide the new heart with its full suite of cell types, including vascular cells and several varieties of heart-muscle cell. But in practice, it runs into its own problems. One is the sheer size of a human heart. The numbers are seriously under-appreciated, says Ott. “It's one thing to make a million cells; another to make 100 million or 50 billion cells.” And researchers do not know whether the right cell types will grow when iPS cells are used to recapitulate embryonic development in an adult heart scaffold. As they colonize the scaffold, some of the immature cells will take root and begin to grow. But urging them to become functional, beating cardiomyocytes requires more than just oxygenated media and growth factors. “Cells sense their environment,” says Angela Panoskaltsis-Mortari, who has been trying to build lungs for transplant at the University of Minnesota in Minneapolis. “They don't just sense the factors. They sense the stiffness and the mechanical stress,” which in turn pushes the cells down their proper developmental path. So researchers must put the heart into a bioreactor that mimics the sensation of beating. Ott's bioreactors use a combination of electrical signals — akin to a pacemaker — to help to synchronize the beating cardiomyocytes seeded on the scaffold, combined with physical beating motions induced by a pump. But researchers face a constant battle in trying to ape the conditions present in the human body, such as changes in heart rate and blood pressure, or the presence of drugs. “The body reacts to things and changes the conditions so quickly it's probably impossible to mimic that in a bioreactor,” says Badylak.
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When Taylor and Ott were first developing bioreactors, for decellullarized and repopulated rat hearts, they had to learn as they went along. “There was a lot of duct tape in the lab,” Ott says. But eventually the hearts were able to beat on their own after eight to ten days in the bioreactor, producing roughly 2% of the pumping capacity of a normal adult rat heart. Taylor says that she has since got hearts from rats and larger mammals to pump with as much as 25% of normal capacity, although she has not yet published the data. She and Ott are confident that they are on the right path. The beat The final challenge is one of the hardest: placing a newly grown, engineered heart into a living animal, and keeping it beating for a long time. The integrity of the vasculature is the first barrier. Any naked bit of matrix serves as a breeding ground for clots that could be fatal to the organ or the animal. “You're going to need a pretty intact endothelium lining every vessel or you're going to have clotting or leakage,” says Gilbert. Ott has demonstrated that engineered organs can survive for a time. His group has transplanted a single bioengineered lung into a rat, showing that it could support gas exchange for the animal, but the airspace fairly quickly filled with fluids. And an engineered rat-kidney transplant that Ott's group reported early this year survived without clotting, but had only minimal ability to filter urine, probably because the process had not produced enough of the cell types needed by the kidney. Ott's team and others have implanted reconstructed hearts into rats, generally in the neck, in the abdomen or alongside the animal's own heart. But although the researchers can feed the organs with blood and get them to beat for a while, none of the hearts has been able to support the blood-pumping function. The researchers need to show that a heart has much higher ability to function before they can transplant it into an animal bigger than a rat. With the heart, says Badylak, “you have to start with something that can function pretty well” from the moment the transplant is in place. “You can't have something pumping just 1 or 2 or 5% of the ejection fraction of the normal heart and expect to make a difference,” he says, referring to a common measure of pumping efficiency. There is little room for error. “We're just taking baby steps,” says Panoskaltsis-Mortari. “We're where people were with heart transplant decades ago.” The decellularization process being cultivated by Ott and others is already informing the development of improved tissue-based valves and other parts of the heart and other organs. A bioengineered valve, for example, may last longer than mechanical or dead-tissue valves because they have the potential to grow with a patient and repair themselves. And other organs may not need to be replaced entirely.
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“I'd be surprised if within the next 5–7 years you don't see the patient implanted with at least part of an artery, lobes of a lung, lobes of a liver,” says Badylak. Taylor suspects that partial approaches could aid patients with severe heart defects such as hypoplastic left heart syndrome, in which half the heart is severely underdeveloped. Restoring the other half, “essentially forces you to build the majority of the things you need”, she says. And these efforts could hold lessons for the development of cell therapies delivered to the heart. Researchers are learning, for example, how heart cells develop and function in three dimensions. In the future, partial scaffolds, either synthetic or from cadavers, could allow new cells to populate damaged areas of hearts and repair them like patches. The jars of ghostly floating organs might seem like a gruesome echo of the Frankenstein story, but Taylor says her work is a labour of love. “There are some days that I go, 'Oh my god, what have I gotten into?' On the other hand, all it takes is a kid calling you, saying 'Can you help my mother?' and it makes it all worthwhile.”
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Tissue Engineering Project Description You are a biomedical engineer working for Tissue Biomedical Engineering. Your job is to design a tissue-like material to replace a broken long bone. Specifically, you will be designing the scaffold of one OSTEON. Follow the instructions below to complete your design. Then, conduct a load test on your substitute material. Finally, determine how many units are needed for your design to meet the requirements, and complete a cost analysis to determine which company will provide you with the lowest cost materials. Initial Design/Model: Our substitute “tissue” material will be a plain piece of paper to act as the scaffold. In the space below, sketch a model of your bone tissue with the proper dimensions. For example, is it square, rectangular, circular? Is it hollow? Solid? Justify the design shape you chose in your annotation. What is the diameter? What is the length of your bone tissue? Why did you choose a smaller or larger diameter? It is fine to use a bit of research before coming up with a design.
Annotation explaining initial design:
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Load Test Conduct a load test to determine the strength of your substitute material. Setup your experiment as shown in the diagram below.
Structure
Support
Cup
Support
Add pennies to the cup and observe the effect on the structure. Continue to add pennies until the structure fails. Record the number of pennies at failure below. Number of pennies at structure failure: _________ Average Mass of one penny: ___________ (average mass of several pennies) Failure Load of structure (number of pennies x mass of one penny): _________ grams. Show work in the space below:
Design Requirements Your design must be able to support a load of 70 kg. How many of structures do you need in your design to support this load? Show your work in the space below.
Number of structures needed: ________
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Collaborative Data Group
Size of
Diameter
Paper
(cm or mm)
(L x W in
Shape
Failure Load of
Number of
Structure
Structures Needed
cm) 1 2 3 4 5 6 7 8
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Cost Analysis You have two options in obtaining the materials you need for your design. You can either order the materials from Acme Labs, which will cost you $8 per unit that you order, or you can have your own company do the manufacturing, which will only cost you $2 per unit plus a one-time fee of $2000 to purchase the necessary manufacturing equipment. Use the instructions below to determine which is the better option. First, write equations to represent the cost associated with each supplier. Let Y be the total cost and X be the cost per unit. Acme Labs:
Your company:
Next, solve this system of equations for the number of units. This will give you the break-even point, where the two suppliers will cost you the same amount.
Solution: (
,
)
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At values below this solution or break-even point, one company’s product is cheaper than the other. Above the solution or break-even point, the other company is cheaper. Based on your design (the number of units you need) which supplier should you use if you were only going to make one of your product? Why? Make sure you justify your claim with evidence.
Your initial design is implemented and is successful, thus you get orders to make 100 more. Which company should you use now to supply the parts? Why? Make sure you justify your claim with evidence.
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Consider the original model you made of your scaffold of bone tissue, the cost analysis you just did on the previous pages, and the collaborative class data that was recorded by other engineers. How would you change and improve upon the initial design of bone tissue? ** Hint: Consider how you can redesign your bone so you need fewer structures to fulfill the design requirements of 70 kg or take a look at other models and see what worked for them. Redraw the new improved design of your bone tissue, and label the dimensions. Justify in the annotations, the reason(s) for implementing this new design.
Annotation: Justify this new improved design. Consider, what was the problem with the starting design? How is this design different and how did this new design resolve the problem?
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Building the Prototype Now that you have completed the design plan for your bone tissue, your company, Tissue Biomedical Engineering, must create a prototype of your bone scaffold. Think about the structure of a long bone and the number of units you need in order to support 70 kgs. To accomplish this task, you will do the following: With your group, construct your prototype and return to class with a prototype of the scaffold for the shaft of the long bone. You will probably have each member roll a specific number of osteons to the specifications that you designed, then make arrangements with each other to complete the prototype. You may need additional materials to “bind” your osteons together and create a medullary cavity for the marrow. What type of tissue(s) do you think are responsible for “binding” your osteons? In addition, add channels for blood vessels to exit as well as enter the medullary cavity. Accompany your prototype with a written explanation of your prototype. This description should include an explanation of the anatomy of a long bone. (Yes, you need to research this!) Then justify how your prototype fits the anatomical as well as the structural needs of a femur. In addition, discuss additional materials you used to complete the prototype and why you needed these materials.
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Discuss these terms in your lab group, and circle the term that does not belong. Your lab group must have consensus and be ready to justify/defend your choices with the class.
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Chapter 4b Unit Packet Connective, Nervous, and Muscle Tissues Membranes Tissue Repair 227
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Tissues: Unit Concept Map Organize your concept map by identifying major concepts from each of the objectives found on pages 153 and 183. Then use a different color to add associated terms to the major concepts identified.
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Summary of One Objective Choose one student objective from the start of the unit (page 153 or 183) and thoroughly explain the objective question in your writing. Use the vocabulary that was included in your concept map. Be specific with your language to communicate your understanding of the unit. Underline or highlight vocabulary words that were incorporated in your summary. Write the Objective in the Space Below:
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