BNG338 Exam 1 S17 Solution - Union Collegeorzo.union.edu/~curreyj/BME-338_files/BNG338 Exam 1... ·...

BNG -338 MechanobiologyExam 1

April 28, 2017

Name: SOLUTION

This exam is closed book, closed notes. There are 6 section/questions, please write your name on each page.

Grade:

#1 _______/ 10

#2 _______/ 10

#3 _______/ 20

#4 _______/ 20

#5 _______/ 10

#6 _______/ 30

Final Grade __________/ 100

BNG-338 Mechanobiology Exam 1

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Name:___________________________________

1. Complete the crossword puzzle using the clues. Each answer is worth 1 pt. Total 10 pts


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Name:___________________________________

2. What type of tissue is this an image of? What are the types of cells present in this tissue? Identify and describe the processes that are happening in Region A and Region B. 10 pt

Tissue is Cartilage (1 point) and the cells are chondrocytes (1 point)

Region A shows indicate apposition growth. Apposition growth is the formation of cartilage on the surface of existing cartilage. Cells initially have the appearance of fibroblasts and produce type I collagen. When cartilage growth is initiated, the cells undergo a change and become chondroblasts and secrete type II collagen. 4 points

Region B shows interstitial growth. Interstitial growth is the formation of cartilage within the cartilage mass. This is done through the process of chondrocyte division within the lacunae. The cells initially reside in the same lacunae, but as they secret matrix, they move apart and reside in different lacunae. 4 points


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Region A

Region B

Name:___________________________________

3. Analyze the following images.

(a) What are the types of tissues indicated by the histological slides A and B? Where can they can they be found and why are they found there? 4 pts

A is Hyaline Cartilage. Hyaline cartilage is 60-70% water which is bound to proteoglycans which are hydrophylic. This gives hyaline cartilage rigidity allowing it to absorb high loads. With this in mind, it is on the bone surface of joints as well as the ribs. 2 points

B is Elastic Cartilage. Elastic cartilage is similar in composition to hyaline cartilage, but it also contain elastic fibers and interconnecting sheets of elastic material. The elastin allows it to expand and contract and be flexible. With this in mind, it is found in the walls of the external auditory canal, external ear, eustachian tubes, epiglottis, and larynx. 2 points

(b) Identify and describe the common feature among these animals. 4 pts

These animals all have tetrapod limbs. The tetrapod limb consists of a single long bone (humerus or femur), followed by two smaller bones (radius/ulna or tibia/fibula) followed by an array of smaller bones of the hand or foot.


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BA

Name:___________________________________

(e) Name and describe the characteristics and functions of the cells in A, B, and C. 12 pts

A: OsteoclastB: OsteoblastC: Osteocyte3 points

Osteoclasts are giant multinucleated cells that for from hematopoietic stem cells. They are ~100 um in diameter and have a ruffled edge. They attach to the surface of bone, forming a tight seal. They secrete acid that dissolves bone and expels the debris into the blood steam. 3 points

Osteoblasts differentiate from mesenchymal stem cells. They are cuboidal in shape and secrete osteoid. They have an extensive endoplasmic reticulum. 3 points

Osteocytes reside in lacunae and are surrounded by extracellular fluid. They have cellular processes that they extend into the canaliculi and meet processes from other osteocytes. They can pass ions from one cell to the other. They are believed to be sensors of mechanical load in bone. They are derived from osteoblasts that get embedded within the matrix. 3 points


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A

B

B

C

C

Name:___________________________________

4. (a) Label the regions at A, B, and C. 5 pts

(b) Identify and describe the regions and processes depicted in this image. 15 pts

A: Zone of calcified cartilage: enlarge cells begin to degenerate and matrix becomes calcified 4 points

B: Zone of hypertrophy: cells are greatly enlarged, matrix is compressed into linear bands b/t columns of hypertrophied cells 4 points

C: Zone of proliferation: cartilage cells under go division and are organized into distinct columns, cells are larger than cells in reserve zone and are actively producing matrix 4 points

D: Zone of reserved (resting) cartilage: exhibits no cellular proliferation or matrix production 3 points


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A:B:

C:

A

B

C

D

Name:___________________________________

5. Arrange the following events in the development of bone in the order of their occurrence (Put #1 against the event which happened first, #2 against the event which happened second and likewise until #5). 10 pts


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EventOrder of

Occurrence

Muscles are well developed and contractions are apparent 3

Mesenchymal condensations of skeletal rudiments appear 1

Chondrification of femur begins 2

Vascularization of femoral chondroepiphyses begins 5

Endochondral ossification is extensive 4

6. Describe the processes happening at A and B. You can use a combination of words and pictures. 30 pts

A: This is Intramembranous ossification. It begins with mesenchymal cells migrating and aggregating in the

mesenchyme. The area becomes more vascularized and the cells become larger and rounder and differentiate into osteoblasts. The osteoblasts start

to secret osteoid, collagen, and proteoglycans. The matrix eventually become mineralized. 10 points

B: This is endochondral ossification. This process involves several steps as outlined below.

First. mesenchymal cells proliferate and differentiate into chondroblasts. Chondroblasts secrete matrix and for a bone shape comprised of

hyaline cartilage. This bone shape grows by interstitial and appositional growth

• Second, the perichondral cells stop differentiating into chondroblast and instead become osteoblasts, no longer perichondirum, now periosteum

• The periosteal bone collar causes compression of chondrocytes become hypertropic and begin to synthesize alkaline phosphatase and cartilage starts to calcify

• The calcificatoin inhibits diffusion and cells die in the cartilage matrix, bone vessels grow in from bone collar

• The periosteal cells migrate with blood vessels and become osteoprogenitor cells• when these cells come in contact with the broken down and partially removed matrix,

they become osteoblasts and begin to lay down osteoid • With all this, you get the formation of a growth plate that helps with the longitudinal

growth of the bone. 20 points


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A

B

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