Articulation Lab

We will explore the different classes of joints and their associated movements, as well as perform a dissection of fetal pig limbs and shoulders to expose the synovial joints.

There are two main structural classes of joints: fibrous joints and cartilaginous joints. Fibrous joints have little to no movement and are held together by fibrous connective tissue. Cartilaginous joints have limited movement and are held together by cartilage. The third class of joints is synovial joints, which have a wide range of motion and are the most common in the body. Synovial joints are classified by their shape and the type of movement they allow.

The six types of synovial joints are:

·         Hinge joint - allows for movement in only one plane (e.g., elbow joint)

·         Pivot joint - allows for rotation around an axis (e.g., the joint between the first and second vertebrae)

·         Ball and socket joint - allows for movement in all planes (e.g., hip joint)

·         Saddle joint - allows for movement in two planes (e.g., joint between the thumb and wrist)

·         Condyloid joint - allows for movement in two planes, but not rotation (e.g., wrist joint)

·         Gliding joint - allows for sliding movements (e.g., joints between the vertebrae)

All synovial joints have several structures in common, including the joint capsule, which is a fibrous sac that surrounds the joint, and the synovial membrane, which lines the capsule and produces synovial fluid, a lubricant for the joint. The articular cartilage covers the ends of the bones, reducing friction and allowing smooth movement. Other structures include ligaments, which connect bones to other bones, and tendons, which connect muscles to bones.

There are several types of joint movements, including:

·         Flexion - bending movement that decreases the angle between bones (e.g., bending the elbow)

·         Extension - straightening movement that increases the angle between bones (e.g., straightening the elbow)

·         Abduction - movement away from the midline of the body (e.g., lifting the arm out to the side)

·         Adduction - movement towards the midline of the body (e.g., lowering the arm to the side)

·         Rotation - movement around a longitudinal axis (e.g., rotating the head from side to side)

·         Circumduction - circular movement of a limb that includes flexion, extension, abduction, and adduction (e.g., swinging the arm in a circle)

We will also perform a dissection of fetal pig limbs and shoulders to expose the synovial joints. Through this dissection, we will observe the different types of synovial joints and their associated structures. We will also identify the movements that occur at each joint.

Articulation Dissection

In this dissection, we will focus on identifying the ball-and-socket, hinge, and carpals joints in the fore limb of the fetal pig. The ball-and-socket joint allows for a wide range of motion, while the hinge joint only allows movement in one direction. The carpals are a group of bones that make up the wrist joint.

To begin the dissection, you will need to first locate the fore limb of the fetal pig. Once you have located it, you will carefully remove the skin and muscle tissue surrounding the joints. We will then work together to identify the different types of joints in the fore limb.

After we have identified the synovial joints, we will move on to the scalp of the pig. The scalp contains sutural joints, which are joints that occur between the bones of the skull. We will carefully remove the scalp to identify these joints.

Throughout the lab, we will be emphasizing proper dissection techniques, including the use of appropriate tools and the handling of specimens with care.

By the end of this lab, you should have a thorough understanding of the different types of synovial and sutural joints in the fetal pig, as well as the skills necessary to conduct a dissection in a safe and effective manner.

Objectives

·         Identify and distinguish between ball-and-socket, hinge, and carpals joints in the fore limb of the fetal pig.

·         Demonstrate proper dissection techniques by carefully removing the skin and muscle tissue surrounding the joints of the fore limb.

·         Apply dissection skills to remove the scalp of the fetal pig and identify sutural joints occurring between the bones of the skull.

·         Employ appropriate tools and handle specimens with care throughout the dissection process.

·         Develop a comprehensive understanding of the structure and function of synovial and sutural joints in the fetal pig.

·         Gain proficiency in conducting dissections in a safe and effective manner.

·         Demonstrate knowledge of anatomical terminology associated with joints and their respective movements.

·         Analyze and interpret the relationship between joint structure and range of motion.

·         Draw connections between the fetal pig's joints and the corresponding human joints, enhancing understanding of human anatomy.

Materials

·         Fetal Pig

·         PPE

·         Dissection Kit

·         Dissection Tray

Dissection Procedure

1.   Obtain a packaged fetal pig.

2.   Write the names of the people in your group.

3.   Cut across the top of the bag to open the outer bag and then repeat with the inner bag.

a.       Keeping the inner bag inside of the outer.

b.       Keep the preserving chemicals in the inner bag.

4.   Put the pig on the dissection tray.

Limb Dissection

5.   Make a circular cut around the shoulder blade and limb. 

a.       Make sure to cut through the skin and muscles.

6.   Cut the skin around hoof

7.   Strip the skin off of the limb by pulling the skin off the muscle, starting at the shoulder pulling it towards the hoof.

a.       You may cut the skin if it gets stuck.

8.   Cut and remove the muscle from around the shoulder blade and limb

9.   Strip the tissues from bones until you expose the carpal joints, the elbow, and the shoulder 

10.   Take an image of the carpals.

11.   Take an image of the elbow.

12.   Take an image of the shoulder.

Scalp Dissection

13.   Make a cut across the nose of the pig, between the eyes.

14.   Connect the ends of the nose cut with a circular cut that cuts above the eyes, under the ears, and behind the head.

15.   Peel away the skin of the scalp.

a.       You will need to cut the ear canal between the skull and the ear.

16.   Take an image of the sutures.

Clean Up

17.   Put the pig back in the inner bag, close the inner bag by twisting the bag closed then folding the twisted bag on itself, then hold the bag closed by a rubber band

18.   Close the outer bag the same way.

19.   Remove debris from the work surface and tray and dispose of any dissection pieces in a bio-hazard bin.

20.   Place paper towels on the worksurface and put a cleaning agent (ethanol or bleach solution) on the paper towels and clean the worksurface and anything that was contaminated.

21.   Clean your dissection tools and replace everything where it belongs.

Draw a diagram of the carpal joints

Draw a diagram of the elbow joint

Draw a diagram of the shoulder joints

Draw a diagram of the sutural joints

Compare the joints of the pig and a human.  How does each location differ?  What areas are the same?

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Review Questions

1.       What is the definition of joint articulation?
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2.       Can you explain the difference between a synovial joint and a fibrous joint?
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3.       How does the structure of a hinge joint allow for movement?
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4.       How do ball-and-socket joints differ from pivot joints in terms of their movement and structure?
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5.       How might the structure and movement of a saddle joint differ from a ball-and-socket joint?
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6.       Why might the structure and movement of a gliding joint be more advantageous than a hinge joint in certain situations?
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7.       What are the three types of muscle tissue and where are they found in relation to joint articulations?
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8.       How does the action of the quadriceps muscle group affect the knee joint during movement?
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9.       How might the joint articulations of a professional tennis player differ from those of a professional swimmer, and why?
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10.    How might an understanding of joint articulations and muscle function be useful for a physical therapist treating a patient with a knee injury?
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