Bones of the Upper Limb - Online Tutor, Practice Problems & Exam Prep

The upper limb consists of three main bones: the humerus in the upper arm, and the radius and ulna in the forearm. The humerus features a rounded head for the shoulder joint, while the radius, located on the thumb side, allows for hand rotation. The ulna, medial to the radius, forms a hinge joint at the elbow. The wrist and hand comprise three sets of bones: eight carpals, five metacarpals, and fourteen phalanges, with the thumb having two phalanges. Understanding these structures is essential for grasping human anatomy and movement.

Overview of the Arm and Forearm

Now we're going to learn how to identify the three bones that make up the arm and the forearm. We're just going to jump right in. So we're going to start with the arm, or as we often think of the upper arm. There we have one bone, and it is the humerus. The humerus, we are just going to say, is the large bone of the upper limb. And as we look over at our image here, what we start off with the pectoral girdle up here, but in green, we have the humerus there. That's that large bone of the upper limb. And then as we go down, you'll also see we'll have the radius and ulna, which we're going to go over in a second along with the wrist and hand bones there, just for reference. But as we look at the humerus there, and I can show you the actual bone here, well, to me, this is really sort of, like, very classically bone shaped. Kind of in my mind's eye, when I think of a bone, I think of the humerus or something like it. But one of the first things that I notice about it is this real round part on the top. That's called the head, and we're just going to say that it is the round part that fits into the shoulder, and we can see it on our image here labeled 1a. Remember, it fits into the glenoid cavity of the scapula and makes up that ball and socket joint of the shoulder. The other thing I noticed, well, it's got the shaft on it, but then as you go down to the bottom, it gets wider, and you can feel the ends of your humerus down there, on the elbow on the inside and outside. You're touching these parts right here, and that's what sometimes really hurts like heck when you whack your elbow on something. And then finally, there's this real curve part right here that's going to articulate with the bones of the forearm, and we'll check that out in just a second.

Okay. So as we look at the forearm, we have two bones, and they're roughly equal in size, as you can see over here in our image. We have the radius and the ulna. Well, the radius here is in orange or this orange-red color, and remember, we're looking at this in anatomical position. So we're looking hands, palms forward, thumbs out. So when we look at it like this, this is the right side of the body. The radius is going to be lateral to the ulna. Now, the way I remember that, I'm a little old, so sometimes when something's kind of cool, I say, hey, that's rad. And if you say the radius is rad, you give it a thumbs up. Well, the radius is on the thumb side of the arm. So if I take my radius here, you can see that one end's kind of round and one end's a little wider. I lined it up there, so this wider end comes down and is on the side that's given the thumbs up. This wider end, that's your wrist bone that you can feel right there. I'm going to say right here, this is the same side as the thumb. And you can see that in our image here, this wide part, and here's the thumb. Now, the other really obvious thing about the radius, and this is what helps me remember the name, is that on the head here, it has this almost perfectly round circle. Well, the name radius, there's a radius as part of a circle. It's the line that goes to the middle of the circle. Well, there's a radius in a circle. There's a circle on the radius. So I say right here, circles have a radius, and that's how I remember it. This allows you to turn your hand, and I'll show you that right now. So as we look at how this fits into the elbow joint, it's going to be on the lateral side, and it sits on this smooth part right there. And when that circle allows this bone to sort of twist in the elbow joint, and as it does that, you can look down at this thumb side, kind of moves in this big circular motion. What's happening there, that's the same thing as when I turn my hand or turn my thumb around your hand like that, what you're doing is you're having the radius spin on that round part that's in the elbow joint.

Okay. That brings us to the ulna. Now the ulna, well, if the radius is lateral, then the ulna is going to be medial to the radius. And we can see that in our image here. Right? It's sort of towards the midline of the body, because that's the right side of the body. It's on the inside. And one way to remember that, I don't have it written down here, but you can see here as we look at an ulna, the end of the ulna that comes down to your wrist here, well, it's kind of pointy, and the pointy part of the ulna is on the pinky side. So lots of p there. The pointy ulna on the pinky side. Right? That's the medial side. The way I remember the bone, though, is when you look at the elbow joint where this makes, joins the elbow, you can see there's a U in the ulna. It makes a U at the ulna. And that's where it clamps onto the humerus, and it makes a hinge with the humerus. So if I take the humerus here, this ulna just fits on really clearly and really tightly and makes this really clear hinge joint as you bend your arm back and forth. Now I can put the whole joint together. I can take my radius. I take the round part, and it fits in. There's a little notch on the ulna where it fits, and it fits down there around the other end. And so both of them can do this if you're doing curls. And then if I'm going to turn my hand, this radius will spin, and it will actually spin around the ulna. Okay. So those are the three bones that make up the arm and the forearm. We're going to talk more about how we orient them and figure out which side of the body they're on next. See you there.

Of the two bones in the forearm, which bone is medial?

• A. Humerus.
• B. Radius.
• C. Ulna.
• D. Clavicle.

When a person falls, a common reaction is to try to catch themselves by sticking out their hands. This will sometimes lead to a fracture in one or both of the bones of the forearm. Because one forearm bone is larger where it articulates with the wrist, this bone tends to absorb more force from the impact and is broken more often, making it the most commonly broken bone in the body. Where would such a break likely occur?

• A. The distal end of the ulna.
• B. The proximal end of the ulna.
• C. The distal end of the radius.
• D. The proximal end of the radius.

Bones of the Upper Limb Example 1

Our example tells us that Shravya is recently engaged and showing off her ring. Then we want to draw an X on the diagram below where the ring would be placed, and we want to know the name of the bone that the ring surrounds. Alright. We're looking at the bones of the hand here. We're looking at the left hand because that's traditionally where an engagement ring goes. And again, in anatomical position, remember it's palms forward. So that's what we're looking at. I'm going to go through here and name all the bones I see until I get to where the ring is placed. Well, first off, we have the radius and the ulna. We don't put an engagement ring there. We have the wrist bones, the carpals; that's not where an engagement ring goes. Now we're at the bones of the hand. So these are the metacarpals, and remember we number them 1 through 5 starting at the thumb. So we have the 1st, 2nd, 3rd, 4th, and 5th metacarpal. We don't put a ring on them. You put a ring on your phalanges, and an engagement ring traditionally goes on your 4th phalanx. So we're going to count over. 1, 2, 3, 4. That's your ring finger, and the proximal phalanx, that first finger bone, is what a ring traditionally surrounds. So the answer to this question, I'm going to put down as the 4th proximal phalanx. Remember, "phalanx" is singular for "phalanges". Alright. That's our answer, and congratulations to Shravya and her fiance.

Arrange the bones of the upper limb from proximal to distal. Some bones may not be included.

• A. Humerus → Radius & Ulna → Metacarpals → Phalanges
• B. Humerus → Ulna → Phalanges → Metacarpals → Carpals
• C. Humerus → Radius → Ulna → Phalanges
• D. Scapula → Ulna & Radius → Humerus → Phalanges

Often people will 'crack' their knuckle by pulling on their pointer finger. The cracking sound comes from knuckle where the finger meets the hand. What's another way to describe this location?

• A. Between the first proximal phalanx and the first metacarpal.
• B. Between the first and second phalanges of the proximal digit.
• C. Between the second proximal phalanx and the second metacarpal.
• D. Between proximal and middle phalanges of the second digit.

Here’s what students ask on this topic:

What are the main bones of the upper limb?

The upper limb consists of three main bones: the humerus, the radius, and the ulna. The humerus is the single bone in the upper arm, featuring a rounded head that fits into the shoulder joint. The forearm contains two bones: the radius and the ulna. The radius is located on the thumb side and allows for the rotation of the hand, while the ulna is medial to the radius and forms a hinge joint at the elbow. Together, these bones facilitate a wide range of movements and functions in the upper limb.

How can you differentiate between the radius and the ulna?

The radius and ulna can be differentiated based on their location and features. The radius is located on the thumb side of the forearm and has a round head that allows for hand rotation. It is lateral to the ulna. The ulna, on the other hand, is medial to the radius and features a U-shaped notch at its proximal end, which forms a hinge joint with the humerus at the elbow. Additionally, the ulna has a pointy end at the wrist, which is on the pinky side of the hand.

What are the bones of the wrist and hand?

The wrist and hand are composed of three sets of bones: the carpals, metacarpals, and phalanges. The carpals are eight short bones that make up the wrist. The metacarpals are five long bones that form the palm and back of the hand, numbered 1 to 5 starting from the thumb. The phalanges are the finger bones, with each finger having three phalanges (proximal, middle, and distal) except for the thumb, which has only two (proximal and distal).

What is the function of the humerus in the upper limb?

The humerus is the single bone in the upper arm and plays a crucial role in the upper limb's function. Its rounded head fits into the glenoid cavity of the scapula, forming the ball-and-socket joint of the shoulder, which allows for a wide range of arm movements. The distal end of the humerus articulates with the radius and ulna at the elbow, enabling flexion and extension of the forearm. The humerus also serves as an attachment point for various muscles, contributing to the strength and mobility of the arm.

How are the metacarpals and phalanges numbered in the hand?

The metacarpals and phalanges in the hand are numbered based on their position relative to the fingers. The metacarpals are numbered 1 to 5, starting from the thumb (1) to the pinky finger (5). Each finger has three phalanges: proximal, middle, and distal, except for the thumb, which has only two phalanges (proximal and distal). This numbering system helps in identifying and describing the specific bones in the hand.