Will Stephan Pass Bio 33?

(Image courtesy of Stephan Rose,Esq.)

Instead of doing my blog today, i'd rather work out in BCC's lovely fitness center and try to get these slim arms of mine a big bigger! This has been a challenge for me, since my biceps seem the least likely of my body parts to take to weight-lifting! I think i'll do some curls...

The upper arm is made up of one bone,the humerus aka the funny bone(NEVER funny when you hit it,though). It's the larger and longest bone of the upper limb. It is attached to the scapula (shoulder) at one end, and the forearm at the other. The forearm is composed of two bones, the ulna (which is most prominent at the elbow) and the radius. At the end of the forearm that isn't attached to the upper arm(duh) is the hand. First the carpus aka wrist is composed of eight marble-sized bones. Further up the hand we have the palm,composed of the five metacarpal bones, small long bones. Our fingers are made up of the phalanges, three per fingers,except for the pointer finger, which only has two.

Synovial, the One-and-Only-al

The one joint found everywhere in the upper limb is the synovial joint. All the bones connected by synovial joints have a fluid-filled cavity between them. This joint offers the most freedom of movement. The five features of a synovial joint are *tympani drum* :

1. Hyaline cartilage (glassy-looking and smooth)covers the ends of the opposing bones. They are spongy and absorb compression. BOING!
2. A joint cavity filled with synovial fluid(how easy to remember!)
3. The cavity is surrounded by a two-layer capsule. The outer layer is tough,composed of dense connective tissue(strengthens), and the inner layer is made of loose connective tissue. It is called the synovial membrane, and it covers all internal joint surfaces that don't have hyaline cartilege on them.
4. The aforementioned synovial fluid fills all the space in the capsule. This thick and sticky liquid gets thicker as it warms up, as when the joint is being used. It reduces friction between the cartileges and has phagocytic cells that keep the cavity free of microbes and cell debris.
5. Ligaments strengthen and reinforce the synovial joints.

Usually where you find synovial joints, you find bursae. They are 'bags of lubricant' that reduce friction. They are flat sacs lined with a synovial membrane and synovial fluid inside of that. Tendon sheaths is a kind of longer bursa that wraps completely around a tendon, protecting it from friction.

The five TYPES of synovial joints are : plane, pivot,condyloid,saddle and ball-in-socket. All are found in the upper limb.

MUSKLES!

There are five main muscles in the upper limb: the triceps brachii, the anconeus, the biceps brachii, the brachialis, and the brachioradialis. The first two are found on the back of the arms, the next three on the front. (Brachi is Latin for "arm".)

The triceps have three heads, originate on the scapula and backside of the humerus, and insert by a tendon on the ulna. They extend the forearm, extend against resistance,and works opposite the forarm flexors.

The anconeus is the elbow muscle, short and triangular, originates on the humerus and ends on the ulna. It works with the triceps when extending the elbow muscle, and moves the ulna away from the body when the forearm is pronated (palm facing down).

(Image taken from http://www.fun-and-fitness.com/mus-zone.)

The biceps is a two-headed muscle that originates on the scapula and inserts on the radius. They flex the elbow and turn the palm facing back (supinated forearm),flexes the arm at the shoulder somewhat.

The brachialis is a strong muscle originating on the front of the humerus and inserting on the ulna and flexes the forearm. When the biceps lift the radius, it lifts the ulna!

(Image taken from http://www.fun-and-fitness.com/mus-zone.)

The brachioradialis is the topmost muscle on the outside of the forearm, originating on the humerus and inserting on the radius. It helps flex the forearm, and during radid flexing and extending, it stabilizes the elbow.

The forearm muscles are called flexors, and they move the fingers and the wrist.

Three Cords to Hold You, Five Nerves to Love You

(Image courtesy of http://depts.washington.edu/anesth/regional/brachialplexusanatomy.html.)

The brachial plexus is half in the neck,half in the armpit aka axilla and eventually becomes three cords or large fiber bundles: the lateral, the medial and the posterior cords. They then divide into five main nerves: axillary, musculocutaneous,median,ulnar and radial. The axillary innervates the deltoid and teres minor muscles, the musculocutaneous supplys motor fibers to the biceps and brachialis, the median activates the wrists,fingers and turns the palm down, the ulnar innervates most of the hand muscles and the forearm, and the radial innervates all the extensor muscles.

Put It All Together,It Spells...

# posted by Stephan @ 8:49 PM