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Medical Terminology Daily (MTD) is a blog sponsored by Clinical Anatomy Associates, Inc. as a service to the medical community, medical students, and the medical industry. We will post a workweek daily medical or surgical term, its meaning and usage, as well as biographical notes on anatomists, surgeons, and researchers through the ages. Be warned that some of the images used depict human anatomical specimens.

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A Moment in History

Antoine Louis
(1723–1792)

French surgeon, anatomist, and physiologist. Following his medical studies and a long career as a physiologist, Antoine Louis was named Permanent Secretary of the Royal French Academy of Surgery. His other titles were those of Professor of the Royal Academy, Consultant Surgeon of the Armies of the King, member of the Royal Society of Sciences of Montpellier, Inspector of the Royal Military Hospitals, and Doctor in Law of the University of Paris. As a member of these academies Louis was instrumental in the design and construction of the guillotine. Initially called the "Louisette", this device was later named after another French physician in the same committee, Dr. Joseph-Ignace Guillotin.

Antoine Louis' name is better know to history as the eponymic origin of the "sternal angle" also know as the "Angle of Louis" and synonymously (probably by misspelling or translation) the "angle of Lewis", and "angle of Ludwig". This anatomical landmark is extremely important as it serves as a superficial landmark for important anatomical occurrences (click here).

As a point of controversy, there are some that contest the history of this eponym adjudicating it to Pierre Charles Alexander Louis (1787-1872), another French physician dedicated to the study of tuberculosis.

Sources:
1. Srickland, N; Strickland A Angle of Louis, More Than Meets the Eye. MedTalks:
2. Ramana, R. K., Sanagala, T. and Lichtenberg, R. (2006), A New Angle on the Angle of Louis. Congestive Heart Failure, 12: 197–199
3
. "The origin of Medical Terms" Skinner, HA; 1970


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Supraspinatus muscle

The supraspinatus muscle is found in the supraspinatus fossa of the scapula, and one of the four muscles that forms the rotator cuff. The muscle attaches to the medial two thirds of the floor of the fossa directly on the bone and on the deep aspect of the supraspinatus fascia which covers the muscle. The supraspinatus fascia and the supraspinatus fossa form an osteofascial case for the origin of this muscle.

The fibers of the muscle converge and pass deep to the acromion, forming an osseous tunnel that could entrap the muscle and tendon causing a supraspinous impingement syndrome. The side image in this article has the acromion cut off to show the muscle better. The animated image at the bottom of the article shows the supraspinatus muscle and its relation to the acromion process.

The supraspinatus tendon attaches to the capsule of the glenohumeral joint at the level of the highest of the three impressions that form the greater tubercle of the humerus.

Supraspinatus muscle - Image modified from the original by Henry VanDyke Carter, MD. Public domain
Supraspinatus muscle.
Click on the image for a larger depiction 
It receives innervation by way of the suprascapular nerve (C5, C6), which arises from the superior trunk of the brachial plexus.

The main function of the supraspinatus muscle is to abduct the arm. As part of the shoulder’s rotator cuff it helps prevent subluxation of the glenohumeral joint by keeping the head of the humerus in situ.

Note: The side image modified from the original by Henry VanDyke Carter, MD. Public domain. Animated image below by Wikimedia Commons - Anatomography [CC BY-SA 2.1 jp (https://creativecommons.org/licenses/by-sa/2.1/jp/deed.en)]

Anatomography [CC BY-SA 2.1 jp (https://creativecommons.org/licenses/by-sa/2.1/jp/deed.en)]

Sources:
1. “Gray’s Anatomy” Henry Gray, 1918
2. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
3. "Gray's Anatomy" 38th British Ed. Churchill Livingstone 1995


Subscapular muscle (subscapularis)

The subscapular muscle or subscapularis is a large triangular muscle which is found on the anterior aspect of the scapula, in close relation to the posterolateral aspect of the thorax. It is covered by a well-defined fascia layer, the subscapularis fascia. It is one of the muscles that forms the rotator cuff.

It originates from the internal aspect of the medial border of the scapula, in close proximity to the insertion of the serratus anterior (magnus), and the internal aspect of the inferolateral border of the scapula, where it is separated from the teres major muscle by a thick aponeurosis. It also takes origin directly from the subscapular fossa, where some of the muscular fibers attach directly to the bone.

The muscle inserts by way of a tendon in the lesser tubercle of the humerus and the anterior aspect of the glenohumeral joint capsule. The tendon of the muscle is separated from the neck of the scapula by a large bursa (the infratendinous bursa of the subscapularis) which communicates with the cavity of the glenohumeral joint through an aperture in the capsule.

It receives innervation by two subscapular nerves, both branches of the brachial plexus.

Subscapularis muscle - Image modified from the original by Henry VanDyke Carter, MD. Public domain
Subscapularis muscle.
Click on the image for a larger depiction 
The superior suprascapular nerve arises from the ventral rami of C5 and C6 nerve fibers. It branches from the posterior cord of the brachial plexus and supplies the superior aspect of the muscle. The inferior subscapular nerve arises from the ventral rami of C5 and C6 nerve fibers. It branches from the posterior cord of the brachial plexus and supplies the superior aspect of the muscle. Although these nerves have the same origin from the cervical spine, their origin from the posterior cord of the brachial plexus is different.

This muscle rotates the head of the humerus medially. When the upper extremity is raised, it draws the humerus anteroinferiorly.  As part of the shoulder’s rotator cuff it helps prevent subluxation of the glenohumeral joint by keeping the head of the humerus in situ.

Note: The image shown in this article is from “Gray’s Anatomy” (1918) which is in the public domain

Sources:
1. “Gray’s Anatomy” Henry Gray, 1918
2. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
3. "Gray's Anatomy" 38th British Ed. Churchill Livingstone 1995
4. “An Illustrated Atlas of the Skeletal Muscles” Bowden, B. 4th Ed. Morton Publishing. 2015

Image modified from the original by Henry VanDyke Carter, MD. Public domain


Serratus anterior (magnus)

The serratus anterior or serratus magnus is a is a wide, thin muscle sheet situated on the posterolateral aspect of the thorax and extends between the ribs and the scapula. It is formed by well-defined separate muscular digitations that originate in the external surface and superior aspect of the first superior eight (or nine) ribs. These originating fibers also arise from the fasciae covering the intercostal muscles. This is especially true for the first or most superior digitation which arises from the first and second rib and the intervening external intercostal fascia.

These digitations cover the lateral aspect of the thorax, pass deep to the scapula and converge to insert on the deep aspect of the medial border of the scapula. Some of its fibers may even hug the medial border of the scapula and insert on its anterior aspect. The first digitation is inserted into a triangular area on the ventral surface of the medial scapular angle. The next two digitations spread out to form a triangular sheet, the base of which is directed posteriorly and is inserted into nearly the whole length of the ventral surface of the vertebral border. The lower five or six digitations converge to form a fan-shaped mass, the apex of which inserts into a triangular impression on the ventral surface of the inferior scapular angle. The lower four slips of the serratus anterior interdigitate with the superior five muscular slips of the external oblique muscle.

Serratus magnus muscle - Image modified from the original by Henry VanDyke Carter, MD. Public domain
Serratus magnus muscle.
Click on the image for a larger depiction 
This muscle receives its nerve supply from the long thoracic nerve, (ventral rami of C5-C7), arising from the roots of C5, C6, and C7 (sometimes absent) of the brachial plexus

The word “serratus” is derivates from the Latin word [serro] meaning “saw”. Serratus means “serrated” referring to the multiple tooth-like anterior digitations of the muscle. The plural form for "serratus" is " serrati". The Latin term “magnus” means “great”, “large”, or “mighty”. It points to the fact that this is the largest of three muscles that carry the same name “serratus”. The other two are the serratus posterior superior and the serratus posterior inferior.

Note: The image shown in this article is from “Gray’s Anatomy” by Henry Gray (1918) which is in the public domain. It depicts the serratus anterior in situ and shows the scapula retracted posteriorly.  The scapula is covered on its internal aspect by the subscapularis muscle (number 3 in the image). A better image can be found in “An Illustrated Atlas of the Skeletal Muscles” by Bowden (2015) which we cannot publish for copyright reasons.

Sources:
1. “Gray’s Anatomy” Henry Gray, 1918
2. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
3. "Gray's Anatomy" 38th British Ed. Churchill Livingstone 1995
4. “An Illustrated Atlas of the Skeletal Muscles” Bowden, B. 4th Ed. Morton Publishing. 2015

Image modified from the original by Henry VanDyke Carter, MD. Public domain


Deltoid muscle

The deltoid or deltoideus (Latin) is a large, thick, triangular muscle, which covers the glenohumeral joint anteriorly, superiorly, and posteriorly.  It can be described as having three components or segments, anterior, middle, and posterior. The anterior portion originates from the lateral third of the clavicle, on the clavicle’s superior border. The middle portion originates from the lateral border of the scapula’s acromion, and the posterior portion originates from the spine of the scapula. All three portions insert laterally by means of a thick tendon on the deltoid tuberosity of the humerus. At its insertion the muscle gives off an thick connective tissue expansion to the deep fascia of the arm.

The three portions of the deltoid muscle are usually well defined. As an anatomical variation, the clavicular or the acromial portion of the muscle may be absent.

This muscle is innervated by the axillary nerve (C5, C6), a branch of the brachial plexus, and supplied by the posterior circumflex humeral artery and the deltoid branch of the thoracoacromial artery.

The word deltoid is derivates from the Greek word [δελτοειδής] which is itself formed by the terms [δέλτα] (délta), referring to the triangular shape of the letter delta (uppercase Δ, lowercase δ or 𝛿) and [-οειδής] (-oeidís), a the Greek suffix meaning “similar to”. Delt-oid then would mean “similar to a Δ (delta)".

Deltoid muscle - Image modified from the original by Henry VanDyke Carter, MD. Public domain
Deltoid muscle.
Click on the image for a larger depiction 
Sources:
1. “Gray’s Anatomy” Henry Gray, 1918
2. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
3. "Gray's Anatomy" 38th British Ed. Churchill Livingstone 1995
4. “An Illustrated Atlas of the Skeletal Muscles” Bowden, B. 4th Ed. Morton Publishing. 2015

Image modified from the original by Henry VanDyke Carter, MD. Public domain


Pectoralis major

The pectoralis major muscle is the largest muscle in the anterior aspect of the thorax. It is thick and fan-shaped.  It attaches superiorly to the medial half of the clavicle, and medially to the anterior aspect of the sternum and cartilage of the first to sixth or seventh rib, extending inferiorly to attach to the aponeurosis of the external oblique muscle. Laterally, this muscle attaches to the lateral lip of the intertubercular groove (bicipital groove) of the humerus by a two-layered tendon which inserts each of the two heads of the muscle.

The superficial tendon attaches the clavicular head (red in the accompanying image), which extends between the intertubercular groove of the humerus and the clavicle. The deep tendon attaches the sternocostal head (purple in the accompanying image), which extends between the humeral intertubercular groove and the attachments in the sternum, costal cartilages, and the aponeurosis of the external oblique muscle. There is usually a well-defined interval between the two heads of the pectoralis major.

The pectoralis major is innervated by the medial (C8-T1) and lateral pectoral nerves (C5-C7).

This muscle is covered by the pectoral fascia which extends in different directions. An extension of this fascia is the clavipectoral fascia. In both male and female, the mammary gland is situated anterior to and anchors in the pectoral fascia.

Pectoralis major muscle - Red: clavicular head. Purple: Sternocostal head - Image modified from the original by Henry VanDyke Carter, MD. Public domain
Pectoralis major muscle - Red: clavicular head. Purple: Sternocostal head
Click on the image for a larger depiction 
The word pectoral arises from the Latin term "pectum" meaning "chest, breast". In its true meaning, pectoral or pectoralis refers to a "chest plate" or an "adornment of the chest".

Sources:
1. “Gray’s Anatomy” Henry Gray, 1918
2. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
3. "Gray's Anatomy" 38th British Ed. Churchill Livingstone 1995
4. “An Illustrated Atlas of the Skeletal Muscles” Bowden, B. 4th Ed. Morton Publishing. 2015

Image modified from the original by Henry VanDyke Carter, MD. Public domain


Dr. Elizabeth Murray Honored with American Academy of Forensic Sciences Award

We are proud to announce that our own contributor and associate Dr. Elizabeth Murray, Ph.D., has been awarded the Anthropology Section's 2018 "T. Dale Stewart Award" at the American Academy of Forensic Sciences (AAFS) 71st Annual Scientific Meeting in late February.

Dr. Murray's involvement with AAFS has included chairing the Academy-wide annual meeting as well as committee-level service in long-term planning, Board of Trustees, and the Student Academy.

Well-known and respected as a forensic anthropologist, Dr. Murray teaches at the University of Mount St. Joseph courses in anatomy and physiology, gross anatomy, and forensic science for the Department of Biology. Her most recent book, published in 2019, is "The Dozier School for Boys: Forensics, Survivors, and a Painful Past."

Our congratulations to her for yet another incredible achievement in her illustrious career. We are glad to count her as a friend and as a contributor to "Medical Terminology Daily" and Clinical Anatomy Associates, Inc.

Click here for Dr. Murray's Facebook page.