Definition

The shoulder joint, also called the glenohumeral joint, is a synovial, ball-and-socket
type of joint that connects the upper limb to the axial skeleton. It is the most mobile
joint in the human body.

Articulating Surfaces
The joint is formed by two main articular surfaces:

●​ The head of the humerus, which is large, spherical, and faces medially,
superiorly, and posteriorly.​

●​ The glenoid cavity of the scapula, which is shallow, pear-shaped, and directed
laterally.

The articular surfaces are covered with hyaline cartilage and are separated by the
joint cavity filled with synovial fluid.

The glenoid cavity is deepened by a fibrocartilaginous rim called the glenoid labrum,
which increases stability.

Type of Joint
The shoulder joint is a multiaxial synovial joint of the ball-and-socket variety,
allowing movement in multiple planes.

Ligaments of the Shoulder Joint

The shoulder joint is stabilized by both intrinsic and extrinsic ligaments:

1.​ Capsular Ligament​

The fibrous capsule encloses the joint and attaches medially to the glenoid
cavity and laterally to the anatomical neck of the humerus.
2.​ Glenohumeral Ligaments​
These are three thickened bands of the anterior capsule: superior, middle, and
inferior glenohumeral ligaments. They reinforce the anterior aspect of the joint.​
 3.​ Coracohumeral Ligament​
Extends from the base of the coracoid process to the greater tubercle of the
humerus and helps strengthen the upper part of the capsule.​

4.​ Transverse Humeral Ligament​

Spans between the greater and lesser tubercles of the humerus, holding the
tendon of the long head of the biceps brachii in the bicipital groove.​

5.​ Coracoacromial Ligament​

Extends from the coracoid process to the acromion, forming the coracoacromial
arch that protects the joint superiorly.​

Muscles Acting on the Shoulder Joint

Several muscles act on or support the shoulder joint:

1.​ Rotator Cuff Muscles (stabilizers)​

○​ Supraspinatus: initiates abduction​

○​ Infraspinatus: external rotation​

○​ Teres minor: external rotation​

○​ Subscapularis: internal rotation​

2.​ Deltoid: prime abductor after 15°​

3.​ Pectoralis major: adduction and internal rotation​

4.​ Latissimus dorsi: extension, adduction, internal rotation​

5.​ Teres major: internal rotation and adduction​

6.​ Biceps brachii (long head): helps with flexion and stabilizes the head of
humerus​

7.​ Triceps brachii (long head): assists in extension​

Relations of the Shoulder Joint
●​ Anterior: Subscapularis, coracobrachialis, and brachial plexus​

●​ Posterior: Infraspinatus, teres minor​

●​ Superior: Coracoacromial arch and deltoid​

Bursae Associated with the Joint

1.​ Subacromial bursa: Located between the deltoid muscle and the supraspinatus
tendon; allows smooth movement of the deltoid over the joint.​

2.​ Subscapular bursa: Lies between the subscapularis tendon and the neck of the
scapula; communicates with the joint cavity.

Movements at the Shoulder Joint

The shoulder joint allows a wide range of movements due to its ball-and-socket
structure. All movements occur around three principal axes.

1.​ Flexion and Extension:​

○​ Flexion (anterior movement) by deltoid (anterior fibers), pectoralis major,

biceps brachii.​

○​ Extension (posterior movement) by latissimus dorsi, deltoid (posterior

fibers), teres major.​

2.​ Abduction and Adduction:​

○​ Abduction by supraspinatus (initial 15°) and deltoid.​

○​ Adduction by pectoralis major, latissimus dorsi, teres major.​

3.​ Medial (Internal) and Lateral (External) Rotation:​

○​ Medial rotation by subscapularis, latissimus dorsi, teres major.​

 ○​ Lateral rotation by infraspinatus and teres minor.​

4.​ Circumduction:​

○​ A combination of all the above movements in a circular motion.​

Blood Supply
The joint is supplied by an arterial anastomosis formed by branches of:

●​ Anterior and posterior circumflex humeral arteries​

●​ Suprascapular artery​

●​ Subscapular artery​

Nerve Supply
The shoulder joint receives innervation from:

●​ Suprascapular nerve​

●​ Axillary nerve​

●​ Lateral pectoral nerve​

(Mnemonic: S.A.L)​

These nerves also contribute to proprioception and pain sensation.

Stability of the Joint
The shoulder joint sacrifices stability for mobility. Its stability is maintained by:

●​ The rotator cuff muscles​

●​ The glenoid labrum​

●​ The joint capsule and ligaments​

●​ Negative intra-articular pressure​

However, the shallow nature of the glenoid cavity makes it prone to dislocation.

Applied Anatomy
1.​ Dislocation of Shoulder​
The most common dislocation is anterior dislocation due to trauma when the
arm is abducted and externally rotated.​

2.​ Rotator Cuff Injuries​

Common in athletes and the elderly. The supraspinatus tendon is most
frequently torn.​

3.​ Frozen Shoulder (Adhesive Capsulitis)​

A condition marked by stiffness, pain, and limited movement due to inflammation
and fibrosis of the joint capsule.​

4.​ Subacromial Bursitis​

Inflammation of the subacromial bursa can cause shoulder pain, especially
during abduction.​
Definition
The brachial plexus is a network of nerve fibers that arises from the ventral
rami of spinal nerves C5 to T1, and is responsible for the motor and sensory
innervation of the upper limb.

Formation
The brachial plexus is formed in the posterior triangle of the neck, and passes
into the axilla. It is organized into five major parts in the following order:

●​ Roots​

●​ Trunks​

●​ Divisions​

●​ Cords​

●​ Branches​

A common mnemonic to remember this sequence is:​

"Randy Travis Drinks Cold Beer"

1. Roots
●​ Formed by the ventral rami of C5, C6, C7, C8, and T1​

●​ Located between the anterior and middle scalene muscles​

●​ The roots unite to form trunks.​

Branches from roots:

 ●​ Dorsal scapular nerve (C5): supplies rhomboids and levator scapulae​

●​ Long thoracic nerve (C5–C7): supplies serratus anterior​

2. Trunks
●​ Upper trunk: formed by union of C5 and C6​

●​ Middle trunk: continuation of C7​

●​ Lower trunk: formed by union of C8 and T1​

Branches from trunks:

●​ Suprascapular nerve (from upper trunk): supplies supraspinatus and

infraspinatus​

●​ Nerve to subclavius (from upper trunk): supplies subclavius muscle​

3. Divisions
Each trunk splits into two divisions:

●​ Anterior divisions: supply flexor (anterior) muscles of the limb​

●​ Posterior divisions: supply extensor (posterior) muscles of the limb​

No branches arise directly from the divisions.

4. Cords
Divisions rearrange to form three cords, named according to their position
relative to the axillary artery:

●​ Lateral cord: from anterior divisions of upper and middle trunks​

●​ Posterior cord: from all three posterior divisions​

●​ Medial cord: from anterior division of lower trunk​

5. Branches of Brachial Plexus

From Lateral Cord
1.​ Lateral pectoral nerve: supplies pectoralis major​

2.​ Musculocutaneous nerve: supplies anterior arm muscles (biceps,

brachialis)​

3.​ Lateral root of median nerve: contributes to median nerve​

From Medial Cord

1.​ Medial pectoral nerve: supplies pectoralis major and minor​

2.​ Medial cutaneous nerve of arm​

3.​ Medial cutaneous nerve of forearm​

4.​ Ulnar nerve: supplies most hand muscles and some forearm muscles​

5.​ Medial root of median nerve: joins lateral root to form median nerve​

From Posterior Cord

 1.​ Upper subscapular nerve: supplies subscapularis​

2.​ Thoracodorsal nerve: supplies latissimus dorsi​

3.​ Lower subscapular nerve: supplies subscapularis and teres major​

4.​ Axillary nerve: supplies deltoid and teres minor​

5.​ Radial nerve: supplies all extensor muscles in arm and forearm​

Functional Distribution
●​ Motor supply: All major muscles of the upper limb​

●​ Sensory supply: Skin of shoulder, arm, forearm, and hand​

●​ Sympathetic fibers: Also carried to regulate vasomotor tone and sweat

glands​

Clinical Anatomy (Applied Aspect)

1. Erb’s Palsy (Erb-Duchenne paralysis)
●​ Injury to upper trunk (C5–C6)
●​ Causes: birth trauma, fall on shoulder
●​ Presentation: arm hangs by side, medially rotated, forearm extended and
pronated ("waiter’s tip deformity")
●​ Muscles affected: deltoid, biceps, brachialis, supraspinatus, infraspinatus​
2. Klumpke’s Palsy
●​ Injury to lower trunk (C8–T1)​

●​ Causes: excessive arm abduction, birth injury​

●​ Affects intrinsic hand muscles and flexors of wrist and fingers​

●​ Presentation: "claw hand" deformity, may involve Horner's syndrome if

sympathetic fibers are damaged​

3. Long Thoracic Nerve Injury

●​ Paralysis of serratus anterior​

●​ Leads to winging of scapula, where medial border protrudes outward

when pushing against a wall​

4. Axillary Nerve Injury

●​ Often injured in shoulder dislocations or fractures of surgical neck of
humerus​

●​ Results in deltoid paralysis and loss of sensation over deltoid area​

5. Radial Nerve Injury

●​ Commonly injured in mid-shaft fracture of humerus​

●​ Leads to wrist drop, due to paralysis of wrist extensors​

Definition
The mammary gland is a modified sweat gland of ectodermal origin that functions
primarily to produce and secrete milk for the nourishment of the infant. It is present in
both sexes but is functionally active only in females.

Location
The mammary gland is located in the superficial fascia of the anterior chest wall. It
extends:

●​ Vertically: from the 2nd to the 6th rib​

●​ Horizontally: from the lateral border of the sternum to the mid-axillary line​

A small part extends toward the axilla, called the axillary tail (of Spence).

Structure of the Mammary Gland

The gland is composed of:

1.​ Skin​

○​ Includes the nipple, usually at the level of the 4th intercostal space, and​

○​ The areola, a pigmented area surrounding the nipple​

2.​ Parenchyma (Glandular Tissue)​

○​ Made up of 15–20 lobes, each draining into a lactiferous duct​

○​ Each duct opens separately on the nipple and is preceded by a

lactiferous sinus (dilated portion for milk storage)​

3.​ Stroma​

○​ Contains fibrous connective tissue and fat​

 ○​ Fibrous tissue forms suspensory ligaments (of Cooper) that support the
breast by attaching to the skin​

Histology
●​ Each lobe consists of multiple lobules, which are made up of alveoli​

●​ The alveoli are lined by secretory epithelial cells and surrounded by

myoepithelial cells​

●​ During lactation, alveoli actively secrete milk, which is transported via ducts to
the nipple​

Blood Supply
●​ Arterial supply:​

○​ Internal thoracic artery (medial mammary branches)​

○​ Lateral thoracic artery (from axillary artery)​

○​ Thoracoacromial artery​

○​ Posterior intercostal arteries​

●​ Venous drainage:​

○​ Corresponds to the arteries and drains into axillary and internal thoracic
veins​

Lymphatic Drainage
●​ Axillary nodes (especially anterior group): ~75% of lymph drains here​
 ●​ Parasternal (internal mammary) nodes: important for medial breast​

●​ Interpectoral (Rotter's) nodes​

●​ Subdiaphragmatic and subclavicular nodes (small contribution)​

Lymphatic drainage is clinically significant in breast cancer spread.

Nerve Supply
●​ Derived from the anterior and lateral cutaneous branches of 2nd to 6th
intercostal nerves​

●​ These nerves carry sensory fibers to the skin and sympathetic fibers to blood
vessels and smooth muscles of the nipple​

Functions of the Mammary Gland

1.​ Milk Secretion​
The gland synthesizes and secretes milk during lactation to provide nourishment
to the newborn.​

2.​ Milk Ejection​

The myoepithelial cells surrounding alveoli contract in response to oxytocin,
aiding milk ejection.​

3.​ Endocrine Response​

The gland responds to hormonal stimuli from prolactin (milk production) and
oxytocin (milk let-down reflex).​

4.​ Immune Protection​

Colostrum and breast milk contain IgA antibodies and other immune factors
that protect the infant.​
Development of the Mammary Gland
●​ Originates from the mammary ridge (milk line), an ectodermal thickening​

●​ Develops in both sexes, but under the influence of estrogen and progesterone,
it matures in females during puberty​

Changes in Mammary Gland

1.​ Puberty​
Gland enlarges under hormonal influence, ductal system develops​

2.​ Pregnancy​

○​ Glandular tissue proliferates​

○​ Alveoli and ducts increase in number and size​

○​ Colostrum is secreted in late pregnancy​

3.​ Lactation​

○​ Milk production begins post-delivery under influence of prolactin​

○​ Oxytocin helps with milk ejection reflex​

4.​ Post-Menopause​

○​ Glandular tissue atrophies​

○​ Fibrofatty tissue increases​

Applied Anatomy (Clinical Significance)
1.​ Carcinoma of the Breast​

○​ Most common cancer in females​

○​ Common signs: retraction of nipple, peau d’orange appearance, lump in

upper outer quadrant​

○​ Spreads via lymphatics and blood

2.​ Mastitis​

○​ Infection of the breast tissue, often in lactating women​

○​ Presents with pain, redness, and fever​

3.​ Gynecomastia​

○​ Enlargement of male breast tissue​

○​ Caused by hormonal imbalance, liver disease, or drug side effects​

4.​ Fibrocystic Changes​

○​ Benign condition involving lumpiness, pain, and tenderness in breasts​

○​ Usually related to menstrual cycle​

5.​ Paget’s Disease of the Nipple​

○​ A rare form of breast cancer that begins in the ducts and extends to the
nipple​
Definition
Epithelial tissue is a type of tissue that forms the covering or lining of body
surfaces, cavities, and hollow organs. It also forms glands. It consists of closely
packed cells with minimal intercellular substance and lies on a basement membrane.

Characteristics of Epithelial Tissue

1.​ Cellularity​
The tissue is composed almost entirely of cells with minimal extracellular matrix.​

2.​ Polarity​
Cells have an apical surface (free), a lateral surface (in contact with adjacent
cells), and a basal surface (attached to the basement membrane).​

3.​ Avascularity​
Epithelial tissues lack blood vessels and receive nutrition by diffusion from
underlying connective tissue.​

4.​ Basement Membrane​

A non-cellular layer separating epithelium from connective tissue; it supports and
anchors the epithelium.​

5.​ Regeneration​
Epithelial cells have a high rate of mitosis, allowing rapid regeneration.​

6.​ Innervation​
Although avascular, it is often richly innervated by sensory nerve endings.​

Classification of Epithelial Tissue

Epithelia are classified based on:

●​ Number of layers​

●​ Shape of cells​
A. Based on Number of Layers

1.​ Simple Epithelium​

A single layer of cells, all in contact with the basement membrane.​
Function: absorption, secretion, diffusion​

2.​ Stratified Epithelium​

Multiple layers of cells, only the deepest layer touches the basement
membrane.​
Function: protection against mechanical stress​

3.​ Pseudostratified Epithelium​

Appears layered due to varying cell heights, but all cells touch the basement
membrane.​

4.​ Transitional Epithelium (Urothelium)​

Specialized stratified epithelium found in urinary tract, capable of stretching.​

B. Based on Cell Shape

1.​ Squamous – flat, thin cells​

2.​ Cuboidal – cube-like, equal height and width​

3.​ Columnar – tall, rectangular cells​

Types of Epithelium with Examples

Type Location Function

Simple squamous Alveoli, endothelium Diffusion, filtration

Simple cuboidal Kidney tubules, thyroid Secretion, absorption

follicles

Simple columnar Stomach, intestine Absorption, secretion

(non-ciliated)
Simple columnar (ciliated) Uterine tubes, small Movement of
bronchi mucus/ovum

Pseudostratified columnar Respiratory tract (trachea, Mucus secretion and

(ciliated) bronchi) clearance

Stratified squamous Skin (epidermis) Protection from

(keratinized) abrasion

Stratified squamous Esophagus, oral cavity Protection in moist

(non-keratinized) areas

Transitional Urinary bladder, ureters Stretching to hold urine

Functions of Epithelial Tissue

1.​ Protection​
Stratified epithelium protects underlying tissues from physical and chemical
damage.​

2.​ Absorption​
Simple columnar epithelium in the intestines absorbs nutrients.​

3.​ Secretion​
Glandular epithelium secretes enzymes, mucus, hormones, etc.​

4.​ Excretion​
Renal tubules lined with epithelium help in excretion of waste products.​

5.​ Diffusion​
Simple squamous epithelium facilitates exchange of gases in alveoli.​

6.​ Filtration​
Endothelial lining in kidneys allows filtration of blood.​

7.​ Sensory Reception​

Specialized epithelial cells in organs like the nose and tongue detect stimuli.
8.​ Movement​
Ciliated epithelium in the respiratory tract moves mucus and trapped particles.​
Specializations of the Epithelium
1.​ Cilia​
Motile extensions that help in the movement of particles (e.g., in the trachea)​

2.​ Microvilli​
Increase surface area for absorption (e.g., in small intestine)​

3.​ Stereocilia​
Long, non-motile projections found in the epididymis and inner ear​

4.​ Keratinization​
Surface cells accumulate keratin for protection (e.g., skin)​

Glandular Epithelium
Glands are formed by epithelial cells that specialize in secretion. They are classified as:

A. Based on Route of Secretion

●​ Exocrine glands: with ducts (e.g., salivary glands)​

●​ Endocrine glands: ductless, secrete into blood (e.g., pituitary gland)​

●​ Mixed (amphicrine): both functions (e.g., pancreas)​

B. Based on Mode of Secretion

●​ Merocrine – secretion by exocytosis (e.g., sweat glands)​

●​ Apocrine – part of the cell is shed (e.g., mammary glands)​

●​ Holocrine – whole cell disintegrates (e.g., sebaceous glands)​

Clinical Correlations
1.​ Metaplasia​
Change in type of epithelial cells due to stress or injury (e.g., respiratory tract
epithelium changes from ciliated to squamous in smokers)​

2.​ Carcinoma​
Malignant tumors of epithelial origin; common in skin, breast, colon, etc.​

3.​ Cystic Fibrosis​

Dysfunction in epithelial chloride channels affects mucus-secreting epithelia,
especially in the lungs and pancreas​

4.​ Peptic Ulcer​

Damage to the protective epithelial lining of the stomach/duodenum leads to
ulcer formation​
Definition
The elbow joint is a complex synovial hinge joint formed between the lower end of
the humerus and the upper ends of the radius and ulna. It allows movements of flexion
and extension of the forearm.

Type of Joint
It is a composite joint made up of three articulations enclosed in a single synovial
capsule:

●​ Humeroulnar joint – a true hinge joint​

●​ Humeroradial joint – a ball-and-socket type joint​

●​ Proximal radioulnar joint – a pivot joint

Articulating Bones
1.​ Humerus: lower end​

○​ Trochlea (medially)​

○​ Capitulum (laterally)​

2.​ Ulna: upper end​

○​ Trochlear notch​

○​ Olecranon and coronoid processes​

3.​ Radius: upper end​

○​ Head of the radius articulates with the capitulum of the humerus​

○​ Also participates in the proximal radioulnar joint

Articular Surfaces
1.​ Humeroulnar Joint​

○​ Trochlea of humerus with trochlear notch of ulna​

2.​ Humeroradial Joint​

○​ Capitulum of humerus with head of radius​

3.​ Proximal Radioulnar Joint​

○​ Head of radius with radial notch of ulna (pivot movement)

Ligaments of the Elbow Joint

1.​ Capsular Ligament​

○​ Encloses the joint and is attached to the margins of articular surfaces​

2.​ Ulnar Collateral Ligament (Medial)​

○​ Extends from the medial epicondyle of the humerus to the coronoid and
olecranon process of the ulna​

3.​ Radial Collateral Ligament (Lateral)​

○​ Extends from the lateral epicondyle of the humerus and blends with the
annular ligament of the radius​

4.​ Annular Ligament​

○​ Encircles the head of the radius and holds it against the radial notch of the
ulna
Movements of the Elbow Joint
Movements occur mainly at the humeroulnar and humeroradial joints:

1.​ Flexion​

○​ Bending the forearm towards the arm​

○​ Muscles: Brachialis, biceps brachii, brachioradialis​

2.​ Extension​

○​ Straightening the forearm​

○​ Muscle: Triceps brachii​

Note: The proximal radioulnar joint allows pronation and supination, but these are not
considered elbow joint movements directly.

Relations of the Elbow Joint

Anteriorly

●​ Median nerve​

●​ Brachial artery​

●​ Biceps tendon​

Posteriorly

●​ Olecranon process​

●​ Triceps tendon​
Medially

●​ Ulnar nerve (posterior to medial epicondyle)​

Laterally

●​ Radial nerve and common extensor origin

Blood Supply
●​ Derived from the anastomosis around the elbow joint​
(branches of brachial, radial, and ulnar arteries)​

Nerve Supply
The joint is innervated by the following nerves:

●​ Musculocutaneous nerve​

●​ Radial nerve​

●​ Median nerve​

●​ Ulnar nerve​

Stability of the Joint

The elbow joint is a stable joint due to:

1.​ Interlocking of the trochlea and trochlear notch​

2.​ Strong collateral ligaments​

3.​ Muscular support, especially triceps and brachialis​

Applied Anatomy / Clinical Correlations
1.​ Dislocation of the Elbow​

○​ Common in children due to falls on an outstretched hand. Posterior

dislocation is most frequent.​

2.​ Pulled Elbow (Nursemaid’s Elbow)​

○​ Subluxation of the radial head in young children, due to sudden pull on the
forearm​

3.​ Supracondylar Fracture​

○​ Common in children, may damage the brachial artery and median nerve​

4.​ Tennis Elbow (Lateral Epicondylitis)​

○​ Inflammation of the common extensor origin, causing pain over the

lateral epicondyle​

5.​ Golfer’s Elbow (Medial Epicondylitis)​

○​ Inflammation of the common flexor origin, leading to pain over the

medial epicondyle​

.
Definition
The radial artery is one of the two terminal branches of the brachial artery, beginning
at the level of the neck of the radius and ending in the deep palmar arch of the hand.
It mainly supplies the lateral (thumb) side of the forearm and hand.

Origin
●​ Arises in the cubital fossa, at the level of the neck of the radius, as a terminal
branch of the brachial artery.

Course
1.​ Forearm:​

○​ Descends on the lateral side of the forearm, superficial throughout most

of its course.​

○​ Lies lateral to the flexor carpi radialis tendon near the wrist.​

○​ Common site for palpation of the radial pulse.​

2.​ Wrist and Hand:​

○​ Winds around the lateral aspect of the wrist and passes through the
anatomical snuff box.​

○​ Enters the palm by piercing between the two heads of the first dorsal
interosseous muscle and contributes to the deep palmar arch.

Branches
In the Forearm:

1.​ Radial recurrent artery – anastomoses with the radial collateral artery.​

2.​ Muscular branches – supply adjacent muscles.​

 3.​ Palmar carpal branch – joins the palmar carpal arch.​

4.​ Superficial palmar branch – may join the superficial palmar arch.​

In the Hand:

5.​ Dorsal carpal branch – helps form the dorsal carpal arch.​

6.​ First dorsal metacarpal artery​

7.​ Princeps pollicis artery – main artery of the thumb.​

8.​ Radialis indicis artery – supplies the lateral side of the index finger.​

9.​ Deep palmar arch – terminal branch, formed by anastomosing with the deep
branch of the ulnar artery.​

Relations
●​ Anteriorly: Skin, superficial fascia, and radial pulse point​

●​ Medially: Flexor carpi radialis tendon (in the distal forearm)​

●​ Laterally: Brachioradialis muscle in the upper part of forearm​

Clinical Importance
1.​ Radial Pulse​

○​ Easily palpated on the anterior wrist, lateral to flexor carpi radialis.

Common site to check pulse rate.​

2.​ Arterial Grafts​

○​ Radial artery may be used as a graft in coronary artery bypass surgery.​

3.​ Allen’s Test​

○​ Performed before radial artery cannulation to assess the patency of ulnar

artery and ensure adequate collateral circulation.​

4.​ Arterial Blood Sampling or Line Insertion​

○​ Radial artery is a common site for arterial blood gas (ABG) sampling.​
Definition
The ulnar artery is the larger of the two terminal branches of the brachial artery,
primarily supplying the medial (ulnar) side of the forearm and hand, including the
superficial palmar arch.

Origin
●​ Arises in the cubital fossa, at the level of the neck of the radius, as a terminal
branch of the brachial artery, alongside the radial artery.

Course
In the Forearm

●​ Initially lies deep to the ulnar head of the pronator teres muscle.​

●​ Then descends deep to the flexor carpi ulnaris along with the ulnar nerve.​

●​ Becomes superficial in the lower one-third of the forearm.​

At the Wrist and Hand

●​ Enters the palm superficial to the flexor retinaculum, lateral to the pisiform
bone and medial to the ulnar nerve.​

●​ Forms the superficial palmar arch, which is the main arterial supply to the palm
and fingers.

Branches
In the Forearm

1.​ Anterior ulnar recurrent artery – anastomoses with the inferior ulnar collateral
artery.​
 2.​ Posterior ulnar recurrent artery – anastomoses with the superior ulnar
collateral artery.​

3.​ Common interosseous artery (short trunk giving rise to):​

○​ Anterior interosseous artery​

○​ Posterior interosseous artery​

4.​ Muscular branches – to adjacent muscles​

At the Wrist and Palm

5.​ Palmar carpal branch – helps form palmar carpal arch​

6.​ Dorsal carpal branch – contributes to dorsal carpal arch​

7.​ Superficial palmar branch – continues as the superficial palmar arch​

8.​ Deep branch – joins the deep palmar arch from the radial artery

Relations
●​ Medial: Ulnar nerve (in the distal forearm and at the wrist)​

●​ Anterior: Covered by skin, fascia, and flexor carpi ulnaris tendon (in lower part)​

●​ Posterior: Lies on flexor digitorum profundus and pronator quadratus​

Surface Anatomy
The ulnar artery runs from a point 1 cm below the bend of the elbow to a point just
lateral to the pisiform bone in the wrist.
Clinical Importance
1.​ Superficial Palmar Arch​

○​ Ulnar artery is the main contributor; injury may severely impair blood
supply to the fingers.​

2.​ Pulse Palpation​

○​ Ulnar pulse is less prominent and difficult to palpate compared to the

radial artery.​

3.​ Cannulation / Blood Sampling​

○​ Rarely used due to its deeper location and proximity to the ulnar nerve.​

4.​ Allen’s Test​

○​ Confirms ulnar artery patency before procedures like radial artery

cannulation or harvesting.​
Definition
The cubital fossa is a triangular depression located on the anterior aspect of the
elbow, serving as an important transitional area between the arm and forearm.

Boundaries
1. Superior (Base)

●​ An imaginary line drawn between the medial and lateral epicondyles of the
humerus.​

2. Medial Boundary

●​ Lateral border of pronator teres muscle​

3. Lateral Boundary

●​ Medial border of brachioradialis muscle​

4. Apex

●​ Formed inferiorly by the meeting point of pronator teres and brachioradialis

muscles.​

5. Roof

●​ Formed by:​

○​ Skin​

○​ Superficial fascia (containing median cubital vein, lateral and medial

cutaneous nerves of the forearm)​
 ○​ Deep fascia reinforced by the bicipital aponeurosis​

6. Floor

●​ Formed by:​

○​ Brachialis muscle (medially)​

○​ Supinator muscle (laterally)​

Contents of Cubital Fossa (from lateral to medial)

A handy mnemonic: TAN

●​ T – Tendon of biceps brachii​

●​ A – Brachial artery (and its bifurcation into radial and ulnar arteries)​

●​ N – Median nerve​

👉 Behind the brachioradialis (not within the fossa but nearby): Radial nerve (divides
into superficial and deep branches here)

Clinical Importance
1. Venipuncture Site

●​ The median cubital vein, located in the superficial fascia, is commonly used for
drawing blood, IV cannulation, and transfusion due to its superficial location and
minimal discomfort.​

2. Blood Pressure Measurement

●​ The brachial artery is palpated or auscultated here when measuring blood

pressure.​
3. Arterial Cannulation or Catheterization

●​ Brachial artery access for procedures like arteriography or intra-arterial blood

gas sampling.​

4. Nerve Injuries

●​ Trauma to the cubital fossa can damage the median nerve, leading to motor and
sensory deficits in the forearm and hand.​

5. Supracondylar Fractures of Humerus

●​ A common injury in children, which may damage the contents of the cubital
fossa, especially the brachial artery and median nerve, potentially leading to
Volkmann’s ischemic contracture.
Definition
Pectoralis major is a large, thick, fan-shaped superficial muscle of the chest, primarily
responsible for movements of the shoulder joint.

Origin
The muscle has three heads with distinct origins:

1.​ Clavicular head:​

○​ Originates from the anterior surface of the medial half of the clavicle.​

2.​ Sternocostal head:​

○​ Arises from the anterior surface of the sternum and the upper six
costal cartilages.​

3.​ Abdominal head:​

○​ Originates from the aponeurosis of the external oblique muscle of the

anterior abdominal wall.​

Insertion
●​ All three heads converge into a thick, flat tendon that inserts into the lateral lip
of the bicipital (intertubercular) groove of the humerus.​

Nerve Supply
●​ Lateral pectoral nerve (C5, C6, C7)​

●​ Medial pectoral nerve (C8, T1)​

Actions
1.​ Adduction of the arm at the shoulder joint.​

2.​ Medial rotation of the humerus.​

3.​ Flexion of the arm (mainly clavicular head).​

4.​ Extension of the flexed arm (mainly sternocostal head).​

5.​ Assists in forced inspiration by elevating the ribs when the arm is fixed.​

Relations
●​ Superficial: Skin and superficial fascia of the chest.​

●​ Deep: Pectoralis minor lies deep to the lower part of pectoralis major.​

●​ Lateral: Deltoid muscle.​

Blood Supply
●​ Primarily from the pectoral branch of the thoracoacromial artery.​

●​ Additional supply from the lateral thoracic artery and internal thoracic artery.​

Clinical Significance
1.​ Muscle tears or strain: Common in athletes during activities involving forceful
arm movements.​

2.​ Pectoralis major flap: Used in reconstructive surgeries of the chest wall.​

3.​ Winged scapula differential: Helps differentiate between pectoralis major injury
and serratus anterior palsy.​
Definition
The deltoid is a thick, triangular-shaped muscle that forms the rounded contour of the
shoulder. It is the prime mover for shoulder abduction after the initial 15 degrees.

Origin
The deltoid muscle has three distinct parts, each with a separate origin:

1.​ Clavicular (anterior) part:

○​ Arises from the lateral third of the clavicle.​

2.​ Acromial (middle) part:

○​ Originates from the acromion process of the scapula.​

3.​ Spinal (posterior) part:

○​ Originates from the spine of the scapula.​

Insertion
●​ All three parts converge to insert into the deltoid tuberosity on the lateral aspect
of the humerus.

Nerve Supply
●​ Innervated by the axillary nerve (C5, C6).

Blood Supply
●​ Mainly by the posterior circumflex humeral artery and deltoid branch of the
thoracoacromial artery.
Actions
1.​ Clavicular (anterior) part:
○​ Flexes and medially rotates the arm at the shoulder joint.​

2.​ Acromial (middle) part:

○​ Primary abductor of the arm from 15° to 90°.​

3.​ Spinal (posterior) part:

○​ Extends and laterally rotates the arm.​

Relations
●​ Superficial: Skin and superficial fascia over the shoulder.​

●​ Deep: Lies over the rotator cuff muscles (supraspinatus, infraspinatus, teres
minor).
●​ Anteriorly: Clavipectoral fascia and pectoralis major.​

●​ Posteriorly: Trapezius muscle.​

Clinical Significance
1.​ Axillary nerve injury:​

○​ Can occur with shoulder dislocation or humeral surgical neck fracture,

leading to deltoid paralysis and loss of shoulder abduction.​

2.​ Intramuscular injections:​

○​ The deltoid is a common site for intramuscular injections due to its

accessibility and thickness.​
Definition
Cartilage is a specialized, semi-rigid connective tissue that provides flexible support and
reduces friction between bony surfaces in joints.

Structure
Cartilage is composed of cells called chondrocytes embedded in an extracellular
matrix made up of collagen fibers, proteoglycans, and water. It lacks blood vessels
(avascular) and nerves.

Types of Cartilage
1. Hyaline Cartilage

●​ Most abundant type.​

●​ Has a glassy, translucent appearance.​

●​ Found in articular surfaces of bones, nose, trachea, larynx, and the embryonic
skeleton.​

●​ Function: Provides smooth surfaces for joint movement and support with some
flexibility.

2. Elastic Cartilage

●​ Contains numerous elastic fibers, making it more flexible.​

●​ Found in the external ear (auricle), epiglottis, and auditory tube.​

●​ Function: Provides flexible support and maintains shape.

3. Fibrocartilage

●​ Dense bundles of collagen fibers, very tough and resistant to compression.​

 ●​ Found in intervertebral discs, pubic symphysis, menisci of the knee, and tendon
insertions.​

●​ Function: Acts as a shock absorber and provides tensile strength.

Physiology and Functions

1.​ Support and Shape​
Cartilage maintains the shape of structures like the ear and nose and supports
soft tissues.​

2.​ Smooth Articular Surfaces​

Hyaline cartilage covers joint surfaces, reducing friction and facilitating smooth
movement.​

3.​ Shock Absorption​

Fibrocartilage absorbs mechanical shocks in weight-bearing joints.​

4.​ Growth and Development​

In the fetus, cartilage forms the initial skeleton, which is later replaced by bone
(endochondral ossification).​

5.​ Flexibility with Strength​

Elastic cartilage provides flexibility without sacrificing structural integrity.​

6.​ Protection of Bones​

Cartilage cushions bones against mechanical stress.​

Nutrition and Repair

●​ Cartilage receives nutrients by diffusion from surrounding tissues due to its avascular
nature.​

●​ Limited repair capability because of the absence of blood vessels.​

Clinical Significance
1.​ Osteoarthritis​

○​ Degeneration of articular hyaline cartilage causes joint pain and stiffness.​

2.​ Chondromalacia Patellae​

○​ Softening and damage to cartilage beneath the kneecap, causing pain.​

3.​ Cartilage Injuries​

○​ Poor healing due to avascularity; often requires surgical intervention.​

Definition
The median nerve is a major peripheral nerve of the upper limb that provides motor and
sensory innervation to parts of the forearm and hand.

Origin
●​ Formed by the union of the lateral and medial cords of the brachial plexus.​

●​ Contains nerve fibers from spinal nerve roots C5, C6, C7, C8, and T1.

Course
1.​ In the arm:​

○​ Runs medial to the brachial artery in the anterior compartment.​

○​ Does not give any branches in the arm.​

2.​ At the cubital fossa:​

○​ Passes anterior to the elbow joint, lying medial to the brachial artery.​

3.​ In the forearm:​

○​ Enters between the two heads of the pronator teres muscle.​

○​ Runs between the flexor digitorum superficialis and profundus muscles.​

○​ Gives motor branches to most of the anterior forearm muscles.​

4.​ In the wrist and hand:​

○​ Passes through the carpal tunnel into the palm.​

○​ Divides into sensory and motor branches in the hand.​

Branches
1. Muscular branches

●​ Innervate most of the flexor muscles in the forearm (except flexor carpi ulnaris
and medial half of flexor digitorum profundus).​

●​ Supplies the thenar muscles and the first two lumbricals in the hand.

2. Palmar cutaneous branch

●​ Arises in the forearm and supplies skin over the thenar eminence (palm).

3. Digital branches

●​ Provide sensation to the lateral 3.5 fingers (thumb, index, middle, and lateral half
of ring finger) on the palmar side.

Functions
1.​ Motor function:​

○​ Controls flexion of the wrist and fingers (except those supplied by ulnar
nerve).​

○​ Controls thumb opposition and abduction via thenar muscles.​

2.​ Sensory function:​

○​ Provides sensation to the palmar side of the lateral 3.5 fingers and distal
dorsal fingertips.

Clinical Significance
1.​ Carpal Tunnel Syndrome:​

○​ Compression of the median nerve under the flexor retinaculum causes

pain, numbness, and weakness in the hand, especially the thumb and first
two fingers.​
2.​ Pronator Teres Syndrome:​

○​ Compression of the nerve between the two heads of pronator teres

causes forearm pain and paresthesia.​

3.​ Injury at the elbow:​

○​ Can cause "ape hand" deformity (inability to oppose the thumb) and loss
of sensation in the lateral palm.​
Definition
The median nerve is a major peripheral nerve of the upper limb that provides motor and
sensory innervation to parts of the forearm and hand.

Origin
●​ Formed by the union of the lateral and medial cords of the brachial plexus.​

●​ Contains nerve fibers from spinal nerve roots C5, C6, C7, C8, and T1.​

Course
1.​ In the arm:​

○​ Runs medial to the brachial artery in the anterior compartment.​

○​ Does not give any branches in the arm.​

2.​ At the cubital fossa:​

○​ Passes anterior to the elbow joint, lying medial to the brachial artery.​

3.​ In the forearm:​

○​ Enters between the two heads of the pronator teres muscle.​

○​ Runs between the flexor digitorum superficialis and profundus muscles.​

○​ Gives motor branches to most of the anterior forearm muscles.​

4.​ In the wrist and hand:​

○​ Passes through the carpal tunnel into the palm.​

○​ Divides into sensory and motor branches in the hand.​

Branches
1. Muscular branches

●​ Innervate most of the flexor muscles in the forearm (except flexor carpi ulnaris
and medial half of flexor digitorum profundus).​

●​ Supplies the thenar muscles and the first two lumbricals in the hand.​

2. Palmar cutaneous branch

●​ Arises in the forearm and supplies skin over the thenar eminence (palm).​

3. Digital branches

●​ Provide sensation to the lateral 3.5 fingers (thumb, index, middle, and lateral half
of ring finger) on the palmar side.

Functions
1.​ Motor function:
○​ Controls flexion of the wrist and fingers (except those supplied by ulnar
nerve).​

○​ Controls thumb opposition and abduction via thenar muscles.​

2.​ Sensory function:

○​ Provides sensation to the palmar side of the lateral 3.5 fingers and distal
dorsal fingertips.

Clinical Significance
1.​ Carpal Tunnel Syndrome:​
Compression of the median nerve under the flexor retinaculum causes pain,
numbness, and weakness in the hand, especially the thumb and first two fingers.​
2.​ Pronator Teres Syndrome:​
Compression of the nerve between the two heads of pronator teres causes
forearm pain and paresthesia.​

3.​ Injury at the elbow:​

Can cause "ape hand" deformity (inability to oppose the thumb) and loss of
sensation in the lateral palm.