The Upper Limbs – Anatomy, Structure, Functions

Last updated: February 8, 2026Reviewed date: February 8, 2026Reading time: 9 min read
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The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist, and knuckle joints. In humans, each upper limb is divided into the arm, forearm and hand, and is primarily used for climbing, lifting, and manipulating objects. Humerus (The Upper Arm) The bone-forming upper arm is the humerus. The humerus is a long bone in the arm that...

For severe symptoms, danger signs, pregnancy, child illness, or sudden worsening, seek urgent medical care.

বাংলা রোগী নোট এখনো যোগ করা হয়নি। পোস্ট এডিটরে “RX Bangla Patient Mode” বক্স থেকে সহজ বাংলা সারাংশ যোগ করুন।

এই তথ্য শিক্ষা ও সচেতনতার জন্য। এটি ডাক্তারি পরীক্ষা, রোগ নির্ণয় বা প্রেসক্রিপশনের বিকল্প নয়।

Article Summary

The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist, and knuckle joints. In humans, each upper limb is divided into the arm, forearm and hand, and is primarily used for climbing, lifting, and manipulating objects. Humerus (The Upper Arm) The bone-forming upper arm is the humerus. The humerus is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius, and the ulna, and consists...

Key Takeaways

  • This article explains Humerus (The Upper Arm) in simple medical language.
  • This article explains Ulna and Radius (The Forearm) in simple medical language.
  • This article explains Carpals, Metacarpals, and Phalanges (The Hand) in simple medical language.
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Definition

The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist, and knuckle joints. In humans, each upper limb is divided into the arm, forearm and hand, and is primarily used for climbing, lifting, and manipulating objects.

Humerus (The Upper Arm)

The bone-forming upper arm is the humerus. The humerus is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius, and the ulna, and consists of three sections. The humeral upper extremity consists of a rounded head, a narrow neck, and two short processes (tubercles, sometimes called tuberosities). The body is cylindrical in its upper portion, and more prismatic below. The lower extremity consists of 2 epicondyles, 2 processes (trochlea & capitulum), and 3 fossae (radial fossa, coronoid fossa, and olecranon fossa). As well as its true anatomical neck, the constriction below the greater and lesser tubercles of the humerus is referred to as its surgical neck due to its tendency to fracture, thus often becoming the focus of surgeons.

Key Points

The humerus articulates with the scapula at the shoulder and with the radius and ulna at the elbow.

The humerus is typically described as having a proximal region, shaft, and distal region.

Both the anatomical and surgical neck of the humerus are highly susceptible to fracture.

Key Terms

humerus: The bone of the upper arm.

surgical neck: A constriction below the tubercles of the greater tubercle and lesser tubercle.

capitulum: At the distal head of the humerus, it articulates with the radius of the forearm.

trochlea: At the distal head of the humerus, it articulates with the ulna of the forearm.

anatomical neck: A constriction adjacent to the humeral head that increases the range of movement possible at the shoulder joint.

The humerus is a bone in the upper arm. It runs from the shoulder to the elbow. Proximally it articulates with the scapula to form the shoulder joint, or glenohumeral joint. Distally, the humerus articulates with the radius and ulna to form the elbow joint.

The Upper Limbs - Anatomy, Structure, Functions

Humerus: The humerus attaches proximally to the scapula (shoulderblade) at the humeral head and distally with the radius and ulna (lower-arm bones) at the trochlea and capitulum, respectively.

The proximal portion of the humerus can be divided into three parts.

  • The rounded humeral head projects medially and articulates with the glenoid cavity of the scapula.
  • Immediately adjacent to the head is the narrower anatomical neck, which allows for a wider range of movements of the head within the shoulder joint.
  • Finally, the greater and lesser tubercles are found at the most superior end of the main shaft of the humerus.

The four rotator cuff muscles attach to these tubercles, strengthening and maintaining the shoulder joint. Between the two tubercles lies a deep grove called the intertubercular sulcus, through which the tendon of the long head of the biceps brachii runs.

Below this proximal region lies the shaft, which is separated from the proximal region by the surgical neck, so-termed as this in an area of the frequent fracture. A major feature of the shaft is the deltoid tuberosity located laterally to which the deltoid muscle attaches.

The deltoid, coracobrachialis, brachialis, and brachioradialis muscles attach to the anterior surface, with the triceps brachii attaching to the posterior.

Distally, the humerus flattens to articulate with the ulna and radius at the elbow joint. The medially located trochlea articulates with the ulna. Located laterally to this is the capitulum that articulates with the radius.

Several muscles of the forearm responsible for an extension at the wrist attach to the humerus immediately above the capitulum and trochlea.

Ulna and Radius (The Forearm)

The forearm contains two bones, the radius, and the ulna.

Key Points

The radius and the ulna are long, slightly curved bones that lie parallel from the elbow, where they articulate with the humerus, to the wrist, where they articulate with the carpals.

The radius is located laterally, near the thumb, and the ulna medially, near the little finger. The radius and the ulna have a styloid process at the distal end; they are also attachment sites for many muscles.

The radius is smaller than the ulna.

Key Terms

radius: One of two forearm bones, it is located laterally to the ulna.

ulna: One of two forearm bones, it is located medially to the radius.

The Upper Limbs - Anatomy, Structure, Functions

The forearm: The radius and ulna are the bones of the forearm.

The forearm contains two bones—the radius and the ulna—that extend in parallel from the elbow, where they articulate with the humerus to the wrist, where they articulate with the carpals. The space between the two bones is spanned by the interosseous membrane.

The Ulna

Anatomically, the ulna is located medially to the radius, placing it near the little finger. The ulna is slightly larger than the radius.

Proximally, there are five key regions of the ulna:

  • The olecranon is a projection of bone that extends proximally from the ulna.
  • The triceps brachii muscle attaches to the ulna superiorly.
  • The cornoid process, together with the olecranon, forms the trochlear notch where it articulates with the trochlea of the humerus.
  • Laterally to the trochlear notch lies the radial notch, which articulates with the head of the radius to form the proximal radioulnar joint.
  • Immediately distal to the coronoid process is the tuberosity of ulna, to which the brachialis muscle attaches.

The shaft of the ulna is triangular and numerus muscles involved in pronation and flexion of the forearm attach to its surface.

Distally, the ulna is much smaller and terminates with a rounded head that articulates with the ulnar notch of the radius to form the distal radioulnar joint. The styloid process of the ulna extends distally and is the site of attachment for ligaments found in the wrist.

The Radius

Anatomically, the radius is located laterally to the ulna placing it near the thumb. The radius is slightly smaller than the ulna and pivots around the ulna to produce movement at the proximal and distal radioulnar joints.

Proximally, the radius terminates with a disk-shaped head that articulates with the capitulum of the humerus and the radial notch of the ulna. Immediately below the head lies the radial tuberosity to which the biceps brachii attaches. As with the ulna, the shaft of the radius is triangular in shape and numerous muscles, including the protonator teres, attach to it.

Distally the radius expands, medially the ulnar notch articulates with the head of the ulnar. Immediately adjacent to the ulnar notch, the radius articulates with the scaphoid and lunate carpal bones to form part of the wrist.

Carpals, Metacarpals, and Phalanges (The Hand)

Each hand consists of 27 bones, divided between the wrist bones (carpals), the palm bones (metacarpals), and the finger bones (phalanges).

Key Points

There are eight carpal bones in each wrist.

There are five metacarpal bones in each hand.

There are proximal, intermediate, and distal phalanges in each digit except for the thumb, which lacks an intermediate phalange.

Key Terms

metacarpal: Any of the bones of the palm.

carpal: Any of the eight bones of the wrist.

phalange: One of the bones of the digits.

The Upper Limbs - Anatomy, Structure, Functions

Carpals of the left hand: There are eight carpal bones in each wrist: scaphoid, lunate, triquetral, pisiform, trapezium, trapezoid, capitate, and hamate.

The hand contains 27 bones. Each one belongs to one of three regions: the carpals, (wrist), the metacarpals, (the palm), and the phalanges (the digits).

Carpals

The eight, irregularly shaped carpals are the most proximal bones of the hand. The carpals are often split into two rows, the proximal row containing the scaphoid, lunate, triquetrum, and pisiform, moving lateral to medial.

The scaphoid and lunate articulate with the radius, and the lunate and triquetrum articulate with the articular disk of the wrist. The pisiform carpal is a sesamoid bone, located within a tendon and is not involved in movement at the wrist.

The distal row contains the trapezium, trapezoid, capitate, and hamate, moving lateral to medial. The trapezium articulates with the scaphoid proximally and the first, thumb, and second metacarpal distally. The trapezoid articulates with the scaphoid proximally and the second metacarpal distally.

The Upper Limbs - Anatomy, Structure, Functions

Metacarpal bones of the left hand: The metacarpals connect the carpal bones of the wrist with the phalanges (finger bones).

The capitate articulates with the scaphoid and lunate proximally and the third and fourth metacarpal. Finally, the hamate articulates with the lunate and triquetral proximally and the fourth and fifth, little finger, metacarpals distally.

Metacarpals

The hand contains five metacarpal bones that articulate proximally with the carpals and distally with the proximal phalanges. They are numbered moving lateral to medial, and start with the thumb, which is metacarpal I, and end with metacarpal V, the little finger.

Each metacarpal consists of a base, shaft, and head, with the concave lateral and medial borders of the shaft allowing attachment of the interossei muscles.

Phalanges

The digits are named in a similar fashion to the metacarpals, moving lateral to medial, and starting at the thumb. With the exception of the thumb, each digit contains a proximal, intermediate, and distal phalange; the thumb lacks an intermediate phalange. The length of the phalanges decreases distally.

Neurovascular system

Nerve supply

Branches of brachial plexus. The motor and sensory supply of the upper limb is provided by the brachial plexus which is formed by the ventral rami of spinal nerves C5-T1. In the posterior triangle of the neck these rami form three trunks from which fibers enter the axilla region (armpit) to innervate the muscles of the anterior and posterior compartments of the limb. In the axilla, cords are formed to split into branches, including the five terminal branches listed below. [rx] The muscles of the upper limb are innervated segmentally proximal to distal so that the proximal muscles are innervated by higher segments (C5–C6) and the distal muscles are innervated by lower segments (C8–T1). [rx]

Motor innervation of the upper limb by the five terminal nerves of the brachial plexus:[rx]

  • The musculocutaneous nerve innervates all the muscles of the anterior compartment of the arm.
  • The median nerve innervates all the muscles of the anterior compartment of the forearm except flexor carpi ulnaris and the ulnar part of the flexor digitorum profundus. It also innervates the three thenar muscles and the first and second lumbricals.
  • The ulnar nerve innervates the muscles of the forearm and hand not innervated by the median nerve.
  • The axillary nerve innervates the deltoid and teres minor.
  • The radial nerve innervates the posterior muscles of the arm and forearm

Collateral branches of the brachial plexus

  • The dorsal scapular nerve innervates rhomboid major, minor, and levator scapulae.
  • The long thoracic nerve innervates serratus anterior.
  • The suprascapular nerve innervates supraspinatus and infraspinatus
  • The lateral pectoral nerve innervates pectoralis major
  • The medial pectoral nerve innervates pectoralis major and minor
  • The upper subscapular nerve innervates subscapularis
  • The thoracodorsal nerve innervates latissimus dorsi
  • The lower subscapular nerve innervates subscapularis and teres major
  • The medial brachial cutaneous nerve innervates the skin of the medial arm
  • The medial antebrachial cutaneous nerve innervates the skin of the medial forearm

Blood supply and drainage

Arteries of the upper limb:

  • The superior thoracic, thoracoacromial, posterior circumflex humeral and subscapular branches of the axillary artery.
  • The deep brachial, superior ulnar collateral, inferior ulnar collateral, radial,

ulnar, nutrient and muscular branches of the brachial artery.

  • The radial recurrent, muscular, superficial palmar, dorsal carpal, princeps pollicis and radialis indicis branches of the radial artery.
  • The anterior ulnar recurrent, posterior ulnar recurrent, anterior interosseous, posterior interosseous and superficial branches of the ulnar artery.

Veins of the upper limb:

  • Basilic vein
  • Cephalic vein
  • Median cubital vein
  • Median antebrachial vein
  • Dorsal venous arch
Doctor visit helper

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A simple rural-patient checklist to help you explain symptoms clearly, ask better questions, and avoid unsafe self-treatment.

Safety note: This is not a prescription or diagnosis. For severe symptoms, pregnancy danger signs, children with serious illness, chest pain, breathing difficulty, stroke-like weakness, or major injury, seek urgent care.

Which doctor may help?

Start with a registered doctor or the nearest qualified health center.

What to tell the doctor

  • Write when the problem started and how it changed.
  • Bring old prescriptions, investigation reports, and current medicines.
  • Write allergies, pregnancy status, diabetes, kidney/liver disease, and major past illnesses.
  • Bring one family member if the patient is weak, elderly, confused, or a child.

Questions to ask

  • What is the most likely cause of my symptoms?
  • Which danger signs mean I should go to hospital quickly?
  • Which tests are necessary now, and which can wait?
  • How should I take medicines safely and what side effects should I watch for?
  • When should I come for follow-up?

Tests to discuss

  • Vital signs: temperature, pulse, blood pressure, oxygen saturation
  • Basic physical examination by a clinician
  • CBC, urine test, blood sugar, or imaging only when clinically needed

Avoid these mistakes

  • Do not use antibiotics, steroid tablets/injections, or strong painkillers without proper medical advice.
  • Do not hide pregnancy, kidney disease, ulcer, allergy, or blood thinner use.
  • Do not delay emergency care when danger signs are present.

Medicine safety and first-aid guide

This section is for patient education only. It does not replace a doctor, pharmacist, or emergency care.

Safe first steps

  • Rest, drink safe water, and observe symptoms carefully.
  • Keep a written note of symptoms, duration, temperature, medicines already taken, and allergy history.
  • Seek medical care quickly if symptoms are severe, worsening, or unusual for the patient.

OTC medicine safety

  • For mild pain or fever, ask a registered pharmacist or doctor before using common over-the-counter pain/fever medicines.
  • Do not combine multiple pain medicines without advice, especially if you have kidney disease, liver disease, stomach ulcer, asthma, pregnancy, or take blood thinners.
  • Do not give adult medicines to children unless a qualified clinician advises it.

Avoid these mistakes

  • Do not start antibiotics without a proper medical decision.
  • Do not use steroid tablets or injections casually for quick relief.
  • Do not delay emergency care because of home remedies.

Get urgent help if

  • Severe symptoms, confusion, fainting, breathing difficulty, chest pain, severe dehydration, or sudden weakness need urgent medical care.
Medicine names, dose, and timing must be decided by a qualified clinician or pharmacist after checking age, pregnancy, allergy, other diseases, and current medicines.

For rural patients and family caregivers

Patient health record and symptom diary

Write your symptoms, medicines already taken, test results, and questions before visiting a doctor. This note stays on your device unless you print or copy it.

Doctor to discuss: Doctor / qualified healthcare provider
Tests to discuss with doctor
  • Basic vital signs: temperature, pulse, blood pressure, oxygen level if needed
  • Relevant blood, urine, imaging, or specialist tests only after clinical assessment
Questions to ask
  • What is the most likely cause of my symptoms?
  • Which warning signs mean I should go to emergency care?
  • Which tests are really needed now?
  • Which medicines are safe for my age, pregnancy status, allergy, kidney/liver/stomach condition, and current medicines?

Emergency warning signs such as chest pain, severe breathing difficulty, sudden weakness, confusion, severe dehydration, major injury, or loss of bladder/bowel control need urgent medical care. Do not wait for online information.

Safe pathway to proper treatment

Care roadmap for: The Upper Limbs – Anatomy, Structure, Functions

Use this simple roadmap to understand the next safe steps. It is educational and does not replace examination by a doctor.

Go to emergency care if you notice:
  • Severe or rapidly worsening symptoms
  • Breathing difficulty, chest pain, fainting, confusion, severe weakness, major injury, or severe dehydration
Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.
  1. Step 1

    Check danger signs first

    If danger signs are present, seek emergency care and do not wait for online information.

  2. Step 2

    Record the symptom story

    Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.

  3. Step 3

    Visit a qualified clinician

    A doctor, nurse, or qualified healthcare provider can examine you and decide which tests or treatment are needed.

  4. Step 4

    Do only useful tests

    Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.

  5. Step 5

    Follow up and return early if worse

    If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips
  • Take a written symptom diary and all previous prescriptions/test reports.
  • Do not hide medicines already taken, even herbal or over-the-counter medicines.
  • Ask which warning signs mean urgent referral to hospital.

This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.

RX Patient Help

Ask a health question safely

Write your symptom story. A health professional or site editor can review it before any answer is prepared. This box is not for emergency care.

Emergency first: Severe chest pain, breathing trouble, unconsciousness, stroke signs, severe injury, heavy bleeding, or rapidly worsening symptoms need urgent local medical care now.

Frequently Asked Questions

Is this article a replacement for a doctor?

No. It is educational content only. Patients should consult a qualified clinician for diagnosis and treatment.

When should I seek urgent care?

Seek urgent care for severe symptoms, rapidly worsening condition, breathing difficulty, severe pain, neurological changes, or any emergency warning sign.

References

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