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Brachialis

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Brachialis

Brachialis

The structure indicated is the brachialis muscle.

The brachialis muscle is one of three muscles in the anterior compartment of the arm:

  1. Biceps brachii
  2. Brachialis
  3. Coracobrachialis

The muscles of the anterior compartment are innervated by the musculocutaneous nerve and generally serve to flex the forearm at the elbow joint.

The brachialis muscle lies deep to the biceps brachii muscle and is synergistic in its action, assisting with flexion of the forearm at the elbow joint.

Origin: Distal half of anterior humerus

Insertion: Ulna tuberosity

Action: Flexion of elbow

Innervation: Musculocutaneous nerve

Learn more about the anatomy of the arm muscles in this tutorial.


Left Coronary Artery

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Left Coronary Artery

Left Coronary Artery

The structure indicated is the left coronary artery.

The left coronary artery (LCA) arises from the left aortic sinus of the ascending aorta. The left coronary artery has two terminal branches:

  • Left anterior descending (LAD)/anterior interventricular
  • Circumflex branch

The left circumflex artery (LCX) supplies blood to the posterolateral left ventricle as well as the anterolateral papillary muscle and provides part of the supply to the left ventricle. The left anterior descending artery also supplies the left ventricle, and is responsible for the arterial supply to the anterolateral myocardium, the apex of the heart and the interventricular septum.

Learn more about the blood supply to the heart in this anatomy tutorial.

Median Antebrachial Vein

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Median Antebrachial Vein

Median Antebrachial Vein

The structure indicated is the median antebrachial vein.

The median antebrachial vein is one of the veins of the superficial venous system of the upper limb. The veins of the upper limb consist of a superficial veins and deep veins. The superficial system consists primarily of the cephalic and basilic veins which originate from the dorsal venous arch and drain into the axillary vein and brachial veins respectively.

In the region of the antecubital fossa, the cephalic vein is joined to the basilic vein via a vein known as the median cubital vein. The median antebrachial vein originates from the palmar venous plexus and is shown in this diagram draining into the basilic vein. There is however a lot of anatomical variation in the configuration of these superficial veins. In some cases the median antebrachial vein may divide into two terminal branches, the median cephalic vein and the median basilic vein which drain into the cephalic and basilic veins respectively.

Learn more about the veins of the body in this anatomy tutorial.

Extensor Digiti Minimi

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Extensor Digiti Minimi

Extensor Digiti Minimi

The structure indicated is the extensor digiti minimi muscle.

The extensor digiti minimi muscle is one of 7 muscles located in the superficial compartment of the posterior forearm. The posterior forearm consists of a superficial and a deep compartment. The superficial compartment contains 7 muscles, whereas the deep compartment contains 5 muscles.

The superficial compartment of the posterior forearm includes the following 7 muscles:

  1. Brachioradialis
  2. Extensor carpi radialis longus
  3. Extensor carpi radialis brevis
  4. Extensor digitorum
  5. Extensor digiti minimi
  6. Extensor carpi ulnaris
  7. Anconeus

The muscles of the posterior compartment of the forearm originate from the lateral epicondyle of the humerus and the supraepicondylar ridge and they are all innervated by the radial nerve and its branches.

Origin: Lateral epicondyle of humerus

Insertion: Extensor expansion of 5th digit at metacarpophalangeal and interphalangeal joints

Action: Extends 5th digit. Weak extensor of wrist

Innervation: Posterior interosseous nerve

 

Learn more about the anatomy of the forearm muscles in this tutorial.

Internal Thoracic Artery

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Internal Thoracic Artery

Internal Thoracic Artery

The structure indicated is the internal thoracic artery.

The internal thoracic artery was formerly known as the internal mammary artery and is an artery located anteriorly in the thorax. It is a branch of the subclavian artery.

The left subclavian artery comes directly off the arch of the aorta, whereas on the right side of the body, the brachiocephalic artery splits, giving rise to the right subclavian artery, and the right common carotid artery.

The subclavian artery becomes the axillary artery at the lateral border of the first rib. It can be thought of in three parts, and gives rise to several branches:

  • First part: vertebral artery, internal thoracic artery, thyrocervical trunk
  • Second part: costocervical trunk
  • Third part: dorsal scapular artery

The internal thoracic arteries descend lateral to the sternum on either side, and give off several branches on the way, including the 12 anterior intercostal branches which anastomose with their counterpart posterior intercostal arteries.

The internal thoracic artery terminates by dividing into two branches: the musculophrenic artery and the superior epigastric artery.

Extensor Digitorum Longus

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Extensor Digitorum Longus

Extensor Digitorum Longus

The structure indicated is the extensor digitorum longus muscle.

The extensor digitorum longus is one of the four muscles of the anterior compartment of the leg. The muscles of the leg consist of three compartments:

  1. Anterior
  2. Posterior
  3. Lateral

In the anterior compartment are the four following muscles:

  1. Tibialis anterior
  2. Extensor hallucis longus
  3. Extensor digitorum longus
  4. Fibularis tertius

The muscles of the anterior compartment of the leg serve to dorsiflex the ankle joint, extend the toes and invert the foot, and they are supplied by the deep fibular (peroneal) nerve.

Origin: Proximal ½ of medial surface of fibula. Lateral tibial condyle.

Insertion: Via 4 tendons into the bases of distal and middle phalanges of lateral four toes.

Action: Extension of lateral four toes. Dorsiflexion of foot.

Innervation: Deep fibular nerve

Learn more about the anatomy of the leg muscles in this tutorial.

Infraspinatus

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Infraspinatus

Infraspinatus

The structure indicated is the infraspinatus muscle of the rotator cuff.

The infraspinatus muscle is one of the four muscles of the rotator cuff. The rotator cuff muscles are located in the posterior scapula region and serve to stabilise the glenohumeral joint. There are 4 rotator cuff muscles which can be remembered using the mnemonic SITS:

  1. Supraspinatus
  2. Infraspinatus
  3. Teres minor
  4. Subscapularis

The supraspinatus and infraspinatus, as their names suggest originate in the fossae above and below the spine of the scapula respectively (supraspinatous and infraspinatous fossae). The supraspinatus, infraspinatus and teres minor muscles insert on to the greater tubercle of the humerus on the superior, middle and inferior facets, in that order.

Origin: Dorsal surface of scapula in infraspinatous fossa (below the spine of the scapula in)

Insertion: Greater tubercle of humerus (middle facet)

Action: Lateral (external) rotation of the humerus. Assists in stabilisation of the glenohumeral joint.

Innervation: Suprascapular nerve.

Learn more about the anatomy of the rotator cuff in this tutorial.

Upper Limb Veins

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Hi, this is Peter from AnatomyZone, and in this tutorial we’re going to be taking a look at the veins of the upper limb. The venous drainage of the upper limb consists of a superficial system which drains to a higher pressure deep venous system.

Read more

The deep veins follow the same course as the arteries of the upper limb. We’ll start by looking at the superficial venous system and we’ll start distally. So looking here at this model of the dorsal aspect of the hand, we can see these paired veins on the dorsal surface of the fingers. These are the dorsal digital veins, and you can see that they unite to form dorsal metacarpal veins, which then drain to this network on the back of the hand – the dorsal venous network.

 

If I rotate the model around to the palmar view, we can see the palmar digital veins. These palmar digital veins join and drain into the dorsal digital veins via small oblique veins, known as the intercapitular branches. I’ve highlighted these intercapitular branches in yellow, and you can see how they drain into the dorsal digital veins on the dorsal surface of the hand.

 

The superficial venous system of the upper limb essentially consists of two main veins, which arise from the dorsal venous network. In green you can see arising laterally from the dorsal venous network, is the cephalic vein, and from the medial aspect of the dorsal venous network, we’ve got the basillic vein, which I’ve highlighted in purple.

 

I’ve just zoomed out a bit and you can see the course of the basilic and cephalic veins. If I rotate around anteirorly, you can see how they curve around anteriorly just before the elbow joint. At the antecubital fossa, the cephalic and basilic veins are joined. There is a lot of anatomical variation from individual to individual and in this model, one particular configuration is shown. So if we look distally again, we can see this venous network on the palm of the hand – this is the palmar venous network and its drained by this vein which runs down the midline of the forearm. This is the median antebrachial vein. So median – middle, ante – in front of, brachial – referring to the arm. So it’s the median antebrachial vein, and in this particular model the median antebrachial vein is shown splitting into two and connecting to the cephalic and basilic veins. These two veins are known as the median cephalic vein and the median basilic vein, respectively. Another common configuration at the antecubital fossa where the cephalic vein drains into the basilic vein directly, is via this vein known as the median cubital vein, and this vein joins the cephalic vein to the basilic vein directly. In this case, the median antebrachial course may take a different course, so it might drain into the basilic vein, rather than forming these two veins – the median cephalic and the median basilic veins. These veins in the antecubital fossa are common sites for venepuncture, as they are large and superficial veins and make good IV access points.

 

I’ve just brought the model a little further proximally, and we can see how the basilic vein runs medially and it pierces the brachial fascia to enter the deep compartment of the arm. I’ve just made this fascial layer transparent, and you can see how the basilic vein drains into the deep brachial veins. The deep brachial veins are paired veins which accompany the brachial artery, and they drain into the axillary vein at the level of the inferior margin of the teres major muscle, which you can see here. Rotating around back anteriorly, let’s take a look at the course of the cephalic vein.

 

After passing above the elbow joint, the cephalic vein ascends lateral to the biceps brachii muscle and you can see here how it passes between the deltoid muscle and the pectoralis major muscle, in what is known as the deltopectoral groove. It then passes into the deltopectoral triangle, which is also known as the clavipectoral triangle, where it pierces the clavipectoral fascia to drain into the axillary vein. The deltopectoral triangle is this triangle that’s bordered by the pectoralis major muscle, the deltoid muscle and the clavicle.

 

As I mentioned before, the axillary vein is a continuation of the brachial vein after the point where the basilic vein drains into it. The axillary vein then becomes the subclavian vein, and the subclavian vein joins the internal jugular vein to drain into the brachiocephalic veins, which are also known as the innominate veins, and the innominate veins, or the right and left brachiocephalic veins drain into the superior vena cava, which then drains into the right atrium of the heart.

 

Now just a few quick notes about the deep venous system of the upper limb. The deep veins of the upper limb follow the arteries, so in the hand you’ve got the superficial and deep palmar venous arches which accompany the corresponding arterial arches. And then coming off these deep venous arches, you’ve got the radial and ulnar veins, which accompany the radial and ulnar arteries of the forearm. These veins which accompany the arteries are known as venae comitantes, which is simply Latin for accompanying veins. Just before the elbow, the radial and ulnar veins unite to form the paired brachial veins, which accompany the brachial artery.

 

If you’d like to get a better idea of the structure and course of the deep venous system, then I’d advise you to watch my previous tutorials on the arterial supply to the upper limb, where I cover this in a lot more detail.

 

So that’s a brief walk through the venous system of the upper limb.


Episode 1 – Muscle Organisation

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Learn all about the organisation of muscle in this brand new physiology tutorial.

Maxilla

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Maxilla

Maxilla

The structure indicated is the maxilla bone.

The skull consists of the calvaria which contains the brain, and the facial skeleton, also known as the viscerocranium.

The facial skeleton consists of the following bones:

  • Nasal bones
  • Lacrimal bones
  • Palatine bones
  • Zygomatic bones
  • Maxillae
  • Inferior nasal conchae
  • Vomer

The maxillae (plural) are paired bones which are located between the orbit and the upper teeth, forming the upper part of the jaw. The maxilla consists of four processes:

  1. Zygomatic process – sticks out laterally to articulate with zygomatic bone
  2. Frontal process – projects superiorly and articulates with frontal bone
  3. Alveolar process – forms the tooth sockets for the upper teeth
  4. Palatine process – located inferiorly and forms the anterior portion of the hard palate

Learn more about the anatomy of the skull in this tutorial.

Pectineus

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Pectineus

Pectineus

The structure indicated is the pectineus muscle.

The pectineus muscle is one of six muscles in the medial compartment of the thigh. The thigh consists of three muscular compartments:

  1. Anterior
  2. Medial
  3. Posterior

The medial compartments consists of the following muscles:

  • Gracilis
  • Pectineus
  • Adductor longus
  • Adductor brevis
  • Adductor magnus
  • Obturator externus

All the muscles of the medial compartment are innervated by the obturator nerve except for the pectineus (femoral nerve) and the hamstring part of the adductor magnus (tibial division of sciatic). The muscles of the medial compartment generally serve to adduct the thigh at the hip joint. Due to the innervation of the pectineus muscle by the femoral nerve, it is sometimes classified as a muscle of the anterior compartment of the thigh.

Origin: Pectineal line of pubic bone

Insertion: Upper medial haft of femur

Action: Adducts hip and flexes hip

Innervation: Femoral nerve

Learn more about the anatomy of the thigh muscles in this tutorial.

Vastus Lateralis

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Vastus Lateralis

Vastus Lateralis

The structure indicated is the vastus lateralis

The vastus lateralis is one of the muscles that makes up the quadriceps femoris, and is contained in the anterior compartment of the thigh. The muscles of the anterior compartment are all innervated by the femoral nerve and serve generally to extend the leg at the knee joint.

The four muscles that make up the quadriceps femoris are the:

  • Rectus femoris
  • Vastus lateralis
  • Vastus medialis
  • Vastus intermedius

In addition to the quadriceps muscles, the Sartorius muscle is also located in the anterior compartment together with the distal ends of the iliopsoas muscles.

Origin: Superior half of anterior and lateral surfaces of femur

Insertion: lateral border of base of patella (then joins patella ligament to attach to tibial tuberosity)

Action: Extends the knee

Innervation: Femoral nerve

Learn more about the anatomy of the anterior muscles of the thigh in this tutorial.

Foramen Lacerum

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Foramen Lacerum

Foramen Lacerum
Foramen Lacerum

The structure indicated is the foramen lacerum.

The floor of the cranial cavity consists of three cranial fossae:

  1. Anterior cranial fossa
  2. Middle cranial fossa
  3. Posterior cranial fossa

There are several holes in the floor of the cranial cavity which allow structures to enter and exit the skull, known as foramen. Foramen (foramina is plural), are holes in the human body which allow other structures to pass through. In the case of the skull, foramina permit the passage of arteries, veins and nerves.

The middle cranial fossa consists of the following foramina:

  • Superior orbital fissure
  • Foramen rotundum
  • Foramen ovale
  • Foramen spinosum
  • Foramen lacerum

The foramen lacerum lies beneath the carotid canal and in adult life is closed off by cartilage.

Learn more about the anatomy of the formina of the skull in this tutorial.

Piriformis

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Piriformis

Piriformis

The structure indicated is the piriformis muscle.

The piriformis muscle is one of the muscles of the gluteal region. The muscles in the gluteal region are divided into a superficial and deep group. There are four muscles of the superficial group:

  1. Gluteus maximus
  2. Gluteus medius
  3. Gluteus minimus
  4. Tensor fasciae latae

There are 5 muscles in the deep group:

  1. Gemellus superior
  2. Gemellus inferior
  3. Quadratus femoris
  4. Piriformis
  5. Obturator internus

The deep muscles of the gluteal region generally serve to laterally rotate the femur.

The piriformis muscle passes through the greater sciatic foramen and divides it into two spaces:

  • Greater sciatic foramen above the piriformis (suprapiriform foramen)
  • Greater sciatic foramen below the piriformis (infrapiriform foramen)

Origin: Anterior portion of lateral process of sacrum. Gluteal surface of ilium at border of greater sciatic notch

Insertion: Superior border of greater trochanter

Action: Lateral rotation of hip. Assists abduction of hip when hip is flexed.

Innervation: Nerve to piriformis

Learn more about the anatomy of the gluteal muscles in this tutorial.

Vastus Lateralis

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Vastus Lateralis

Vastus Lateralis

The structure indicated is the vastus lateralis

The vastus lateralis is one of the muscles that makes up the quadriceps femoris, and is contained in the anterior compartment of the thigh. The muscles of the anterior compartment are all innervated by the femoral nerve and serve generally to extend the leg at the knee joint.

The four muscles that make up the quadriceps femoris are the:

  • Rectus femoris
  • Vastus lateralis
  • Vastus medialis
  • Vastus intermedius

In addition to the quadriceps muscles, the Sartorius muscle is also located in the anterior compartment together with the distal ends of the iliopsoas muscles.

Origin: Superior half of anterior and lateral surfaces of femur

Insertion: lateral border of base of patella (then joins patella ligament to attach to tibial tuberosity)

Action: Extends the knee

Innervation: Femoral nerve

Learn more about the anatomy of the muscles of the thigh in this tutorial.


Episode 2 – Skeletal Muscle Structures

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Learn all about the structures that make up skeletal muscle in this brand new physiology tutorial.

Episode 3 – Neuromuscular Junction

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Learn all about the neuromuscular junction in this brand new physiology tutorial.

Cribriform Plate

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Cribriform Plate

Cribriform Plate

The structure indicated is the cribriform plate.

The cribriform plate of the ethmoid bone sits lateral to the crista galli and has numerous foramen which permit the passage of the olfactory nerves which pass from the nasal mucosa to the olfactory bulb.

Learn more about the bones of the skull in this tutorial.

Extensor Carpi Radialis Brevis

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Extensor Carpi Radialis Brevis

Extensor Carpi Radialis Brevis

The structure indicated is the extensor carpi radialis brevis muscle of the forearm.

The extensor carpi radialis brevis muscle is one of 7 muscles located in the superficial compartment of the posterior forearm. The posterior forearm consists of a superficial and a deep compartment. The superficial compartment contains 7 muscles, whereas the deep compartment contains 5 muscles.

The superficial compartment of the posterior forearm includes the following 7 muscles:

  1. Brachioradialis
  2. Extensor carpi radialis longus
  3. Extensor carpi radialis brevis
  4. Extensor digitorum
  5. Extensor digiti minimi
  6. Extensor carpi ulnaris
  7. Anconeus

The extensor carpi radialis brevis muscle serves to abduct and extend the wrist joint. The muscles of the posterior compartment of the forearm originate from the lateral epicondyle of the humerus and the supraepicondylar ridge and they are all innervated by the radial nerve, they generally extend the wrist joint.

Origin: lateral epicondyle of humerus

Insertion: base of 3rd metacarpal

Action: Extends and abducts wrist

Innervation: Radial nerve

Learn more about the muscles of the forearm in this tutorial.

Foramen Spinosum

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Foramen Spinosum

Foramen Spinosum
Foramen Spinosum

The structure indicated is the foramen spinosum.

The floor of the cranial cavity consists of three cranial fossae:

  1. Anterior cranial fossa
  2. Middle cranial fossa
  3. Posterior cranial fossa

There are several holes in the floor of the cranial cavity which allow structures to enter and exit the skull, known as foramen. Foramen (foramina is plural), are holes in the human body which allow other structures to pass through. In the case of the skull, foramina permit the passage of arteries, veins and nerves.

The middle cranial fossa consists of the following foramina:

  • Superior orbital fissure
  • Foramen rotundum
  • Foramen ovale
  • Foramen spinosum
  • Foramen lacerum

The foramen spinosum is found in the greater wing of the sphenoid bone. There are two foramina in the sphenoid bone:

  1. Foramen spinosum
  2. Foramen ovale

The following structures pass through the foramen spinosum:

  • Middle meningeal artery
  • Middle meningeal vein
  • Meningeal branch of the mandibular vein

Learn more about the foramina of the skull in this anatomy tutorial

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