Human Anatomy and Physiology Overview
Muscle
Muscle is a structure formed by a group of fibers composed of muscle cells containing actin and myosin.
- Fiber smooth: Involuntary muscle contraction.
- Fiber striated: Voluntary contraction.
According to their flattened fusiform shape, muscles can be long or short. A muscle is composed of a tendon and other tendon fibers. Its function is to stabilize and move the levers that make bone joints.
Bone
Bone is a highly vascularized structure. The fundamental unit of bone is the osteon. There is a channel called the Haversian Canal, which contains a venule, arteriole, and nerve. Cells called osteoblasts form around the Haversian Canal, creating the interstitial substance that forms the bone. As we age, bones become harder but more brittle, losing elasticity.
In long bones, we identify two extremities:
- Proximal epiphysis: Closest to the shaft.
- Distal epiphysis: Farthest from the shaft.
The epiphyses are covered with cartilage. Below the cartilage, we find compact bone consisting of cancellous bone. The two epiphyses are united by the spinal canal, formed by bone marrow. Vitamin D is crucial for bone growth. There are also short bones with spongy tissue.
Waist-Pelvis
The pelvis has two circles: the greater pelvis and the lesser pelvis. The innominate bone is formed by three parts: the ischium, ilium, and pubis.
- External surface: Also called the external iliac pit.
- Internal surface: The internal iliac fossa.
- Cost hiliaca: The upper edge.
There are two slopes: an anterior and a posterior. The pelvic bone begins at the leading edge and continues with the obturator foramen. The hamstring is a C-shaped bone that is continuous with the pubis. Vessels and nerves pass through the obturator foramen. The inner side supports the pelvic organs and the Iliana muscle, which is inserted into the iliac fossa and moves down to integrate with the femur.
The muscles of the buttocks include:
- Gluteus maximus: Inserted into the internal iliac pit.
- Gluteus medius: Inserted into the internal iliac pit and the femur.
- Gluteus minimus: Inserted similarly to the gluteus medius but on the other side of the femur. Important for hip stability.
Femur
The femur is a long bone with a distal and a proximal epiphysis.
- Proximal femoral head: Bound by a sort of trunk bone connecting it with the body of the femur, called the femoral neck.
- Greater trochanter: A large boulder continuous with the shaft.
- Lesser trochanter: Opposite the greater trochanter.
The femur is continuous with the bone marrow to consist of the lower extremity. The patella articulates with the distal epiphysis.
Clavicle
The clavicle is a long bone with a lazy S-shape. The inner curve has a concavity oriented toward the chest, while the outer curve is upside down and harder to feel. It has two extremities:
- External extremity: More bulky.
- Acromial extremity: Flattened.
Shoulder Girdle
The shoulder girdle is the meeting point of the proximal upper limb, extending from the base of the neck to the 4th or 5th rib. It provides skeletal bonding between the trunk and the upper limb. It consists of 2 blades, 2 clavicles, the chest, and 2 humeri. The shoulder girdle has four joints:
- Scapulohumeral joint: The most mobile joint, allowing adduction, abduction, flexion, extension, rotation, circumduction, and internal and external movements. It has articular surfaces for the humerus and scapula. The head of the humerus is located in the flue, and the scapula is in the glenoid. The media union of art consists of the capsule, ligaments of reinforcement, and the synovial membrane.
- Sternoclavicular joint: Constituted by the internal extremity of the clavicle and the manubrium. It belongs to the genre of art.de saddle, although sharing an artrodia. The joining means is a capsule, 4 ligaments, and synovium. Its movements are for lifting, retroposition, and decline of the clavicle.
- Acromioclavicular joint: Formed by the end of the clavicle and the inner edge of the acromion. Presents an interarticular fibrocartilage or meniscus. The joining means is a capsule, 2 ligaments, synovial coracoclavicular ligaments. Its movement is sliding.
- Scapulothoracic joint: Not a true joint. Allows the scapula to slide over the rib cage. It consists of two spaces (scapular and serratus anterior). The scapula has gliding movements in all directions.
Muscles of the Shoulder and Upper Limb
Deltoid
The deltoid muscle covers the shoulder. It has multiple attachments, but three are important: the anterior border of the clavicle, the outer edge of the acromion, and the scapular spine. It extends to the humerus and is the flexor, abductor, and extensor of the scapulohumeral joint.
Supraspinatus
The supraspinatus muscle stays in the supraspinous fossa of the scapula and ends in a tendon that inserts into the greater tuberosity. It is a deltoid auxiliary, helping in arm abduction.
Infraspinatus
The infraspinatus muscle goes from the infraspinous fossa to the greater tuberosity. It is an external rotator, and its innervation comes from the brachial plexus.
Teres Minor
The teres minor muscle runs from the axillary border of the scapula to the greater tuberosity.
Teres Major
The teres major muscle runs from the inferior angle of the scapula to the bicipital groove. It is a shoulder internal rotator and adductor. It unites the humeral head and glenoid. Its nerve supply comes from the brachial plexus.
Arm Muscles
Biceps Brachii
The biceps brachii muscle consists of two muscular bodies, one from the coracoid process and the other from the outer corner of the scapula. The muscle ends in a tendon that inserts into the bicipital tuberosity of the radius. Its main function is to flex the elbow, but it is also a shoulder flexor and adductor. It is innervated by the musculocutaneous nerve.
Coracobrachialis
The coracobrachialis muscle is inserted into the coracoidal and anteromedial face of the humerus. It is a flexor and adductor of the arm and is innervated by the musculocutaneous nerve.
Brachialis
The brachialis muscle inserts proximally on the anterior faces of the humerus and distally at the base of the coracoid process of the ulna. It is an elbow flexor and is innervated by the musculocutaneous nerve.
Triceps Brachii
The triceps brachii muscle has a threefold origin: the long head, the vastus medialis, and the vastus lateralis. It is an extensor of the elbow and a shoulder adductor (long portion).
Elbow Joint
The elbow joint connects the humerus to the forearm bones (radius and ulna). It allows flexion-extension and pronosupination movements. It consists of three differentiated joints: radiohumeral, ulnohumeral, and proximal radioulnar.
Forearm Muscles
The forearm muscles are divided into three regions:
- Anterior region: Contains muscles involved in flexion and pronation.
- Posterior region: Contains muscles involved in extension and supination.
- Lateral region: Contains muscles involved in wrist extension and radial deviation.
Wrist and Hand
The wrist and hand consist of the distal radius, distal ulna, carpal bones, metacarpals, and phalanges. They form various joints, including the radiocarpal joint, intercarpal joints, carpometacarpal joints, metacarpophalangeal joints, and interphalangeal joints.
Intrinsic Muscles of the Hand
The intrinsic muscles of the hand are divided into three regions:
- Thenar region: For the thumb.
- Hypothenar region: For the little finger.
- Palmar region: Located between the thenar and hypothenar regions.
Knee and Leg
The knee joint consists of the patellofemoral and femorotibial articulations. It is a hinge joint that allows flexion and extension. The ligaments of reinforcement include the internal lateral ligament, lateral ligament, anterior cruciate ligament, and posterior cruciate ligament.
Leg Muscles
The leg muscles include the tibialis anterior, extensor hallucis longus, extensor digitorum longus, peroneus tertius, peroneus longus, peroneus brevis, gastrocnemius, soleus, plantaris, popliteus, flexor digitorum longus, tibialis posterior, and flexor hallucis longus.
Ankle and Foot
The ankle and foot consist of the distal tibia, distal fibula, tarsal bones, metatarsals, and phalanges. They form various joints, including the ankle joint, intertarsal joints, and tarsometatarsal joints.
Intrinsic Foot Muscles
The intrinsic foot muscles are divided into three regions:
- Internal plantar region: For the big toe.
- External plantar region: For the 5th toe.
- Medial plantar region: For the middle toes.
Iliopsoas
The iliopsoas muscle is located in the abdominal cavity and anterior thigh. It consists of two parts: the psoas major and iliacus. It is a hip flexor and is innervated by branches of the lumbar plexus and femoral nerve.