Pelvis and Perineum

The Pelvic girdle

The pelvic girdle is the collection of ring shaped bones that connect the vertebral column to the right and left femurs.  They function to bear the weight of the upper body, transfer weight from the axial to the appendicular skeleton, and attachment for the muscles of movement in the lower body.  The pelvic girdle consists of three bones:  right and left hip bones and the sacrum.  Five fused bones come together to form the sacrum.  In infancy and childhood the hip bones are three individual bones: the ilium, ishium, and the pubis.  After puberty these bones fuse to form one hip bone.  The hip bones are connected by what is known as the pubic symphysis.  There are two primary joints of the pelvic girdle. These joints are the sacroiliac joints and the pubic symphysis.

Pelvic Fractures

Pelvic fractures often occur in the weak spots in the pelvis.  They are often the result of direct trauma such as an automobile accident or direct force to the pelvis due to a fall.  The weak spots of the pelvis are the pubic rami, the acetabula, sacroiliac joints, and the alae of the ilium. Other side effects of a pubic fracture are injured soft tissue, nerves and organs.  When the pubo-obturator area is injured, the fracture then becomes complicated, because this area has a close relationship with the urinary bladder and urethra. Pelvic fractures can also cause the urinary bladder or the urethra to tear. 

Urinary Organs

Wastes from the kidneys must be excreted from the body by way of the urinary organs.  The ureters are the muscular tubes that move urine from the kidneys to the urinary bladder.  Ureters are about 25-30 cm in length and are thick muscular tubes.  They are considered retroperitoneal just like the kidneys.  The urinary bladder is the organ that stores urine for excretion. It is a hollow organ with strong muscular walls.  There are some subtle differences in the characteristics of the female urethra and the male urethra. The male urethra is 18-22 cm long, and it serves as an accessory organ to the reproductive system.  The male urethra is where the sperm exits the body.  There are four portions of the male urethra: preprostatic part, prostatic urethra, intermediate part, and the spongy urethra.  The female urethra is about 4 cm in length and is not apart of the reproductive system in females. 

Rupture and Hernia of the Urinary bladder
Oftentimes during childbirth women lose the support of the urinary bladder because of damage to the pelvic floor.  The perineal muscles could be lacerated, a lesion could be present on the nerves that innervate the bladder, or the fascia that supports the bladder could rupture.  Pelvic fractures can cause the bladder to rupture.  When the bladder ruptures, it is often followed by a torn peritoneum.  With a ruptured bladder urine is allowed to excape extraperitoneally and intraperitoneally.

Anal Canal
The anal canal is where the large intestine terminates and becomes the external opening for the release of wastes.  This canal ends at the anus.  The anal canal is surrounded by two sphincters that are between the anococcygeal ligaments and the perineal body.  These sphincters must relax before wastes can exit the body.  The internal anal sphincter is the involuntary sphincter of the two anal canal sphincters and surrounds the upper two-thirds of the anal canal.  It prevents leakage or flatulence, so it is contracted most of the time.  It relaxes in response to fecal material or gas.  The external anal sphincter is the voluntary sphrincter of the anal canal.  It forms the inferior one-third of the anal canal.  This sphincter blends with the puborectalis muscle. 

Hemorrhoids

Internal hemorroids are the entering of  rectal mucosa into the anal canal.  Because the anal sphincters are contracting, the blood flow to this mucosa is hindered.  This causes the ulceration and strangulation.  The arterial anastomoses in this area generate bright red bleeding. Internal hemorrhoids are typically not painful, because this area is innervated by visceral afferent pain fibers. Blood clots in the veins of the external rectal venous plexus is what causes the formation of external hemorrhoids.  Pregnancy, chronic constipation, and straining on the toilet seat are some of the predisposing factors for external hemorrhoids.  The area where external hemorrhoids form is innervated by somatic sensory fibers and often causes pain. 

Abdominopelvic Region Blog #4

Stomach
The stomach is an organ designed for storage of ingested food.  This organ has the ability to expand to hold up to 2-3 L of food. There is mechanical and chemical digestion occurring in the stomach. The primary function of the stomach is enzymatic digestion.  Gastric juice is the chemical that converts food into chyme to enter the duodenum.  The stomach consists of two curvatures, the lesser curvature and the greater curvature.   The arterial supply to the stomach comes from celiac trunk. 

Ulcers of the stomach
Most ulcers formed in the stomach are caused by a bacterium, Helicobacter Pylori. The bacteria disrupts the mucous layer of the stomach, which exposes the stomach to the effects of gastric juice and pepsin.  Erosion of the gastric arteries withing the stomach can cause bleeding.  Acid is secreted by the parietal cells of the stomach and that is controlled primarily by the vagus.  Sometimes, a vagotomy can be performed on individuals with recurring ulcers.

Spermatic Cord
The spermatic cord is what suspends the testes in the scrotum.  It begins at the deep inguinal ring lateral to the inferior epigastric vessels and exits the superficial inguinal ring.  There are three fascias that cover the spermatic cord. They are the internal spermatic fascia, cremasteric fascia, and external spermatic fascia.  Within the cremasteric fascia, there are loops of the cremaster muscle.  When the testes are exposed to cold temperatures, the cremaster muscle draws the testes superiorly in the scrotum. In warm temperatures, the testes descend to the deep portions of the scrotum.  Spermatogenesis occurs in the testes, and this reflexive response by the cremaster muscle is an attempt to regulate the environment of the testes.  The spermatic cord contains the ductus deferens, testicular artery, artery of the ductus deferens, and vestige of processus vaginalis. 

Inguinal Hernias
Inguinal hernias account for 75% of abdominal hernias.  An inguinal hernia is defined as, "a protrusion of parietal peritoneum and viscera, such as the small intestine, through a normal or abnormal opening from the cavity in which they belong." (Moore 212)  Most hernias are indirect hernias. In order to palpitate an inguinal hernia, the palmer surface of the middle finger is placed over the inquinal triangle and the person is asked to cough or bear down.  A direct hernia will yield a sudden impulse when the person coughs or bears down. 



Spleen
The spleen is found in the left upper quadrant of the abdomen.  The inferior thoracic cage is what protects the spleen.  During embryonic development the spleen is involved in the formation of blood, however after birth the spleen is involved in the identifying, removing and destroying red blood cells.  The spleen is often known as the reservoir for red blood cells.  This organ is not considered a vital organ, which means that life can be sustained without this organ.  The spleen is usually 12 cm long and about 7 cm wide.  Blood is supplied to the spleen by the splenic artery, and the spleen is drained by the splenic vein. 

Splenectomy from ruptured spleen
Oftentimes, the spleen is removed when it ruptures to prevent the person from bleeding to death.  The spleen is the most frequently injured organ in the abdomen.  When the ribs are fractured, it makes the spleen vulnurable to damage.  A total splenectomy can make a person more suceptible to some bacterial infections.  If part of the spleen is removed it is often followed by regeneration. 

Anterior Thorax

Pleura of the lungs
The pleural sac consists of 2 membranes that enclose the lungs.  The visceral pleura adheres to the surface of the lung itself and the parietal pleura lines the pulmonary cavity. The visceral pleura cannot be removed from the lung during a cadaveric dissection.  The parietal pleura is thicker than the visceral pleura and consists of three distinct parts.  Three parts of the parietal pleura are the costal part, the mediastinal part, and diaphragmatic part.  The pleural cavity is the space between the visceral pleura and the parietal pleura.  The pleural cavity consists of a capillary layer of serous pleural fluid that allows smooth movement during respiration.  This fluid also keeps the lungs adhered to the surface of the thoracic cavity. 

Pleurisy
Pleurisy is the inflammation of the lining of the lungs. The distinguishing characteristic of pleurisy is the sound of friction in the lungs with a stethoscope. The sound can be described as something similar to a "hair clump being rolled between the fingers."  Patients with pleurisy often describe the condition as a stabbing, sharp pain during respiration.  Pains often become more intense with physical exertion such as climbing stairs.

Nerves of the Lungs and Pleurae
The lungs and visceral pleura are innervated by the pulmonary plexus.  These nerves contain parasympathetic, sympathetic, and visceral afferent fibers.  The parasympathetic fibers are derived from presynaptic fibers of the vagus nerve.  These fibers provide motor innervation to the smooth muscle, inhibitory action to the pulmonary vessels, and secretory to the glands of the lungs.  The sympathetic fibers are postsynaptic neurons.  They function in opposition to the parasympathetic fibers and this includes inhibitory to the brochial muscle, motor to the pulmonary vessels, and inhibitory to the glands of  the bronchial tree.  The visceral innervation to the lungs is characterized as being either reflexive or nociceptive.  The reflexive fibers accompany the parasympathetic fibers of the bronchial tree.  The nociceptive fibers accompany the sympathetic fibers of the bronchial tree.  The parietal pleura innervation is provided by the intercostal nerves and the phrenic nerves.

Pleural Pain
The visceral pleura receives no innervation by nociceptors, so no pain sensation is felt in this pleura.  However, the parietal pleura is extremely sensitive to pain because of the numerous intercostal nerves and phrenic nerves that innervate this region.  The pain sensation felt in the parietal pleura is labeled referred pain.  Irritation to the diaphragmatic regions of the parietal pleura produce referred pain in the thoracic and abdominal walls.  The referred pain sends signals to the dermatones in different areas that produce pain in a specified area of the body as shown in the figure below. 


The Pericardium
The pericardium is housed within the middle mediastinum along with the heart and the root of its great vessels.  The pericardium is a two layer closed sac.  The toughest layer is the fibrous pericardium, and it is continuous with the central tendon of the diaphragm.  The serous pericardium is mostly mesothelium.  The mesothelium around the heart is composed of a thin layer of flat cells that line the internal surface of the fibrous pericardium and the external surface of the heart.  The arterial supply to the pericardium is the pericardiacophrenic artery.  This artery branches off of the internal thoracic artery.  The venous blood drainage of the pericardium is the pericardiacophrenic veins and they branch off of the brachiocephalic veins. Nerve innervation for the pericardium is the phrenic nerve (C3-C5).

Pericardiocentesis
In order to remove excess fluid that has accumulated around the heart, medical professionals often perform a pericardiocentesis.  This consist of inserting a bore needle in to the 5th or 6th intercostal near the sternum.  The cardiac notch in the left lung and the shallower notch in the left pleural sac is partially exposed to allow the need to pierce the pericardium to relieve excess fluid.  There is an alternate route to perform a pericardiocentesis by going toward the infrasternal angle.  This process requires more precision due to the fact that the lungs and the pleura must be avoided and the internal thoracic artery is easily punctured in this area. The figure below is presenting the alternate method for performing a pericardiocentesis by going toward the infrasternal angle. 

Upper Extremity

Brachial Plexus

The brachial plexus supplies nerve innervation to most of the upper limb.  The roots of the brachial plexus start at C5 and runs through T1.  They pass through the anterior and middle scalene muscles with the subclavian artery.  There are three trunks within the brachial plexus: superior, middle and inferior.  Each trunk emerges into an anterior and posterior division.  All the posterior divisions merge to form the posterior cord.  The anterior divisions of the superior trunk and the middle trunk meet to form the lateral cord and the anterior division of the inferior trunk merge to make the medial cord.  The figure below shows the organization of the brachial plexus from the roots to the cords. 

A neuronal disease associated with the brachial plexus is "acute brachial plexus neuritis".  This disease has no known cause.  Symptoms of brachial plexus neuropathy(BPN) include severe pain around the shoulder that start at night.  This condition typically is followed by weakness in the muscles and sometimes muscle atrophy.  BPN often follows some type of event like upper respiratory infection, vaccination, or non specific trauma.

Axillary Artery

The borders of the axillary artery are the lateral bordero of the first rib and the inferior border of the teres major.  As it passes the pectoralis minor it becomes the brachial artery.  The axillary artery is divided into three parts.  The first part of the axillary artery only has one branch and that is the superior thoracic artery.  The borders of the first part of the artery are the lateral border of the first rib and the medial border of the pectoralis minor.  The second part of the artery has two branches, and those are the thoracoacromial trunk and the Lateral thoracic artery.  The third part of the axillary artery consists of three branches which are the Subscapular artery, Anterior humeral circumflex artery, and the Posterior humeral circumflex artery.  The subscapular artery has two artery branching off of it, and they are the circumflex scapular artery and the thoracodorsal artery. The figure below is a representation of the axillary artery transcending into the brachial artery as it passes the pectoralis minor.


The axillary artery can be palpated on the most inferior part of the axilla. The third part of the axillary artery can be compressed against the humerus as a necessary result of some type of trauma.  If compression is required that is more proximal, the origin can be compressed as the subclavian artery crosses the first rib.  The first part of the axillary artery can enlarge and can result in an axillary artery aneurysm.  An axillary artery aneurysm will compress the trunks of the brachial plexus, and this will cause pain and loss of sensation on certain areas of the skin that the nerves of the brachial plexus innervate.  Aneurysms occur frequently in baseball pitchers because of the rapid movement of the arm.

The acromioclavicular joint is a plane type of synovial joint.  This joint allows the acromion of the scapula to articulate with the acromion of the clavicle.  The joint capsule contains a fibrous layer that is lined with a synovial membrane.  The ligaments of the acromioclavicular joint consist of the acromioclavicular ligament, coracoclavicular ligament (as shown in figure below), conoid ligament and the trapezoid ligament.  Movements of the acromioclavicular joint consists of rotation of the acromion of the scapula on the acromion of the clavicle.  Blood is supplied to the AC joint by the thoracoacromial arteries and innervation sources are the lateral pectoral and axillary nerves.  Shown below are some of the attributes of the acromioclavicular joint. 


The acromioclavicular joint is a joint that can be easily injured if exposed to some type direct trauma.  Oftentimes, the cause of these forceful blows are sports like football, soccer, hockey  or even martial arts.  Dislocation of the acromioclavicular joint is very common due to a hard fall on the shoulder or outstretched upper limb.  A dislocation of the acromioclavicular joint is considered severe when the acromioclavicular ligament and the coracoclavicular ligament are torn . This is due to the separation of the shoulder from the clavicle and the weight of the upper limb falls. 

Advanced Human Anatomy Post #1

Characteristics of the Cervical Vertebrae
There are seven cervical vertebrae in the average human vertebral column.  These vertebrae are found below the cranium and above the thoracic vertebrae.  Cervical vertebrae are smaller than any of the other vertebrae, because they do not bear as much weight as other vertebrae. They have the greatest range of motion.  Vertebra C1(atlas) is the most superior vetebra of the cervical vertebrae. The lateral masses of  the atlas articulate with the cranium at the occipital condyles of the cranium.  C1 is unique in that it has no spinous process or body.  The atlas rotates on the superior articular facets of C2 (axis) .  The axis is the strongest of the cervical vertebrae, and contains a tooth like projection called the dens. The head rotates about the dens. 

Injuries to the axis are the most common of the cervical vertebrae.  A fracture at the pars interarticularis is called traumatic spondylolysis.  Traumatic spondylolysis is usually the result of "hyperextension of the head on the neck".  This should not be confused with whiplash injury, which is hyperextension of the head and neck.  Hyperextension of the head on the neck is the premise behind the execution of criminals by hanging. 

Curvatures of the Vertebral Column
The human adult vertebral column has four curvatures.  There are two kyphoses in the thoracic and the sacral region, and there are two lordoses in the cervical and lumbar region.  The sacral and thoracic kyphoses are considered the primary curvatures of the human adult vertebral column.   These curvatures develop during the fetal period of human development. These curvatures are kept throughout the lifetime of human. The secondary curvatures are the cervical and lumbar lordoses.  The secondary curvatures start to develop during the late fetal period, but they do not become apparent until infancy. 



Abnormal curvatures in the human vertebral column must be observed in anatomical position.  Excessive thoracic kyphosis is commonly known as hunchback or humpback. It is more commonly called Dowager's hump in older women as a result of osteoporosis, but it is also found in older men as well. The vertebrae erode and collapse causing a hump in the thoracic region and a loss in height.   Excessive throracic kyphosis is characterized by an excessive posterior curve in the thoracic region. 



Intervertebral disks are the cushions between the vertebral bodies.  They are classified as symphyses joints and allow movement between individual vertebrae.  IV discs act as shock absorbers for the vertebral column.  IV discs contain an anulus fibrosus and a nucleus pulposus.  The anulus fibrosus runs the outside of the IV disc and consists of fibrocartilage. The nucleus pulposus is considered the core of the IV disc. It contains mostly water and is held mostly accountable for the flexible nature of the IV disc.  It is avascular, meaning, that it receives nutrients by diffusion from the anulus fibrosus and the verterbral body. 

When there is a protrusion of the nucleus pulposus, it is often recognized as a hernia in the lower back.  Herniation of the nucleus pulposus causes pain in the lower back as well as in the lower limbs.  Although there are many causes of lower back pain, herniation of the nucleus pulposus is usually an asymptomatic finding.  Most nucleus pulposus herniations occur in the lumbar and lumbosacracal region.  This is due to the IV discs being the largest in this region and have the greatest amount of movement.