Innervation of the Hand: Ulnar, Median and Radial Nerve Anatomy

Innervation of the Hand: Ulnar, Median and Radial Nerve Anatomy

pediagenosis    August 23, 2026   

INNERVATION OF THE HAND

Nerve branches from the ulnar, median, and radial nerve supply motor, sensory, and autonomic vasomotor function in the hand.

ULNAR NERVE

The ulnar nerve (C[7], 8; T1) is the main continuation of the medial cord of the brachial plexus. In the forearm and hand, the ulnar nerve gives off articular, muscular, palmar, dorsal, superficial and deep terminal, and vascular branches. It divides into branches for the areas of skin on the medial side of the back of the hand and fingers (see Plate 4-12). The ulnar nerve enters the hand to the radial side of the pisiform between the palmar carpal ligament and the flexor retinaculum. Just distal to the pisiform, the ulnar nerve divides into superficial and deep branches.

Pressures and Volumes During Normal Breathing: FRC, Intrapleural Pressure and Lung Volumes

Pressures and Volumes During Normal Breathing: FRC, Intrapleural Pressure and Lung Volumes

pediagenosis    August 23, 2026   

Pressures And Volumes During Normal Breathing

Functional residual capacity

The volume left in the lungs at the end of a normal breath is known as the functional residual capacity (FRC). At FRC, the respiratory muscles are relaxed and its volume is determined by the elastic properties of the lungs and chest wall.

The lungs are elastic bodies whose resting volume when removed from the body is very small. The natural resting position of the chest wall, seen when the chest is opened surgically, is about 1 L larger than at the end of a normal breath.

Meckel Diverticulum: Symptoms, Complications, Diagnosis, and Treatment

Meckel Diverticulum: Symptoms, Complications, Diagnosis, and Treatment

pediagenosis    August 22, 2026    Comment   

VARIANTS OF VITELLINE DUCT REMNANTS

Meckel Diverticulum

The vitelline, or omphalomesenteric, duct connects the yolk sac with the primitive tubular gut in the early embryonic stages and normally involutes at about the 7th week of fetal life, leaving no trace of its existence. Failure of the vitelline duct to disappear in its entire extension results in a variety of remnants, which include a diverticulum (Meckel diverticulum) attached to the ileum, omphalomesenteric cysts (enterocysts), omphalomesenteric fistulae that drain through the umbilicus, and fibrous bands from the diverticulum to the umbilicus that predispose to bowel obstruction. The most common form is Meckel diverticulum.

Atrial Septal Defect (ASD): Types, Symptoms, Diagnosis and Treatment

Atrial Septal Defect (ASD): Types, Symptoms, Diagnosis and Treatment

pediagenosis    August 20, 2026    Comment   

ATRIAL SEPTAL DEFECTS

DEFECTS OF THE ATRIAL SEPTUM

The atrial septum normally consists of two overlapping, closely adjacent components. Each forms an incomplete partition. The right-side component, corresponding to the embryonic septum secundum, is muscular and firm and has a posteroinferior oval-shaped opening, the foramen ovale. The left-side component, derived from the embryonic septum primum, is fibrous and thin and has a somewhat round opening anterosuperiorly, the ostium secundum. Together, the two components act as a one-way flap valve, allowing the flow of blood from right to left (normal before birth) but not from left to right. After birth, with the establishment of pulmonary circulation, the increased amount of blood entering the left atrium elevates the pressure in that chamber, thereby closing the flap valve. In most cases, this functional closure is eventually followed by anatomic closure; that is, the two components of the septum fuse. In the minority of cases where fusion fails, an increase in the right atrial pressure due to congenital cardiac anomalies, or any other condition that elevates right ventricular and right atrial pressure, causes the right atrial blood to flow again into the left atrium. Such a probe-patent foramen ovale, however, should not be considered a form of atrial septal defect; it causes no hemodynamic abnormalities by itself. In ASD there is an abnormal opening in the atrial septum allowing blood to flow either way; a predominantly left-to-right shunt usually exists. With associated anomalies or other conditions tending to increase right atrial pressure, the shunt is always from right to left, as in tricuspid valve atresia, or an initially left-to-right shunt reverses, as occurs after pulmonary vascular changes with pulmonary hypertension.

Lymphatic Drainage of Internal Genitalia: Uterus, Ovary, Tube, Cervix & Vagina

Lymphatic Drainage of Internal Genitalia: Uterus, Ovary, Tube, Cervix & Vagina

pediagenosis    August 18, 2026    Comment   

LYMPHATIC DRAINAGE II—INTERNAL GENITALIA

The lymphatics of the uterus are contained within three main networks or plexuses one at the base of the endometrium, another in the myometrium, and a third subperitoneally. No lymphatics, surprisingly, have been detected in the superficial parts of the endometrium. The principal collecting trunks pass outward at the isthmus along the course of the uterine vessels. Drainage from the uterine body and from the cervix is similar, except that, in the region of the fundus, lymphatics are more likely to pass directly along with the ovarian lymphatics to the periaortic nodes. Occasionally, also, lymphatics may extend along the inguinal ligament to the femoral nodes. The number of lymph nodes in the group of parauterine nodes is small; most frequently there is a single node immediately lateral to each side of the cervix and adjacent to the pelvic course of the ureter. Although anatomists frequently do not comment about the parauterine nodes, the group receives special attention in radical surgical operations to treat uterine or cervical malignancy. Primary drainage to this node originates in the vagina, cervix, and uterus. Secondary drainage from this node is to the internal iliac nodes on the same side of the pelvis.

Lymphatic Drainage of the External Genitalia: Inguinal Nodes & Cloquet Node

Lymphatic Drainage of the External Genitalia: Inguinal Nodes & Cloquet Node

pediagenosis    August 17, 2026   

LYMPHATIC DRAINAGE—EXTERNAL GENITALIA

A network of lymphatic anastomoses drains the external genitalia, the lower third of the vagina, and the perineum. Bilateral or crossed extension and drainage is common. The superficial femoral nodes are reached through the superficial external pudendal lymphatic vessels, although the superficial external epigastrics may also play a role. From the region of the clitoris, deeper lymphatic vessels may pass direct to the deep femoral nodes, particularly to Cloquet node in the femoral canal, or through the inguinal canal to the external iliac nodes. Cloquet node is thought to be the sentinel node between the superficial and deep inguinal/obturator lymph nodes. Sometimes, intercalated nodes may be encountered in the prepubic area or at the external inguinal ring. The lowermost portion of the vagina, like the vulva, may drain to the femoral nodes. This complex network of lymph nodes is clinically important, for these are the nodes to which cutaneous and vulvovaginal gland malignancies may drain. Regional lymph node dissections are routinely performed in the surgical treatment of vulvar cancer as the status of regional lymph nodes is essential for therapeutic planning and overall prognosis. Superficial nodes in the groin may also become enlarged when significant inflammation is present in vulvar structures (e.g., Bartholin gland infections).

Nevus Lipomatosus Superficialis: Symptoms, Causes, Histology & Treatment

Nevus Lipomatosus Superficialis: Symptoms, Causes, Histology & Treatment

pediagenosis    August 17, 2026    Comment   

Nevus Lipomatosus Superficialis

Nevus lipomatosus superficialis is a not-uncommon benign skin growth that is considered to be a hamartomatous proliferation of adipose tissue located in the dermis. It was originally named nevus lipomatosus cutaneous superficialis of Hoffman-Zurhelle. There are no known systemic associations with this benign skin growth, and no inheritance pattern has been described.

Innervation of Genitalia and Perineum: Nerves, Scrotal Pain & Bulbospongiosus Reflex

Innervation of Genitalia and Perineum: Nerves, Scrotal Pain & Bulbospongiosus Reflex

pediagenosis    August 17, 2026   

Innervation of Genitalia II and of Perineum

The nerves supplying the anterior scrotal wall are the ilioinguinal and the external spermatic branch of the genitofemoral branch of the lumbar nerves. The superficial perineal branches of the internal pudendal nerve, along with branches from the posterior cutaneous nerves of the thigh, innervate the posterior scrotal wall. The unstriated muscle in the dartos fascia is innervated by fine autonomic fibers that arise from the hypogastric plexus and reach the scrotum along with the blood vessels. Because of this complex innervation from various sources, the entire scrotum is difficult to anesthetize with local anesthesia, unlike the spermatic cord and testicles.

Connective Tissue: Types, Functions, Cells, and Extracellular Matrix

Connective Tissue: Types, Functions, Cells, and Extracellular Matrix

pediagenosis    August 16, 2026   

Connective or Supportive Tissue.

Connective or supportive tissue is the most abundant tissue in the body. As its name suggests, it connects and binds or supports the various tissues. Connective tissue is unique in that its cells produce the extracellular matrix that supports and holds tissues together. The capsules that surround organs of the body are composed of connective tissue. Bone, adipose tissue, and cartilage are specialized types of connective tissue that function to support the soft tissues of the body and store fat. The proximity of the extracellular matrix to blood vessels allows it to function as an exchange medium through which nutrients and metabolic wastes pass.

Sporotrichosis: Causes, Symptoms, Diagnosis, Histology and Treatment

Sporotrichosis: Causes, Symptoms, Diagnosis, Histology and Treatment

pediagenosis    August 16, 2026    Comment   

Plate 6-24

SPOROTRICHOSIS

Sporothrix schenckii is an environmental fungus that is capable of causing human disease after direct inoculation into the skin. Inoculation is the cause of cutaneous sporotrichosis, which is considered to be a subcutaneous mycosis. Unusual cases of inhalation sporotrichosis have been described in the literature, as have cases of central nervous system disease. These cases occur almost exclusively in immunosuppressed hosts. Sporotrichosis has classically been associated with inoculation after the prick from a rose plant. This is well reported; the fungus can be isolated from rose plants but is also found on many other plants and in soil environments.