Berg Adder

The Berg adder (Bitis atropos) is a small venomous snake, with triangular head. It is found in isolated areas in the mountain regions of Zimbabwe and the Cedarberg in the southwestern Cape, South Africa. Although it is aggressive and strikes readily, its cytotoxic venom, in most of the cases, is not fatal, despite its painful bite.

Physical Description

The Berg adder is a short viper, of the subfamily Viperinae. The adult measures between 30 and 45 cm in length. The head is triangular but elongated, lacking horns. It has a dark 'arrowhead' mark on the crown. Its thick, stout body is covered with keeled scales, forming between 29 and 33 rows on the dorsal aspect. Most individuals are boldly patterned in grey and bluish black. The females bears approximately 15 young in autumn. It usually preys on lizards and skinks.

Below, the Bitis atropos lying in the sunshine.

 

Flexor Digitorum Profundus

The flexor digitorum profundus is a third-layer muscle of the forearm, which lies on its anterior aspect, along the ulnar side. With a flat and wide belly, it springs from the proximal half of the anterior ulnar surface and the interosseous membrane. Then it runs downwards, ending up in four strong tendons, which travel under the flexor retinaculum and through the carpal tunnel. These tendons are inserted into the base of the distal phalanges of all four fingers.

Action

The flexor digitorum profundus muscle flexes the distal phalanges of all fingers, except the thumb.

Innervation

It is supplied by the median and ulnar nerve (C6-C8-T1).

Blood Supply

The flexor digitorum profundus receives oxygenated blood from secondary branches of ulnar artery.

Below, the third layer muscles of forearm, which include the flexor pollicis longus and the flexor digitorum profundus.

 

Histology of Thyroid

The histology of thyroid gland is a description of the essential tissue that constitutes this endocrine organ. The thyroid is composed of a collection of millions of sac-like cavities of various sizes; these are called follicles. The inner walls of these follicles consists in turn of a single layer of glandular epithelial cells, which are normally cuboidal and columnar when they are very active, and flat when inactive.  The structure of the gland also includes connective tissue stroma, which is made up of collagenous and elastic fibers enmeshed in a network of tiny blood vessels and nerves.

The epithelial cells lining each follicle produce thyroglobulin, which is released into the lumen of the follicle. The biosynthesis of thyroid hormones takes place at the cell colloid interface; this is where thyroglobulin is hydrolized to release thyroid hormones: thyroxine and triiodothyronine. Aside from the follicular cells, there are light appearing cells, which are often found in clusters between the follicles; these are called C-cells, which derive from the neural crest and secrete calcitonin. In adults, these C-cells represent only 1% of all the thyroid cells.

The normal growth and development of the body and tissue depend on the normal functioning of the thyroid gland, which secretes two types of hormones: thyroxine (T4) and triiodothyronine (T3). Thyroxine is produced by iodination (addition of iodine atoms in organic compounds) of the amino acid tyrosine and the oxidative condensation of two diiodotyrosine molecules, with the splitting off of alanine. Triiodothyronine, on the other hand, is synthesized by the oxidative condensation of monoiodotyrosine and diiodotyrosine.

Deltoid Muscle

The deltoid muscle (musculus deltoideus) is thick and triangular, covering the shoulder-joint, with the base facing upwards and the apex downwards. It is made up of large muscle fibers which converge fan-wise at the apex on lateral aspect of arm.

The deltoid muscle arises from the lateral portion of clavicle and superior and lateral surface of acromium (scapula). Its converging fibers run downwards to be inserted into the deltoid tuberosity of humerus. A large subdeltoid, or subacromial, bursa is lodged between the inferior surface of the muscle and the greater tuberosity of humerus. A bursa is a fluid-filled sac which functions to reduce friction.

Action

This powerful triangular muscle abducts the arm to the horizontal level (it pulls it laterally, extending it outwardly). It also pulls the arm forwardly and pronates it slightly.

Innervation

The deltoid muscle is innervated by the axillary nerve, which originates from the brachial plexus posterior cord.

Blood supply

It receives oxygenated blood from the posterior circumflex humeral, acromiothoracic, and deep brachial artery.

Below, the deltoid and other muscles of arm

Plain Mountain Adder

The plain mountain adder (Bitis inornata) is a small-size venomous viper which inhabits the grassland and hills of the Sneeuberg, near Graaff-Reinet, South Africa. Although it is not aggressive, its bite requires urgent hospitalization because its cytotoxic venom can cause necrosis and blood clots.

Physical Description and Habit.

The adult of the plain mountain adder measures between 25 and 35 cm in length. Although it is relatively short, its body is thick, with about 30 mid-body scale rows. The dorsal side (back) is dull brown, with fainter dark blotches. Its belly is dirty cream, with blotches limited to the sides.

The Bitis inornata is not well known as its habitat is very confined. It is active during the early morning and evening, hiding among stones and grass tussocks to ambush passing lizards, especially skinks and sand lizards. The female bears between 7 and 9 young in the late Summer.

Below, the plain mountain adder busking on a log in the morning shunshine.

 

Thyroid

The thyroid is an endocrine gland which produces iodine-containing hormones. These hormones take part in the regulation of metabolism and production of energy. Essentially, this secretory organ is made up of follicular cells, which are its parenchymal cells that form follicles (small cavities or sacs). These are special epithelial cells which secrete two hormones: thyroxine (T4) and triidothyronine (T3). Thyroxine increases the metabolic rate (oxygen consumption) and regulates growth and development, while triidothyronine has also a varied effect on the body growth, body temperature and heart rate.

Anatomical Description

The thyroid gland consists of two lateral lobes, which are connected by a narrow isthmus of glandular tissue. Therefore, it sits over the trachea like a saddle, with one lobe on each lateral side and the isthmus in front, lying below the cricoid cartilage. Each lobe is pear-shaped, measuring between 2.5 and 4 cm in length, 1.5 and 2 cm in width, 1 and 1.5 cm in thickness. The gland weighs about 20 grams in a male adult and about 14 grams in a female.

The thyroid gland is supplied by the superior thyroid and the inferior thyroid artery, with the former arising from the external carotid artery and the latter from the thyrocervical trunk of the subclavian artery. It is drained by the superior, lateral, and inferior thyroid veins. Blood flow is ablut 5 mL per minute; however, in hyperthyroidism, it increases about a hundred-fold.

Below, schematic picture of thyroid gland

 

Gaboon Adder

The Gaboon adder (Bitis gabonica) is a venomous viper snake whose natural habitat is the forests of eastern Zimbabwe and northern Zululand, South Africa. Although it is docile and rarely bites, when it does bite, the patient must be treated urgently. In 70% of the few cases of envenomation, the victim died before arriving at the hospital. The venom of this African viper contains powerful cytotoxins which destroy the body tissues and red blood cells.

Description

The Gaboon adder is a thick and large snake which usually measures between 80 cm and 120 cm (1.20 m). It has a prominent triangular head, which is covered in small scales, with a pair of horn-like scales on the snout. The head is whitish grey, with a thin dark central line. Its body has a geometric pattern of dark and light brown as well as light grey and dull black. The female bears between 40 and 45 young in late Summer. It has a nocturnal activity, preying on mice, squirrels, and lizards.

Below, the Bitis gabonica lying in wait over dry leaves.

 

Triceps Brachii

The triceps brachii is a wide and long muscle which lies on the posterior side of humerus. It is made up of three portions: a long, a lateral, and a medial head. All three heads are hidden by the deltoid muscle at their site of origin.

The long head of the triceps brachii arises by a wide tendon from the infraglenoid tubercle of scapula, traveling downwards in the space between the teres minor and major muscle. The lateral head originates from the posterior surface of humerus above the spiral groove of radial nerve, and from the medial and lateral intermuscular septa. The medial head arises also from the posterior surface of humerus but below the spiral groove.

As they extend downwards, all three heads meet to form a strong spindle-shaped belly, which continues stretching downwards by a strong tendon, which is inserted into the olecranon, which is a bony projection or process on the proximal end of ulna.

Action

Contraction of all heads of triceps brachii straighten and extend the forearm backwards at the elbow-joint; contraction of the long head pulls the arm backwards and adducts it. It works along with the pectoral and deltoid muscle when we do pushups on the floor; and, together with the latissimus dorsi, it contracts to help us do pullups on a bar.

Innervation

The triceps brachii muscle is innervated by branches of the radial nerve (C6-C7).

Blood Supply

It receives oxygenated blood from branches arising from the deep brachial and recurrent interosseous artery.

Below, schematic drawing of triceps brachii muscle, and the position it occupies on arm.

 

Human Pancreas

The human pancreas is a large digestive and endocrine gland. It is located behind the stomach, on the posterior abdominal wall, on the level of the lower two thoracic vertebrae (T11-T12) and the first upper lumbar (L1). Its long axis lies almost transversely across the vertebral column. One third of this gland is to the right side, while the other two thirds lie to the left of the midplane, in the epigastric and left hypochondriac region.

The length of the pancreas ranges between 16 and 22 cm, while its maximum width varies between 6 and 9 cm in the region of the head. With a thickness of about 3 cm, it weighs about 80 grams in adults. This endocrine organ is composed of three parts arranged next to one another: the head (caput pancreatis), which lies to the right of the spinal column; the body (corpus pancreatis); and a tail (cauda pancreatis). Between the head and the body, there is a small narrow part: the neck.

The head of the pancreas is in contact with the duodenum, being hugged by it in the shape of a horseshoe. Inside this gland and along its longitudinal axis, there is a long conduit or tube; it is the pancreatic duct, which joins the common bile duct right before it enters the duodenum. All the pancreatic digestive juice enzymes are discharged into the duodenum through this duct. Posteriorly, the head of pancreas is in contact the the right renal vein, the renal artery, and the inferior vena cava; the anterior surface of its head, on the other hand, is covered by the parietal peritoneum.

Function

Histologically and physiologically, the pancreas is divided into two parts: the exocrine and endocrine pancreas. The exocrine part secretes important digestive enzymes, like lipase, trypsine, and chimotrypsine, which are released into the duodenum to break down the food we eat so they can be absorbed by the walls of intestine. The endocrine portion is composed by the islets of Langerhans, which produce important hormones whose main function is blood sugar regulation and metabolism.

Below, anterior view of pancreas, with its head in the 'elbow' of duodenum. The stomach, which lies in front, is missing.

Posterior aspect of the same organ. You can see the common bile duct joining the pancreatic duct.

 

Function of Insulin

The function of insulin is to regulate sugar levels in the bloodstream. Thus, it plays an important metabolic role, doing the opposite of glucagon. Whereas glucagon keeps up the amount of glucose (sugar) to avoid hypoglycemia, insulin lowers glucose levels when they have gone up above normal limits, which range between 70 and 110 mg/dL.

How does it do it. This hormone induces the hepatocytes (liver cells) to metabolize and convert the excess glucose into glycogen. A large molecule of glycogen is made up of several smaller glucose molecules that have been folded up, compressed, and stored as a first fuel reserve. However, if you keep eating carbohydrates (flour, sugar, fructose), insulin will keep activating hepatocytes, but this time the liver cell mitochondria will convert the excess glucose into molecules of triglyceride (fat), which will be stored in the adipose cells as a second fuel reserve of the body, and this is how someone becomes obese.

As you know, insulin is produced by the beta cells of the islets of Langerhans of pancreas. Then it is released into the pancreas blood capillaries, which empty into the pancreatic veins and, these, into the splenic and portal vein, carrying the insulin-containing blood into the liver.

Jameson's Mamba

The Jameson's mamba (Dendroaspis jamesoni) is a long, slender snake which inhabits the forests of Central Africa. Since the genus Dendroaspis belongs to the large family Elapidae, its venom contains neurotoxins. Its bite can cause extended local swelling and respiratory paralysis. The diaphragm and the ribs intercostal muscles cannot be innervated and, therefore, cannot be expanded for inspiration, because the venom interferes with nerve cells impulses. Its venom is also cardiotoxic, causing arrhytmia and myocardium fibrillations.

Description

The Jameson's mamba is a fast moving, diurnal tree snake. The adult measures between 2.20 and 2.60 m in length, while hatchling are about 25 cm long. The color of its body is dull green on the dorsal side, and mottled with black and yellowish green along the lower side of body. The scales are larger and smoother on the the head, and smaller and narrowly edged with black on the rest of body. Eyes are set on the sides of head, with round pupils. The members of sub-species kaimosae, from Uganda and Kenya, has a black tail. It feeds on birds, rodents, such as squirrels and mice, and arboreal lizards. The female lays clutches of 10 and 15 eggs.

Recorded Medical Cases

A bite from a juvenile Jameson's mamba in Uganda caused considerably facial pain, chills, and sweating. This was followed by slurring of speech and incapacity to breathe. In another case, a man searching for wood to make fire in Rwanda was bitten by a green snake with a black tail; he was immediately taken to a town hospital but he died upon arrival. In Nigeria, another victim died four hours after a "green snake" bite, showing symptoms that ranged from abdominal pain, vomiting, involuntary urination, blurred vision, and inability to speak; then he was unable to breathe and died.

Below, the Jameson's mamba.

Below, the Dendroaspis jamesoni, sub-species Kaimosai.

Islets of Langerhans

The islets of Langerhans make up the endocrine portion of pancreas. They are constellations of specialized cells which secrete important hormones that regulate glucose levels in the bloodstream and metabolism. They were named after the German scientist Paul Langerhans who discovered and carefully studied them between 1869 and 1871.

Description

Each one of the islets is a mass or assemblage of endocrine cells, measuring between 50 to 500 microns in diameter. There are between 12 and 20 islets per milligram of gland tissue. In human beings and the rest of primates, they are basically composed of four types of endocrine cells; α (alpha), β (beta), δ (delta), and ε (epsilon) cells.

Alpha cells secrete glucagon. The function of glucagon is extremely important to avoid hypoglycemia, keeping sugar levels up. It induces the liver to tap the body reservoirs of fuel (glycogen and fat). This hormone is what makes you burn fat when you work out or when you are fasting. People who suffer from type I diabetes, their pancreas does not secrete glucagon and insulin.

Beta cells produce insulin, which makes the liver lower the excess glucose (sugar) in the bloodstream, converting it into glycogen, the first fuel reserve. If the sugar keeps going up, the liver cell mitochondria metabolize it into triglyceride molecules that end up in the adipose cells. This is how you become overweight. Excess insulin is deleterious (bad) over the years; thus you have to reduce your carbs consumption.

Delta cells secrete and release somatostatin, which is also produced by the hypothalamus. It inhibits the secretions of hormones, such as insulin, glucagon, somatotropin (growth hormone), and thyroid stimulating hormone.

Epsilon cells produce grhelin, which triggers hunger. It is also released by the stomach.

Brachialis Muscle

The brachialis muscle is a spindle-shaped muscle which lies deeply under the biceps brachii. It arises from the anterior surface of distal half of humerus. Then it travels downwards, stretching over the elbow-joint and fusing with its capsule, to be inserted into the tuberosity of ulna.

Action

When it contracts, the brachialis muscle flexes the forearm, pulling it towards the anterior side of arm. In this action, it works in unison (together) with the biceps brachii. It also stretches the capsule of the elbow-joint.

Innervation

It is innervated by a branch of the musculocutaneous nerve (C5-C6).

Blood Supply

This strong muscle receives oxygenated blood from the ulnar collateral, radial recurrent, and the brachial artery.

Below, picture of the brachialis muscle on the place it occupies on the arm and forearm. The biceps brachii and muscles of the forearm are absent.