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REPRODUCTION

DIFFERENTIATION OF GONADS FACTORS INFLUENCING NORMAL AND ABNORMAL GONADAL DIFFERENTIATION Whether the primordial gonad differentiates as a testis or as an ovary is determined by genetic information coded on the X and Y chromosomes. The differentiation of all the other anatomic and functional features that distinguish male from female stem secondarily from the effect of testicular or ovarian secretions on their respective primordial structures. The Y…

ADRENAL

Plate 3-1 Open full size image DEVELOPMENT OF THE ADRENAL GLANDS The detailed anatomy of the adrenal glands was first described by Bartholomeo Eustacius in 1563. Each adrenal gland consists of two parts—the cortex and medulla—that are enveloped in a common capsule. The cortex is derived from mesenchymal tissue and the medulla from ectodermal tissue. From the fifth to sixth week of embryogenesis, the cortical portion…

THYROID

ANATOMY OF THE THYROID AND PARATHYROID GLANDS Located between the larynx and the trachea medially and the carotid sheath and the sternomastoid muscles laterally, the thyroid gland weighs 15 to 25 g. The lateral thyroid lobes are 3 to 4 cm long and 1.5 to 2 cm wide; the isthmus is 1.2 to 2 cm long and 2 cm wide and crosses the trachea between the…

PITUITARY AND HYPOTHALAMUS

DEVELOPMENT OF THE PITUITARY GLAND The pituitary gland, also termed the hypophysis , consists of two major components, the adenohypophysis and the neurohypophysis. The adenohypophysis (anterior lobe) is derived from the oral ectoderm, and the neurohypophysis (posterior lobe) is derived from the neural ectoderm of the floor of the forebrain. A pouchlike recess—Rathke pouch—in the ectodermal lining of the roof of the stomodeum is formed by…

Stomach

Development of Stomach and Greater Omentum The foregut begins as a simple, midline, tubular structure lined by epithelium derived from endoderm. While the endoderm creates the lining of the stomach, the visceral mesoderm that surrounds it will form the muscles, connective tissues, and mesenteries that are associated with the organ. The portion of the foregut that will become the stomach first starts to expand in the…

Esophagus

Development of Esophagus The esophagus is the first section of the foregut and begins at the distal end of the pharynx. As with the rest of the digestive tract, the cells that line the lumen of the esophagus are derived from endoderm. The supporting structures of the esophagus come from two different sources, although they are all innervated by the vagus nerve. The muscles and connective…

Mouth and Pharynx

Development of Mouth and Pharynx The lining of the primitive gut tube is derived from the embryonic endoderm and the supporting tissues and mesentery from the visceral layer of lateral plate mesoderm. The amniotic cavity expands around the developing embryo to create the body wall but leaves the endoderm/ectoderm connection at the oropharyngeal membrane and caudally at the cloacal membrane. The early mouth, stomodeum, is formed…

Overview of Upper Digestive Tract

Development of Gastrointestinal Tract We will take a very short tour of early development prior to the trilaminar embryo stage, at which time we will follow the development of the gastrointestinal tract in detail. Thereafter, for each region of the gastrointestinal tract, we will begin with a short summary of the specific embryology relevant to the structures in that region. The single-celled zygote begins dividing roughly…

Colon

Development of Large Intestine The development of the large intestine is intimately tied to the development of other organs. The cecum, appendix, ascending colon, and transverse colon are part of the midgut and develop alongside the jejunum and ileum. The descending colon, sigmoid colon, and rectum are hindgut structures and develop in conjunction with the urogenital system. During normal development, the midgut elongates tremendously and herniates…

Small Bowel

Development of Small Intestine The small intestine includes the duodenum, jejunum, and ileum. During development of the gastrointestinal system, the duodenum comes from the distal portion of the foregut, whereas the jejunum and ileum come entirely from the midgut. The duodenum moves to the right of the midline as the stomach rotates and shifts to the left side of the abdomen during weeks 4 to 6…

Overview of Lower Digestive Tract

Blood Supply of Small and Large Intestines The blood supply to the small and large intestines is extremely variable and unpredictable. The variations concerning the origin, course, anastomoses, and distribution of the intestinal vessels are so frequent and so significant that conventional textbook descriptions are inadequate and, in many respects, even misleading, a situation much the same as that of the blood supply of the upper…

Pancreas

Development of Pancreas The foregut is the first segment of the gut tube within the abdomen. It is attached to the anterior body wall by a ventral/anterior mesentery and posteriorly by a dorsal/posterior mesentery, the latter distributing blood from the dorsal aorta via the celiac arterial trunk. Two diverticula extend from the foregut, one dorsally and the other ventrally. The dorsal pancreatic bud extends into the…

Gallbladder and Bile Ducts

Development of Gallbladder and Bile Ducts The foregut is the first segment of the gut tube within the abdomen. It is attached to the anterior body wall by a ventral/anterior mesentery and posteriorly by a dorsal/posterior mesentery, the latter supplying blood from the dorsal aorta via the celiac arterial trunk. Two diverticula extend from the foregut, one dorsally and the other ventrally. The dorsal pancreatic bud…

Liver

Development of Liver The foregut is the first segment of the gut tube within the abdomen. It is attached to the anterior body wall by a ventral/anterior mesentery and to the posterior wall by a dorsal/posterior mesentery, the latter supplying blood from the dorsal aorta via the celiac arterial trunk. Two diverticula extend from the foregut, one dorsally and the other ventrally. The dorsal pancreatic bud…

Study Guides

1 Head and Neck Study Guide 1.1 Topographic Surface Anatomy Study Aims At the end of your study, you should be able to: Identify the key landmarks in the midline of the neck and their significance State the structures that are situated at the level of C6 Outline the boundaries of the triangles of the neck Describe the landmarks for palpation of the main arteries, which…

Plate Pearls

Section 1 Introduction Plates 1–21 Plate 1 Body Planes and Terms of Relationship This plate summarizes anatomical planes of study and terms of anatomical relationship. Note that in these images, the subject is always in a consistent anatomical position, with the head and toes directed anteriorly and the arms lateral to the trunk with the palms facing anteriorly. The left image shows three key anatomical planes of study:…

Lower Limb

Surface Anatomy 491‒494 Hip, Buttock, and Thigh 495‒515 Knee 516‒523 Leg 524‒534 Ankle and Foot 535‒549 Nerves 550‒554 Regional Imaging 555‒556 Structures with High Clinical Significance Tables 8.1‒8.2 Nerves of Lumbosacral Plexus Tables 8.3‒8.4 Muscles Tables 8.5‒8.8 Electronic Bonus Plates BP 103‒BP 112 Electronic Bonus Plates BP 103 Arteries of Knee and Foot BP 104 Cross-Sectional Anatomy of Hip: Axial View BP 105 Arteries of Thigh…

Upper Limb

Surface Anatomy 422‒426 Shoulder and Axilla 427‒439 Arm 440‒445 Elbow and Forearm 446‒461 Wrist and Hand 462‒481 Nerves and Vasculature 482‒489 Regional Imaging 490 Structures with High Clinical Significance Tables 7.1‒7.2 Nerves of Brachial Plexus Tables 7.3‒7.4 Muscles Tables 7.5‒7.8 Electronic Bonus Plates BP 96‒BP 102 Electronic Bonus Plates BP 96 Arteries of Arm and Proximal Forearm BP 97 Arteries of Forearm and Hand BP 98…

Pelvis

Surface Anatomy 352 Bony Pelvis 353‒357 Pelvic Diaphragm and Viscera 358‒368 Urinary Bladder 369‒371 Female Internal Genitalia 372‒376 Female Perineum and External Genitalia 377‒380 Male Perineum and External Genitalia 381‒388 Homologies of Male and Female Genitalia 389‒390 Male Internal Genitalia 391‒392 Rectum and Anal Canal 393‒399 Vasculature 400‒410 Nerves of Perineum and Pelvic Viscera 411‒419 Cross-Sectional Anatomy 420‒421 Structures with High Clinical Significance Tables 6.1‒6.3 Muscles…

Abdomen

Surface Anatomy 267 Abdominal Wall 268‒287 Peritoneal Cavity 288‒293 Stomach and Intestines 294‒301 Liver, Gallbladder, Pancreas, and Spleen 302‒307 Visceral Vasculature 308‒318 Visceral Nerves and Plexuses 319‒329 Kidneys and Suprarenal Glands 330‒343 Lymphatics 344 Regional Imaging 345‒346 Cross-Sectional Anatomy 347‒351 Structures with High Clinical Significance Tables 5.1‒5.3 Muscles Table 5.4 Electronic Bonus Plates BP 53‒BP 83 Electronic Bonus Plates BP 53 Inguinal and Femoral Regions BP…