Self Assessment and Review of Anatomy PDF
Preview Self Assessment and Review of Anatomy
Rajesh K Kaushal MD Anatomy (AIIMS, Delhi) Director, Human Anat Academia New Delhi The Health Sciences Publisher New Delhi | London | Panama Self Assessment and Review of Anatomy First Edition: Digital Version 2018 © Digital Version 2018, Jaypee Brothers Medical Publishers It all begins with one word Passion ! Dedicated to Long ago I thought of a mission—Human Anatomy Made Simple. Then it was a dream, now realizing that dream into concrete reality is a profound matter of satisfaction and joy. As Steve Maraboli mentioned: ‘The best way to succeed is to have a specific Intent, a clear Vision, a plan of Action, and the ability to maintain Clarity.’ Anatomy is an integral component of PG Entrance exams at multiple levels. It is not an important individual subject in itself but, in terms of conceptual and clinical correlates, touches and fetches improved scoring in almost all the major and minor subjects, once mastered well. The present book is a simplistic quintessential approach to master basic and conceptual Anatomy and its clinical application. Maximum possible content has been covered under various sub-sections of Anatomy, so that the student does not need to look into a plethora of books—in a sense it is ‘all in one approach’. It is written in a simple lucid language with neatly labelled line diagrams, along with tables and flowcharts to improve memorization and recall of the vast content. The latest edition of Gray’s Anatomy has abundance of updated information, which is not in accordance with the traditional/conventional teaching. Such information has been included in the present book but its usage in the exams is not yet advisable, and depends upon the discretion of the teacher and the students. Controversies arise when different authors follow different standard textbooks, for example, a particular question on pemphigus vulgaris may be asked by Anatomy department, but may also interest, Pathology, Dermatology and Medicine departments equally. Such questions have been dealt with profound and relentless research, referring to respective department standard textbooks and Journals to bring you the most appropriate answer possible. Dear students, I was a medical student, and will remain so throughout my life. We all have been trained to work hard in the best interest of our patients and peers. I respect and honour your tenacity in keeping the fire and zeal alive in your heart and mind, and remain highly motivated despite tough scenarios in life keep presenting in front of you, every possible moment. Wishing a great success to all the students, in all arenas of life ! Rajesh K Kaushal MD Anatomy (AIIMS, Delhi) PREFACE I would like to thank Shri Jitendar P Vij (Group Chairman), Mr Ankit Vij (Group President) and Mrs Chetna Malhotra Vohra (Associate Director–Content Strategy) of Jaypee Brothers Medical Publishers (P) Ltd. New Delhi, India, for enabling me to publish this book. I would also like to thank Ms Payal Bharti (Project Manager), and the complete Production Team for helping me in the whole process. ACKNOWLEDGMENTS 1. General Anatomy 1 2. Embryology 20 3. Histology 148 4. Neuroanatomy 224 5. Head and Neck 334 6. Back 540 7. Thorax 555 8. Upper Limb 627 9. Abdomen 725 10. Pelvis 847 11. Lower Limb 902 1. General Anatomy 1 2. Embryology 20 3. Histology 148 4. Neuroanatomy 224 5. Head and Neck 334 6. Back 540 7. Thorax 555 8. Upper Limb 627 9. Abdomen 725 10. Pelvis 847 11. Lower Limb 902 CONTENTS SKELETON Parts of Bone Bone is a calcified connective tissue consisting of cells (osteocytes) embedded in a matrix of ground substance and collagen fibers. ● It has a superficial thin layer of compact bone around a central mass of spongy bone, and contain internal soft tissue, the marrow, where blood cells are formed. ● It serve as a reservoir for calcium and phosphorus and act as biomechanical levers on which muscles act to produce the movements permitted by joints. Long bones have a shaft (diaphysis) and two ends (epiphyses). The metaphysis is a part of the diaphysis adjacent to the epiphyses. ● Diaphysis Dž Forms the shaft (central region) and is composed of a thick tube of compact bone that encloses the marrow cavity. ● Metaphysis Dž Is a part of the diaphysis, the growth zone between the diaphysis and epiphysis during bone development. ● Epiphyses Dž Are expanded articular ends, separated from the shaft by the epiphyseal plate during bone growth and composed of a spongy bone surrounded by a thin layer of compact bone. Bones in the Body ● Bony skeleton consists of 206 bones and is divided into two parts: the axial skeleton and the appendicular skeleton. ● Axial skeleton is the central core unit, consisting of the skull, vertebrae, ribs, and sternum. ● Appendicular skeleton comprises the bones of the extremities. Table 1: Number of bones present in axial and appendicular skeleton Number of bones Axial skeleton Appendicular skeleton 1. Skull 2. Pectoral (shoulder) girdles 3. Pelvic (hip) girdle Cranial bones 8 Clavicle 2 Hip bone 2 Facial bones 14 Scapula 2 Lower limbs Hyoid 1 Upper limbs Femur 2 Ear ossicles (3 in each ear) 6 Humerus 2 Fibula 2 Vertebral bones 26 Ulna 2 Tibia 2 Rib cage Radius 2 Patella 2 Sternum 1 Carpals 16 Tarsals 14 Ribs 24 Metacarpals 10 Metatarsals 10 Phalanges 28 Phalanges 28 Total 80 Total 60 Total 66 Number of bones Total bones of axial skeleton 80 Total bones of appendicular skeleton 60 + 66 Total bones of the body 206 General Anatomy CHAPTER 1 Self Assessment and Review of Anatomy 2 Sesamoid Bones Sesamoid bones develop in certain tendons and reduce friction on the tendon, thus protecting it from excessive wear. ● They are commonly found where tendons cross the ends of long bones in the limbs. ● Sites of sesamoid bones: Dž In the ear: The lenticular process of incus is a sesamoid bone and therefore is considered the fourth ossicle of middle ear. Dž In the hand: Two sesamoid bones in the distal portions of the first metacarpal bone (within the tendons of adductor pollicis and flexor pollicis brevis). Dž In the wrist: The pisiform of the wrist is a sesamoid bone (within the tendon of flexor carpi ulnaris), develops at age 9–12. Dž In the knee: The patella (within the quadriceps tendon) Dž Fabella in the lateral head of gastrocnemius behind the knee joint. Dž Sesamoid bone in the tendon of peroneus longus where it binds around the cuboid bone. Dž In the foot: Two sesamoid bones in the distal portions of the first metatarsal bone (within the tendons of flexor hallucis brevis. Pneumatic Bones Note: Pneumatic bones are the irregular bones which contain air-filled cavities within them. ● They are generally produced during development by excavation of bone by pneumatic diverticula (air sacs) from an air- filled space such as the nasal cavity. ● E.g., maxilla, frontal, sphenoid, and ethmoid bones and a part of the mastoid process of the temporal bone. Note: At birth the mastoid is not pneumatized, but becomes aerated over the first year of life. Ossification ● Ossification is the process of laying down new bone material by cells called osteoblasts. It is of two types: Dž Membranous ossification is the direct laying down of bone into the mesenchyme (embryonic connective tissue). Dž Endochondral ossification involves osteogenesis in a precursor model of cartilage. ● Membrane (dermal) bones ossify in membrane (intramembranous ossification), and are thus derived from mesenchymal condensations. The flat bones of the skull and face, the mandible, and the clavicle develop by intramembranous ossification. ● Cartilaginous bones ossify in cartilage (endochondral ossification), and are thus derived from preformed cartilaginous models. The bones of the extremities (limbs) and those parts of the axial skeleton that bear weight (vertebral column and thoracic cage) develop by endochondral ossification. ● Membrano-cartilaginous bones are initially formed in membrane but later partly in cartilage. Examples: clavicle, mandible, occipital, temporal, sphenoid. ● Cartilaginous ossification involves primary and secondary centres of ossification: ● Primary center of ossification Dž In long bones, bone tissue first appears in the diaphysis (middle of shaft). Dž Primary centres starts appearing at week 6 of intrauterine life. Dž Chondrocytes multiply and form trabeculae and cartilage is progressively eroded and replaced by bone, extending towards the epiphysis. Dž A perichondrium layer surrounding the cartilage forms the periosteum, which generates osteogenic cells that make a collar to encircles the exterior of the bone and remodels the medullary cavity on the inside. Dž The nutrient artery enters via the nutrient foramen from a small opening in the diaphysis. It invades the primary centre of ossification, bringing osteogenic cells (osteoblasts on the outside, osteoclasts on the inside.) The canal of the nutrient foramen is directed away from more active end of bone when one end grows more than the other. When bone grows at same rate at both ends, the nutrient artery is perpendicular to the bone. Dž Secondary center of ossification The secondary centres generally appear at the ends (epiphysis) of long bones. Secondary ossification mostly occurs after birth except for secondary centers around knee joint (distal femur and proximal tibia), which appear during last weeks of fetal life (or immediately after birth). The epiphyseal arteries and osteogenic cells invade the epiphysis, depositing osteoblasts and osteoclasts which erode the cartilage and build bone. This occurs at both ends of long bones but only one end of digits and ribs. Ossification centers which appear prenatally (ossified at birth) are: diaphysis of long bones, skull bones, vertebral column, ribs and sternum, few foot bones (talus, calcaneum, cuboid). Primary center of all carpal and tarsal bones (except talus, calcaneum and cuboid) appear after birth. General Anatomy 3 A B Fig. 1: Ossification of a long bone Figs. 2A and B: Growth of bone—lengthwise: (A) Four zones of epiphyseal cartilage, (B) Conversion of calcified cartilage into bone Time period Bones affected Second month of fetal development Ossification in long bones beginning Fourth month Most primary ossification centers have appeared in the diaphyses of bone. Birth to 5 years Secondary ossification centers appear in the epiphyses 5 years to 12 years in females, 5 to 14 years in males Ossification is spreading rapidly from the ossification centers and various bones are becoming ossified 17 to 20 years Bone of upper limbs and scapulae becoming completely ossified 18 to 23 years Bone of the lower limbs and os coxae become completely ossified 23 to 25 years Bone of the sternum, clavicles, and vertebrae become completely ossified By 25 years Nearly all bones are completely ossified Growing End ● The growing ends of bones in upper limb are upper end of humerus and lower ends of radius and ulna. ● In lower limb, the lower end of femur and upper end of tibia are the growing ends. ● The nutrient foramen is directed away from the growing end of the bone; their directions are indicated by a memory aid: ‘Towards the elbow I go, from the knee I flee’. Fig. 3: Parts of a young long bone Fig. 4: Direction of nutrient foramina in the limb bones Fig. 5: Arterial supply of a long bone. The upper epiphysis (growing end) has not yet fused with the diaphysis Blood Supply Nutrient artery enters the diaphysis (shaft) through the nutrient foramen, runs obliquely through the cortex, and divides into ascending and descending branches in the medullary cavity. ● Each branch divides into a number of small parallel channels which terminate in the adult metaphysis by anastomosing with the epiphysial, metaphysial and periosteal arteries. ● It supplies medullary cavity, inner 2/3 of cortex and metaphysis. ● The nutrient foramen is directed away from the growing end of the bone. Memory aid: Towards the elbow I go, from the knee I flee. Self Assessment and Review of Anatomy 4 ASSESSMENT QUESTIONS 1. Bones ossified at birth: (PGIC 2015) a. Lower end of femur b. Calcaneum c. Upper end of tibia d. Upper end of humerus e. Lower end of humerus 2. Endochondral ossification is/are seen in: (PGIC 2015) a. Long bones b. Flat bones of skull c. Clavicle d. Mandible e. Nasal bones 3. Nutrient artery runs: (NEET Pattern 2012) a. Towards metaphysis b. Away from metaphysis c. Away from epiphysis d. None ANSWERS WITH EXPLANATIONS 1. a. Lower end of femur; b. Calcaneum; c. Upper end of tibia • Secondary centers around knee joint (distal femur and proximal tibia) appear during last weeks of intrauterine life (or immediately after birth). • Primary center of all tarsal bones (except talus, calcaneum and cuboid Appear after birth. 2. a. Long bones • Long bones develop by endochondral ossification, whereas bones of skull; facial skeleton; mandible; clavicle bone develop by membranous ossification. 3. a. Towards metaphysis • Nutrient artery enters the shaft (diaphysis) of the bone, divides into ascending and descending branches, which run towards and terminate in the adult metaphysis by anastomosing with the epiphyseal, metaphyseal and periosteal arteries. Epiphysis There are four types of epiphysis: ● Pressure epiphysis are the parts of bone involved in weight transmission (and are intracapsular) for e.g. head of humerus and femur and condyles of humerus, femur, tibia etc. A B C D Figs. 6A to D: Types of epiphyses: (A) Pressure and traction epiphyses. (B) and (D) Atavistic epiphyses. (C) Aberrant epiphysis ● Traction epiphysis are present at the ends of bones and develop due to traction by the attached muscles (and are therefore extracapsular), e.g. greater (and lesser) tubercles in humerus and greater (and lesser) trochanter in femur. Dž These epiphyses ossify later than pressure epiphyses. Dž Examples of traction epiphyses are tubercles of the humerus (greater tubercle and lesser tubercle), and trochanters of the femur (greater and lesser). Mastoid process is also a traction epiphysis. ● Atavistic epiphysis: These types of fused bones are called atavistic, e.g. the coracoid process of the scapula, which has been fused in humans with the main bone, but is separate in lower animals. ● Aberrant epiphysis: These epiphyses are deviations from the normal anatomy and are not always present. For example, the epiphysis at the head of the first metacarpal bone, posterior tubercle of talus ( as trigonum). ASSESSMENT QUESTIONS 1. Which of the following is a traction epiphysis? a. Tibial condyles (NEET Pattern 2012) b. Trochanter of femur c. Coracoid process of scapula d. Head of femur 2. Traction epiphysis is/are: (PGIC) a. Head of humerus b. Lesser tubercle c. Deltoid tuberosity d. Coracoid process e. Greater trochanter General Anatomy 5 3. Which of the following is aberrant epiphysis? a. Coracoid process (NEET Pattern 2015) b. Greater tubercle of humerus c. Base of 1st metacarpal d. Base of 2nd metacarpal 4. Mastoid process is which type of epiphysis? a. Pressure (NEET Pattern 2015) b. Aberrant c. Atavistic d. Traction ANSWERS WITH EXPLANATIONS 1. b. Trochanter of femur • Trochanter of femur is an example of traction epiphysis and is extracapsular. • Tibial condyles and head of femur are under the pressure epiphysis category and are intracapsular. • Coracoid process of scapula is an example of atavistic epiphysis. 2. b. Lesser tubercle; e Greater trochanter. • Traction epiphysis are present at the ends of bones and develop due to traction by the attached muscles (and are therefore extracapsular), e.g. Greater (and lesser) tubercles in humerus and greater (and lesser) trochanter in femur. • Pressure epiphysis are involved in weight transmission (and are intracapsular) for e.g. head of humerus and femur and condyles of humerus, femur, tibia etc. • Coracoid process in scapula is an example of atavistic epiphysis. • Deltoid tuberosity is not an epiphysis (it is present on the shaft/diaphysis). 3. d. Base of 2nd metacarpal • Aberrant epiphyses are deviations from the normal anatomy and are not always present. For example, the epiphysis at the head of the first metacarpal bone and at the bases of other metacarpals. 4. d. Traction • Traction epiphysis are present at the ends of bones and develop due to traction by the attached muscles (and are therefore extracapsular). • Mastoid process is produced due to the traction by the sternocleidomastoid muscle. Miscellaneous ASSESSMENT QUESTIONS 1. All of the following statements are true for metaphysis of bone EXCEPT: (AIPG 2003) a. It is the strongest part of bone b. It is the most vascular part of bone c. Growth activity is maximized here d. It is the region favoring hematogenous spread of infection 2. All of the following statements are true for metaphysis of bone EXCEPT: (AIPG 2003) a. It is the epiphyseal end of diaphysis b. Growth activity is negligible here c. It is highly vascular d. Common site of osteomyelitis in children 3. TRUE statement is: (AIPG 2000) a. Osteoblasts give rise to osteocytes b. Growth of bone occurs at diaphysis c. Epiphysis is present between metaphysis and diaphysis d. Interphalangeal joint is a saddle joint 4. Pisiform is which type of bone? (NEET Pattern 2015) a. Pneumatic bone b. Sesamoid bone c. Accessory bone d. Long bone 5. All of the following are pneumatic bones EXCEPT: a. Frontal (AIPG 2011) b. Ethmoid c. Mandible d. Maxilla 6. Bone which is pneumatic: (PGIC May 2015) a. Maxillary b. Parietal c. Temporal d. Frontal e. Ethmoidal ANSWERS WITH EXPLANATIONS 1. a. It is the strongest part of bone • The strongest part of bone is diaphysis (not metaphysis). • During growth of bone maximum activity occurs at growth plate (physis) and metaphysis. • Metaphysis is the most vascular part of bone and most prone for lodging of the infectious agent in hematogenous infection. 2. b. Growth activity is negligible here • Metaphysis is the epiphyseal end of the diaphysis. • Growth activity is maximum at the growth plate (physis) and metaphysis. • Metaphysis is richly supplied with arteries forming hairpin bends, hence becomes a common site of osteomyelitis in children, as infectious agent are easily trapped in sluggish blood flow in hairpin bends. 3. a. Osteoblasts give rise to osteocytes • Osteoblasts that get trapped in Haversian lamellae become osteocyte and assume the function of bone maintenance. They are no longer involved in bone formation. • Growth activity is maximum at the growth plate (physis) and metaphysis. • Metaphysis is present between diaphysis and epiphysis. • Interphalangeal joint is a hinge variety of synovial joint.
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