General anatomy revision is important topic

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1. General anatomy Henok Alemu ( BSc and MSc )

2. INTRODUCTION TO THE HUMAN ANATOMY

3. DEFINITION OF ANATOMY The word Anatomy comes from two Greek words ( ana means apart and tomos means cutting), meaning to cut apart or to dissect. Present definition: Anatomy is a branch of science that deals with structure of the body and the relation of its parts to each other. 3

4. SUBDIVISIONS OF ANATOMY Generally Anatomy is divided in to three Macroscopic(gross anatomy ) Microscopic & Developmental Gross Anatomy (macroscopic Anatomy) : deals with structures that can be studied with out using a microscope. Microscopic Anatomy: deals with structures that are so small they can be seen with a microscope It has two sub divisions Cytology- is the study of cells Histology- is the study of tissues 4

5. Subdivisions… Developmental Anatomy: structural changes that occur in the body through out the life span and effect of aging. Embryology - study of development from the fertilized egg to adult form. studies changes that occur from conception to birth 5

6. OTHER APPLIED FIELDS OF ANATOMY Pathological Anatomy : study of structural changes (from gross to microscopic) associated with disease. Pathology: is the study of diseases. Surface Anatomy : study of the form (morphology) and markings of the surface of the body. studies structures that are located on the surface. Radiographic anatomy : the study of internal body structures by means of X-ray studies and other imaging technique. Functional morphology : explores the functional properties of body structure and assess the efficiency of their design. 6

7. APPROACHES TO STUDY ANATOMY Systemic approach Studies specific systems of the body. Classification is based on function (structures that have a common function studied together) - about 11 systems are found in human body. E.g. Integumentary Skeletal … II. Regional approach Deals with several systems located in a particular region of the body. Six regions limb (upper and lower) Back … Used mostly in dissection room and useful to physicians and surgeons. 7

8. LEVELS OF STRUCTURAL ORGANIZATION OF HUMAN BODY The human body has many levels of structural complexity. Chemical level Includes all atoms and molecules essential for maintaining life. major atoms : C,H,O,N,Ca,K & Na Molecules: proteins, carbohydrates, fats, nucleic acids (DNA, RNA) & vitamins. Atoms unite to form molecules; molecules are building blocks of the structures at cellular level. 8

9. Organization… II. Cellular level Cells are the smallest living things in the body. Cells are the basic structural and functional unit of an organism. Cells have three principal parts Plasma (cell) membrane Cytoplasm Nucleus III. Tissue level Tissues are groups of similar cells (and the substance surrounding them) that usually arise from common ancestor cells and work together to perform a particular function. 4 basic types of tissues: epithelial, muscle, connective & nervous. 9

10. Organization… IV. Organ level Organs are structures that are composed of two or more different tissues that have specific functions and usually have recognizable shape. V . System level A system consists of several related organs that have a common function. e.g. Digestive system - breakdown of food and absorption. VI. Organismic level Is the result of all of the simpler levels working in union to sustain life. 10

11. ANATOMICAL POSITION To describe body parts & their location , we need to use a common visual reference point, this reference point is called anatomical position Definition : Anatomical position is the position of a body universally used in anatomical descriptions in which the body stands erect in upright position facing the observer, with feet flat on the floor, arms placed at the sides, and the palms of the hands turned forward . Additionally the term right and left always refer to those sides belonging to the person or cadaver being viewed – not to the right and left sides of the viewer. 11

12. Level of organization 12

13. ANATOMICAL TERMINOLOGIES (terms of position and relation) Standard directional terms are used by medical personnel and anatomists to explain precisely where one body structure lies in relation to another. Anatomical terminology is less wordy and confusing. 13

14. Orientation & directional terms 14

15. Orientation & directional terms 15

16. Orientation & directional terms 16

17. BODY PLANES AND SECTIONS The body is divided by the following planes (imaginary flat surfaces ) in different sections. 1. Sagittal Plane A vertical plane that divides the body or an organ into right and left sides. Midsagittal ( median)plane: If the plane passes through the midline of the body or organ and divides it into equal right and left sides. Parasagittal plane: If the sagittal plane does not pass through the midline but instead divides the body or an organ into unequal right and left sides. 17

18. Body plane… 2 . Frontal (coronal) plane Divides the body or an organ into anterior (front) and posterior (back) portions. 3 . Transverse (cross-sectional or horizontal) plane Divides the body or organ into superior (top) and inferior (bottom) portions. The above planes are all at right angles to one another. 4 . Oblique plane Passes through the body or organ at an angle between the transverse plane and vertical plane. When we cut organs through these planes the resulting flat surfaces is termed as section. E.g. transverse (cross-sectional) plane gives transverse (cross) section. 18

19. Body plane 19

20. Body movements Body movements are described based on three axes. Longitudinal (vertical) axis: run from center of head to sole of foot is perpendicular to transverse plane Movements are: median rotation lateral rotation supination pronation 20

21. Body movement… II. Transverse (horizontal) axis: run from right to left is perpendicular to sagital plane Movements are: Flexion & E xtension Sagittal axis: run from back to front aspect of the body is perpendicular to frontal (coronal) plane Movements are : Abduction & A dduction 21

22. Skeletal system 22

23. Skeletal System Skeleton means dried up body Skeletal system is composed of bone,cartilage , joints and ligaments. Each individual bone is an organ. 23

24. Functions of Bone Support – provides hard framework that supports the wt of the body . protection Movement Blood cell formation-RBM Storage of minerals- calcium and phosphate Serve as attachment for muscles Storage of energy in the form of fats-YBM 24

25. CLASSIFICATION OF BONES Bones are classified by their shape rather than size as long, short, flat and irregular. 1 . Long bones — are considerably longer than they wide. The bones of the arms, legs, hands, and feet (but not the wrists and ankles). 2. Short bones —are roughly cubed shaped. The bones of the wrists and ankles. 3. Flat bones —thin , flattened and usually curved. The ribs, shoulder blades, and cranial bones. 4. Irregular bones — have varied shapes and many surface markings for muscle attachment e.g. the vertebrae, hip bones and facial bones. 25

26. . Sesamoid bone -is a special type of short bones. -denoting a small nodular bone embedded in a tendon or joint capsule E.g. patella or knee cap Pneumatic bone - have empty space within them   Short, flat, and irregular bones are all made of spongy bone covered with a thin layer of compact bone.   26

27. Structures of typical long bone With few exception, all bones in the body have the same general structure. diaphysis = shaft, forms the long axis of a long bone. epiphysis = one end of a long bone metaphyses are the areas between the epiphysis and diaphysis and include the epiphyseal plate in growing bones. Articular cartilage over joint surfaces acts as friction reducer & shock absorber Medullary cavity = marrow cavity 27

28. , Membrane Endosteum = lining of marrow cavity and central canals of osteons Is osteogenic- bone producing - containing bone depositing cells and bone destroying cells. Periosteum = tough membrane covering bone but not the cartilage Richly supplied by nerves and blood vessels Secured to the underlying by perforating fibers sharpey’s fiber Fibrous layer = dense irregular CT Osteogenic layer = bone cells 28

29. Structures of typical long bone 29

30. Bone (osseous) tissue Consists of widely separated cells surrounded by large amounts of extracellular matrix . Has both organic and inorganic components. Chemical Composition healthy bone is half as strong as steel in resisting compression and equally strong in resisting tension. Bone is composed of the following: 35% organic components- cells, fibers, and ground substance the organic substance particularly collagen, contribute the flexibility and tensile strength that allow bone resists stretching and twisting. 30

31. , 65% inorganic components- minerals, mostly calcium phosphate and calcium carbonate Provides bones hardness Bone is not completely solid since it has small spaces for vessels and bone marrow spongy bone has many such spaces compact bone has very few such spaces 31

32. Based on gross observation bone has two different structures: Compact -Dense outer layer that looks smooth and solid to the naked eye. outer layer provides strength. Looks like solid hard layer of bone Makes up the shaft of long bones and the external layer of all bones Resists stresses produced by weight and movement 32

33. , Spongy ( cancellous ) – consists of trabeculae (a honeycomb of small needle like), containing marrow for blood cell production or fat storage. It forms most of the structure of short, flat, and irregular bones, and the epiphyses of long bones. Spongy bone tissue is light and supports and protects the bone marrow. 33

34. Microscopic structure of bone Compact bone - is arranged in units called osteons or Haversian systems Osteons contain blood vessels, lymphatic vessels, nerves, and osteocytes along with the calcified matrix. It is a group of concentric tubes that in cross-section appear as rings. They are made up of lamella (layer of bone matrix with collagen running in one direction). 34

35. , Circular lamella is called concentric or circumferential and interstitial lamella is an incomplete lamella b/n osteons Within the lamella is a network of osteocytes embedded in lacunae and connected by canaliculi (little canals). These cells are maintained alive by nutrients and oxygen provided by blood vessels passing through the center of the osteon called the central or harvasian canal and the volkman’s canal (transverse to diaphysis) . 35

36. Microscopic structure of bone 36

37. Microscopic structure of bone Spongy bone - Latticework of thin plates of bone called trabeculae Oriented along lines of stress Made of lamella and ostecytes but not osteons because the trabeculae are so small Spaces in between these trabeculae are filled with red marrow where blood cells develop 37

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39. Bone cells Bone tissue contain 4 types of cells Osteogenic cells ( Stem cells or osteoprogenitres ) - undifferentiated cells Are found in the bone tissues in contact with the endosteum and periosteum . can divide to replace themselves & can become osteoblasts and osteoclasts found in inner layer of periosteum and endosteum Osteoblasts –are mature bone-building cells that synthesize and secret unmineralized ground substance. They are Matrix ( Unmineralized ) depositing cells Can’t divide 39

40. Bone cells Osteocytes - are mature bone cells that no longer secrete matrix Maintain structural integrity of the surrounding bone matrix. only one osteocyte is enclosed in lacunae The principal cells of bone tissue which detects strain. When an osteocyte dies, the surrounding bone matrix is reabsorbed by osteoclasts Osteoclasts (Matrix dissolving cells) are huge cells also derived from fused monocytes (WBC) Locate on resorbed surfaces of the bone matrix called Howship’s lacunae Function –are important in bone growth, remodeling and healing. in bone resorption at surfaces such as endosteum Multi nucleated 40

41. Blood and Nerve Supply of Bone Nutrient arteries - enter through nutrient foramen supplies compact bone of diaphysis & red marrow Metaphyseal & epiphyseal aa . supply red marrow & bone tissue of epiphyses Periosteal arteries - supply periosteum branches of Nutrient and epiphyseal aa 41

42. Blood and Nerve Supply of Bone 42

43. BONE FORMATION All embryonic connective tissue begins as mesenchyme. Bone formation is termed osteogenesis or ossification and begins when mesenchymal cells provide the template for subsequent ossification. Prior to week 8 Embryonic skeleton is comprised of hyaline cartilage and fibrous membranes 43

44. Cont’d Week 8 and beyond Bone tissue begins to develop Majority of fibrous or cartilaginous structures eventually replaced with bone Fibrous membrane  (membrane) bone ( Intramembranous ossification) Hyaline cartilage  (cartilage) bone ( Endochondral ossification) 44

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46. Intramembranous ossification Forms the flat bones of the skull, the mandible and clavicle. An ossification center forms from mesenchymal cells, they convert to osteoblasts and lay down osteoid matrix. The matrix surrounds the cell and then calcifies as the osteoblast becomes an osteocyte . The calcifying matrix centers join to form bridges of trabeculae that constitute spongy bone with red marrow between. On the periphery the mesenchyme condenses and develops into the periosteum 46

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48. Endochondral ossification Involves replacement of cartilage by bone and form most of the bones of the body. The first step in endochondral ossification is the development of the cartilage model . Development of Cartilage model Mesenchymal cells form a cartilage model of the bone during development 48

49. , Growth of Cartilage model in length by chondrocyte cell division and matrix formation ( interstitial growth ) in width by formation of new matrix on the periphery by new chondroblasts from the perichondrium ( appositional growth ) cells in midregion burst and change pH triggering calcification and chondrocyte death 49

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51. Endochondral ossification Development of Primary Ossification Center perichondrium lays down periosteal bone collar nutrient artery penetrates center of cartilage model periosteal bud brings nutrient artery and vein and osteoblasts and osteoclasts to center of cartilage model osteoblasts deposit bone matrix over calcified cartilage forming spongy bone trabeculae osteoclasts form medullary cavity 51

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53. Endochondral ossification Development of Secondary Ossification Center blood vessels enter the epiphyses around time of birth spongy bone is formed but no medullary cavity Formation of Articular Cartilage cartilage on ends of bone remains as articular cartilage. 53

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55. BONE GROWTH Growth in Length Bone grows in length occurs at the epiphyseal or growth plate The epiphyseal plate consists of four zones: zone of resting cartilage, zone of proliferation cartilage, zone of hypertrophic cartilage, and zone of calcified cartilage The activity of the epiphyseal plate is the only means by which the diaphysis can increase in length. 55

56. BONE GROWTH cont’d When the epiphyseal plate closes, is replaced by bone, the epiphyseal line appears and indicates the bone has completed its growth in length. Epiphyseal plate or cartilage growth plate cartilage cells are produced by mitosis on epiphyseal side of plate cartilage cells are destroyed and replaced by bone on diaphyseal side of plate Between ages 18 to 25, epiphyseal plates close. cartilage cells stop dividing and bone replaces the cartilage (epiphyseal line) Growth in length stops at age 25 56

57. Zones of Growth in Epiphyseal Plate Zone of resting cartilage - anchors growth plate to bone Zone of proliferating cartilage - rapid cell division (stacked coins) Zone of hypertrophic cartilage - cells enlarged & remain in columns Zone of calcified cartilage - thin zone, cells mostly dead since matrix calcified osteoclasts removing matrix osteoblasts & capillaries move in to create bone over calcified cartilage Ossification zone-is a region of transformation from cartilage tissue to bone tissue. 57

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59. Growth in Thickness Bone can grow in thickness or diameter only by appositional growth Two processes Osteoblasts beneath periosteum secrete bone matrix onto external bone surface Osteoclasts on endosteal surface remove bone The steps in this process are: Periosteal cells differentiate into osteoblasts which secrete collagen fibers and organic molecules to form the matrix. Ridges fuse and the periosteum becomes the endosteum . 59

60. , New concentric lamellae are formed. Osetoblasts under the periosteum form new circumferential lamellae. Osteoclasts remove the bone on endosteal surface and widen the marrow cavity only by appositional growth at the bone’s surface Periosteal cells differentiate into osteoblasts and form bony ridges and then a tunnel around periosteal blood vessel. Concentric lamellae fill in the tunnel to form an osteon . 60

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62. Bone Remodeling Remodeling is the ongoing replacement of old bone tissue by new bone tissue. Old bone is constantly destroyed by osteoclasts , whereas new bone is constructed by osteoblasts . Continual redistribution of bone matrix along lines of mechanical stress distal femur is fully remodeled every 4 months 62

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64. Fracture and Repair of Bone A fracture is any break in a bone. Healing is faster in bone than in cartilage due to lack of blood vessels in cartilage Healing of bone is still slow process due to vessel damage 64

65. , Fracture repair involves formation of a clot called a fracture hematoma , organization of the fracture hematoma into granulation tissue called a procallus (subsequently transformed into a fibrocartilaginous [soft] callus ), Conversion of the fibrocartilaginous callus into the spongy bone of a bony (hard) callus , and, finally, remodeling of the callus to nearly original form. 65

66. Cont’d Formation of fracture hematoma damaged blood vessels produce clot in 6-8 hours, after bone cells die inflammation brings in phagocytic cells for clean-up duty new capillaries grow into damaged area Formation of fibrocartilagenous callus formation ~3 weeks fibroblasts invade the procallus & lay down collagen fibers chondroblasts produce fibrocartilage to span the broken ends of the bone 66

67. Formation of bony callus Changes to spongy bone that joins 2 broken ends of bone lasts 3-4 months Bone remodeling compact bone replaces the spongy in the bony callus surface is remodeled back to normal shape 67

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69. Osteoporosis Is (bone porous condition) low bone mass due to deterioration and bone reabsorption is faster than bone deposition. Fractures occur easily, especially in the vertebrae, femur, or hip. 69

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71. Different Bone Markings - Essential Terminology Depressions and Openings A. Fissure: cleft-like opening between adjacent parts of bones through which vessels & nerves pass B. Foramen: hole through which blood vessels, nerves, ligaments can pass C. Meatus : tunnel-like passageway through a bone D. Sinus: cavity within a bone with narrow opening E. Sulcus : groove or depression that accommodates a soft structure such as vessels, nerve, tendon F. Fossa: depression in/on a bone; generally at a joint G. Process: prominent projection or point of attachment 71

72. Articular Processes (of the joints) H. Condyle : large, rounded articular (joint) prominence I. Head : rounded articular projection supported by a more constructed portion of a bone (neck) J. Facet: smooth, flat surface on a bone 72

73. Different Bone Markings - Essential Terminology Processes for Attachment (tendons, ligaments, etc.) K. Tubercle : small , rounded process L. Tuberosity : large , rounded, usually rough process M. Trochanter : large , blunt projection; only on the femur N. Line : less prominent ridge than a crest O. Spine : sharp , slender process P . Epicondyles : prominence found "above" a condyle Q. Crest : prominent ridge or elongated projection 73

74. Classification of the Bones 206 named bones of the human skeleton are grouped in to axial and appendicular skeletons in adults. At birth, the skeleton consists of approximately 270 bones. 74

75. According to their Location . A) Axial Skeleton: This is located around the longitudinal axis of the body that is most of the bones of the axial skeleton constituted the central body core of the body, the axis. 75

76. This group is composed of 80 Bones constituted by: 1- Skull a) Cranium ------ 8 b) Face ----------- 14 2- Hyoid --------------------- 1 3- Auditory Ossicles ------- 6 4-Vertebral Column ------- 26 5-Thorax a) Sternum ------1 b) Ribs ------- 24 Total 80 76

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80. B) Appendicular Skeleton : This is composed of bones found in the limbs and their corresponding girdles forming a total of 126 bones: 1- Shoulder Girdle a) Clavicle ------- 2 b) Scapula ------- 2 80

81. a) Humerus -------- 2 2- Upper Limb b) Ulna ------------ 2 c) Radius --------- 2 d) Carpals ---------16 e) Metacarpals ---10 f) Phalanges -----28 3- Pelvis Girdle Coxal , Hip, Pelvic or Innominate Bones. 81

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83. a) Femur -------------2 b) Tibia ------------- 2 4-Lower Limb c) Fibula ----------- 2 d) Patella ------------ 2 e) Tarsals --------- 14 f) Metatarsals -----10 g) Phalanges ------28 Total 126 83

84. Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones , the rib cage , the ear , the nose , the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs . It is not as hard and rigid as bone but is stiffer and less flexible than muscle . is composed of specialized cells called chondroblasts that produce a large amount of extracellular matrix . 84

85. Cartilage Consists of cells (chondrocytes) in lacunae matrix is gel like and contains collagenic and elastic fibers has no blood vessel, it receives nutrients through diffusion Three types 1 . Hyaline cartilage firm and some what flexible matrix contains many collagenic fibers Found at end of long bones (articular cartilage), in nose and at the ends of ribs 85

86. Cartilage 2. Fibro cartilage matrix contains wide rows of thick collageneous fibers able to with stand tension and pressure = found in menisci(knee joint) and discs between vertebrae 3. Elastic cartilage matrix contains elastic fibers very flexible found in epiglottis and ear flaps 86

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88. Joints These are sites where two or more bones meet The study of joints is called arthrology 88

89. Term Explanation of term Flexion Bending or decreasing the angle b/n body parts Extension Straightening or increasing the angle b/n body parts Abduction Moving away from the median plane Adduction Moving towards the median plane Rotation Moving around the long axis Circumduction Circular movement combining flexion, extension, abduction and extension Eversion Moving the sole of the foot away from the median plane Inversion Moving the sole of the foot towards the median plane Supination Rotating forearm and hand so that the palm faces anteriorly Pronation Rotating forearm and hand so that the palm faces posteriorly Protraction Moving anteriorly Retraction Moving posteriorly 89

90. Classification of joints based on their structure Joint are classified based on the presence or absence of joint cavity and kind of supportive CT surrounding the joint. Three types: fibrous, cartilaginous and synovial. 90

91. Fibrous joints Lacks a joint cavity and bones are united by fibrous connective tissue 3 types: sutures, gomphoses and syndesmoses Sutures immovable and held by thin layer of dense regular connective tissue common in skull Serrate suture – saw like articulation e.g saggital suture Squamous suture – margin of the bone overlaps with that of articulating bone e.g. squamous suture Plane suture – margins of articulating bones are fairly smooth e.g. median palatine suture 91

92. Fibrous joints . 92

93. Fibrous joints Gomphoses - unique joint between a tooth and its socket Syndesmoses - bones are united by sheet of fibrous tissue . -e.g. interosseous membrane between radius and ulna; tibia and fibula 93

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95. Cartilaginous joints Bones are united by hyaline or fibro cartilage Allow limited movement in response to twisting, compression and stress Two types Synchondroses - bones are united by hyaline cartilage Permits slight movement during early life A totally ossified synchondrosis may also be referred to as synostosis . e.g. b/n epiphysis and diaphysis symphyses - bones are united by fibrocartilage -are strong slightly movable joints -e.g. b/n vertebral bodies and pubic symphysis 95

96. Cartilaginous joints 96

97. Synovial joints most common and important one has unique features Synovial cavity Joint is freely movable Articular cartilage reduces friction Articular capsule (Fibrous capsule, synovial membrane) Ligaments - Regular tissue very strong May have adipose tissue (fat pad) Synovial fluid 97

98. Synovial joints 98

99. Types of synovial joints Plane joints -allow gliding or sliding movt ( uniaxial ) e.g. b/n scapula and clavicle b/n carpal and tarsal bones Hinge joints -permit flexion and extension only ( uniaxial ) e.g. elbow, knee and interphalangeal joints Condyloid joints -allow movement in two direction (biaxial) e.g. radiocarpal joint of the wrist and MCP joint Saddle joints - opposing surfaces of bones are like a saddle (biaxial) e.g. trapeziometacarpal at the base of the thumb (CMC joint of the thumb) Ball and socket joints - allow multidirectional movement (multi axial joint) e.g. shoulder and hip Pivot joints -allow rotation ( uniaxial joint) e.g. at atlanto axial joint, proximal radioulnar 99

100. Joints Joints can be classified according to their relative freedom of movement (function) Synarthroses - immovable Amphiarthroses - slightly movable Diarthroses - freely movable; all synovial 100

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104. Other structures associated with synovial joint: Discs and Meniscs Important for directing of a given movement in a joint For the uniform distribution of pressure on the bones Discs divide an articular cavity completely whereas meniscs divide it partly. 104

105. Synovial bursae Are small flattened fibrous bag filled with synovial fluid Found b/n the joints and their surrounding muscles, tendons, and ligaments that move on each other Reduces friction Two types Communicating Noncommunicating Articular labrum (lip) Enlarges the articular fossa to form a stable joint ( glenoidal labrum and acetabular labrum) 105

106. Ligaments Are CT structures that hold the body together Two major types of ligaments : Those that connect the viscera together Those that connect the bone together  In relation to articular capsule ligaments that connect the bone are differentiated in to three types Capsular (intrinsic) ligaments – attached to the capsule and strengthen it. Extracapsular ligs . – lie out side the capsule (collateral ligament of knee) Intracapsular ligs . – located with in the capsule (round ligament of head of femur) Both extra and intracapsular ligaments. are extrinsic ligaments Ligaments are yellow (elastic e.g. ligaments in the vertebral column) or white (provide stability, ligaments of knee joint) in color. 106

107. The Integumentary System Skin and its accessory structures, hair and nails, along with various glands, muscles and nerves make up the Integumentary system

108. Skin Functions of the skin Protect the body helps maintain a constant body temperature( regulation of body temperature) provides sensory information blood reservoir excretion and absorption synthesis of vitamin D It's highly exposed to infection, disease, and injury 108

109. Structure of the skin The skin covers the external surface of the body It is the largest organ of the body in surface area and weight Structurally, the skin consists of two principal parts Epidermis-The superficial thinner portion composed of epithelial tissue Dermis-The deeper thicker, connective tissue part 109

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112. Epidermis - is composed of keratinized stratified squamous epithelium - contains four principal types of cells Keratinocytes -(90%)-produce keratin( a tough, fibrous protein that protects the skin Melanocytes - (8%)- produce the pigment melanin Langerhans cells- destroy microbes that invade the skin Merkel cells- function for the sensation of touch 112

113. -has four strata or layers Stratum basale Stratum spinosum Stratum granulosum Stratum corneum But in thick skin there is one additional layer between stratum corneum and stratum granulosum which is known as stratum lucidum 113

114. Stratum basale - The deepest layer of the epidermis - composed of a single row of keratinocytes Stratum spinosum -Superficial to the stratum basale -8-10 layers of polyhedral keratinocytes fit close together Stratum granulosm - At the middle of the epidermis -Consists of three to five layers of flattened keratinocytes 114

115. Stratum lucidum -Found only in the thick skin (Palms and Soles) -Consists off three to five layers of clear, flat, dead keratinocytes Stratum corneum -consists of 25-30 layers of dead, flat keratinocytes -protects against injury and microbes 115

116. Dermis Mainly composed of CT containing collagen and elastic fibers The few cells present in the dermis include fibroblast, macrophages and some adiposities, Blood vessels, nerves, glands and hair follicles can be divided in to superficial papillary region and deeper reticular region 116

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118. The papillary region makes up about one-fifth of the thickness consists of areolar connective tissue containing fine elastic fibers, dermal papillae(nipple shaped projection) consists of - Capillary - touch receptor (corpuscles of touch or meissner corpuscles) - free nerve ending 118

119. The Reticular region attached to the subcutaneous layer consists of dense irregular connective tissue containing bundles of collagen, some elastic fibers, adipose cells, hair follicles, nerves, sebaceous(oil) glands and sudoriferous (sweat) gland 119

120. Skin color Melanin, carotene and hemoglobin are three pigments that give skin color Melanin - Melanocytes synthesize melanin from tyrosine ranges from yellow to reddish to brown to black - Exposure to uv light increases melanin production Melanin absorbs uv radiation and prevents damage to DNA in epidermal cells 120

121. Carotene is yellow-orange pigment obtained from tomatoes and carrots - Found in the stratum corneum , dermis and subcutaneous layer Hemoglobin is the oxygen caring protein pigment in red blood cells - gives skin red color 121

122. Accessory structures of the skin Hair present on most skin surfaces except palms and soles In adults hair is highly distributed scalp, eyebrows and around the external genitalia FUNCTION Protection decrease heat loss eye browse and eyelashes protect the eyes from foreign particles Touch receptors 122

123. Anatomy of hair Each hair is composed of columns of dead , keratinized cells bonded together by extracellular protein Hair has two parts Shaft -superficial portion of hair the part project from the skin Root -the part deep to the shaft penetrates in to the dermis and sometimes in to the subcutaneous layer -is surrounded by hair follicle 123

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125. The shaft and root both consist of 3 layers The inner= medulla Middle =cortex Outer= cuticle 125

126. Skin gland Sebaceous gland (oil gland) Connected to hair follicles Dermis Secrete an oily substance called sebum (mixture of fats, cholesterol, proteins and inorganic salts) Sudoriferous glands There are 3 to 4 million sweat glands 126

127. Nails Are plates off tightly packed, hard, keratinized epidermal cells Each nail consists of a nail body, a free edge, and a nail root Nail body -is the portion of the nail that visible -appears pink b/c of blood flowing 127

128. free edge -the part that extend past the distal end of the digits Nail root - the portion that is buried in the fold of skin The whitish, crescent-shaped area of the proximal end of the nail body is called the lunula 128

129. Types of skin Two major types of skin Thin(hairy) Thick(hairless) 129

130. Thin skin Covers all parts of the body except palm and soles Its epidermis is thin Stratum lucidum is lacking it lacks epidermal ridges It has hair follicles, arrectorpili muscle and sebaceous (oil) gland but it has fewer sweat glands 130

131. Thick skin covers the palms and soles It’s epidermis is relatively thick(0.6-4.5 mm) has epidermal ridges lacks hair follicles, arrectorpili muscles and sebaceous gland and has more sweat gland 131