Skin Anatomy PDF

 Definition: It is the structure that covers the body and protects it from the environment.  It is formed of two layers: 1. Epidermis (superficial layer). 2. Dermis (deep layer). Epidermis: – On the palms of the hands and the soles of the feet, the epidermis is extremely thick,...

 Definition: It is the structure that covers the body and protects it from the environment.  It is formed of two layers: 1. Epidermis (superficial layer). 2. Dermis (deep layer). Epidermis: – On the palms of the hands and the soles of the feet, the epidermis is extremely thick, to withstand the wear and tear that occurs in these regions. – In other areas of the body, for example, on the anterior surface of the arm and forearm, it is thin. Dermis: – The dermis contains many blood vessels, lymphatic vessels and nerves. – It shows considerable variation in thickness in different parts of the body, tending to be thinner on the anterior than on the posterior surface. – It is thinner in women than in men. – The dermis of the skin is connected to the underlying deep fascia or bones by the superficial fascia, otherwise known as subcutaneous tissue. 1  Skin Lines: 1. Flexure lines (Skin creases): – They are folds of the skin over joints. – At these sites, the skin is thinner than elsewhere and is firmly tethered to underlying structures by strong bands of fibrous tissue. 2. Papillary ridges: – They are confined to palms and soles and the flexor surfaces of the digits. – They form narrow ridges separated by fine parallel grooves. 3. Wrinkle lines: – They are lines caused by contraction of the underlying muscles. – On the face they are known as lines of expression which become permanent with aging due to loss of skin elasticity. 4. Langer (tension) lines: – They represent skin tension in rigor mortis and correspond to the orientation of collagen in the dermis. – Surgical incisions made parallel to them heal with a minimum of scar tissue. 2  Functions of the skin: 1. Protection of the deep structures against micro-organisms and external injury. 2. Prevention of fluid loss. 3. Regulation of body temperature by secretion of sweat glands. 4. Sensation (pain, touch & temperature) by nerve endings. 5. Moistening of skin by secretion of fat from sebaceous glands. Skin appendages 1. Nails Nails Keratinized plates on the dorsal surfaces of the tips of the fingers and toes. Root of the nail The proximal edge of the plate. Nail folds Folds of skin that surround the nail except the distal edge of the plate. Nail bed The surface of skin covered by the nail. 3  2. Hairs & Hair follicles Hair – Derivative of the epidermis. – Consists of two distinct parts: 1. Hair follicle. 2. Hair shaft. Hair follicle – Sac from which a hair grows and into which the sebaceous glands open. – It anchors each hair into the skin. Hair shaft – Consists of a cortex, cuticle cells and a medulla for some types of hairs. Hair bulb – The concave base of the hair follicle. – The concavity is occupied by vascular hair papilla.  Sites with no hair: 1. Lips. 2. The palms of the hands. 3. The sides of the fingers. 4. The glans penis and clitoris. 5. The labia minora and the internal surface of the labia majora. 6. The soles and sides of the feet and the sides of the toes. 4  3. Sebaceous glands  Site: – On the sloping undersurface of the follicles and lie within the dermis.  Function: They pour their secretion (sebum) onto the shafts of the hairs as they pass up through the necks of the follicles. Sebum is an oily material that: – Helps preservation of the flexibility of the emerging hair. – Oils the surface epidermis around the mouth of the follicle. 4. Sweat glands ▪ They are long, spiral, tubular glands.  Site: – Distributed over the surface of the body. – Extend through the full thickness of the dermis. – Their extremities may lie in the superficial fascia. – The most deeply penetrating structures of all the epidermal appendages.  Sites with no sweat glands: 1. The red margins of the lips. 2. The nail beds. 3. The glans penis and clitoris. 5  Definition: It is a band or sheet of connective tissue, primarily collagen. Beneath the skin that attaches, stabilizes, encloses, and separates muscles and other internal organs. The fasciae of the body can be divided into two types (superficial & deep).  Site: Lie between the skin and the underlying muscles and bones. 1. Superficial fascia (subcutaneous tissue)  Structure: ▪ Mixture of loose areolar and adipose tissue. ▪ Connects the dermis of the skin to the underlying deep fascia. In the scalp, back of the neck, It contains numerous bundles of collagen fibers that palms, and soles: hold the skin firmly to the deeper structures. In the eyelids, auricle of the ear, It is devoid of adipose tissue. penis and scrotum, and clitoris: In the anterior abdominal wall: It is differentiated into superficial fatty layer and deep membranous layer.  Functions: 1. It gives certain parts of the body their specific contour as in buttock and breast. 2. It acts as heat insulator by preventing excess heat loss. 3. It is a source of energy. 4. It acts as a medium for the passage of cutaneous nerves and vessels. 6  2. Deep Fascia ▪ It is a membranous layer of connective tissue. ▪ Invests the muscles and other deep structures.  Different names and forms of the deep fascia: ❖ In the neck: – It forms well-defined layers that important in determining the path taken by pathogenic organisms during the spread of infection. ❖ In the thorax & abdomen: – It is merely a thin film of areolar tissue covering the muscles and aponeuroses. ❖ In the limbs: – It forms a definite sheath around the muscles and other structures holding them in place. – Fibrous septa extend from the deep surface of the membrane, between the groups of muscles, divides the interior of the limbs into compartments. ❖ In the region of joints: – Thickened to form restraining bands called retinacula.  Functions: 1. It holds underlying tendons in position or serves as pulleys around which the tendons may move. 2. It invests the deep structures to bone. 3. It gives the origin and insertion of some muscles. 4. It sends septa to bone forming compartments. 5. It forms retinacula to hold the long tendons. 6. It protects the palm and sole by forming palmar and plantar aponeuroses. 7  MCQ 1. Which layer of the skin does NOT contain 9. Oily mineral preserves the flexibility of blood vessels: emerging hair: a. Epidermis. a. Sebum. b. Subcutaneous tissue. b. Fat. c. Dermis. c. Sweat. 2. Deep fascia is connected to the dermis by: d. Blood. a. Epidermis. 10. The most deeply structure of epidermal b. Subcutaneous tissue. appendages is: c. Sebaceous glands. a. Hair. d. Sweat glands. b. Sebaceous gland. 3. Folds of skin over the joints: c. sweet gland. a. Skin creases. d. Nail. b. Papillary ridges. 11. The ________ acts as an insulator for the c. Tension line. body. d. Wrinkle line. a. Sebaceous gland. 4. Narrow ridges separated by fine parallel b. Deep fascia. grooves: c. Hypodermis. a. Skin creases. d. Dermis. b. Papillary ridges. 12. A deep band or sheath of connective tissue c. Tension line. invests, enclose, stabilizes and separates the d. Wrinkle line. muscles or the bone: 5. Lines caused by muscular contraction: a. Sebaceous gland. a. Skin creases. b. Deep fascia. b. Papillary ridges. c. Hypodermis. c. Tension line. d. Dermis. d. Wrinkle line. 13. Holding the underlying structure and serves 6. Skin lines is represented in rigor mortis and as pulleys around which the tendon may corresponding to the orientation of collagen: move: a. Skin creases. a. Sebaceous gland. b. Papillary ridges. b. Deep fascia. c. Tension line. c. Hypodermis. d. Wrinkle line. d. Dermis. 7. Surgical incision made parallel to them: 14. Which of the following is devoid of adipose a. Skin creases. tissue? b. Papillary ridges. a. Scalp. c. Tension line. b. Palm of hand. d. Wrinkle line. c. Abdominal wall. 8. Which of the following sites with sweat d. Scrotum. glands: 15. Separate bones to compartment: a. Lips. a. Septa. b. Glans penis and clitoris. b. Retinacula. c. Palm of the hand. c. Aponeurosis. d. Nail bed. d. Sebum 16. Holding the long tendons: a. Septa. b. Retinacula. c. Aponeurosis. 1. a 2. b 3. a 4. b 5. d 6. c 7. c 8. c 9. a 10. c 11. c 12. b 13. b 14. d 15. a 16. b 8  Skeleton: – The bony built that characterizes the shape of human being. – It is composed of two types of tissues (cartilage & bone). Cartilage: – It is the temporary skeleton of the developing fetus that is gradually and almost replaced by bone by the process of ossification. – It is softer, less rigid and slightly elastic in comparison with bone. ▪ In certain sites of the body, it persists throughout life as in. 1. The articular surfaces of most of the bones. 2. Costal cartilage. 3. Air passages as the nasal, laryngeal, tracheal and bronchial cartilages. 4. External ear. 17  Bone: – Modified types of connective tissue. – Being consist of cells (osteocytes), fibers and matrix. – They have hard consistency due to calcification of its extracellular matrix. – They are classified according to their forms (structure), development, shape, or site in the body.  Types (classification) of the bone: According to shape (morphological classification): 1. Long bones: – They have two ends and shafts. – Long bones of upper and lower limbs; femur, tibia, fibula, humerus, radius and ulna. 2. Short bones: – They are cubical in shape. – Carpal bones of hand and tarsal bones of foot. 3. Flat bones: – Thin plate of bones. – As vault of skull and scapula. 4. Irregular bones: – They have no definite shape. – As vertebrae and bones of base of skull. 5. Pneumatic bones: – They are bones containing air. – As paranasal sinuses of skull. 18 6. Sesamoid bones: – They are nodules of bones lying inside tendons of some muscles. – As patella. 7. Sutural bones: – Small bones lying inside sutures of skull. According to development (embryological classification): 1. Membranous ossification: It occurs in bones required quickly for support or protection of essential organs as those of the vault of skull and face. 2. Cartilaginous ossification: At first a model of the future bone is formed from cartilage. Then ossified in two steps: A. Primary centers of ossification: – Appear during the fetal life in the middle of shaft of bone. – As ossification propagates the shaft is transformed to the diaphysis, leaving the ends cartilaginous. B. Secondary center of ossification: – Appear in the ends of bones after birth forming the epiphysis which ossifies leaving: a. A plate of epiphyseal cartilage between the epiphysis and diaphysis. b. Articular cartilage covering the ends of the bone. N.B: The metaphysis is the more recently developed part of the bone added to the diaphysis adjacent to the epiphyseal plate. 19  According to structure (structural classification): Compact (hard or ivory) bones Spongy (trabecular or cancellous) bone – Hard and dense. – They look like a sponge which are – Form the surface layer of all bones and usually filled with red bone marrow. the tubular shafts of long bones – They are formed of spicules or (Diaphysis). trabeculae. – Consist of a number of cylindrical units – They are located inside the hard bone that form the Haversian system. and form the ends of long bones and the body of all other types of bone (Epiphysis). 20  Parts and structure of long bones: 1) Epiphysis: – The end of the long bone that formed of spongy bone. – covered by a thin layer of hyaline cartilage called articular cartilage. 2) The epiphyseal plate of cartilage: – Thin plate of cartilage. – Responsible for bone growth. – It ossifies at the age of 15 – 22 years. 3) Diaphysis (shaft): – Cylindrical mass of compact bone. – Enclosing a medullary cavity that contains the bone marrow. – It is surrounded by a fibrous membrane called periosteum. 4) Metaphysis: – Part of the shaft lying distal to the epiphyseal plate of cartilage. 5) Periosteum: – Thick layer of fibrous tissue. – Covers all bone surface except the articular cartilage. – Rich in blood supply and nerve supply. – Bundles of collagen fibers (sharpeys fibers) extend from the periosteum into the underlying bone. 21  Arterial blood supply of bones: 1. Epiphyseal arteries supplying the epiphysis. 2. Metaphyseal arteries supplying the metaphysis. 3. Nutrient artery: – Supplying the bone marrow of the shaft. – Enters the bone through nutrient canal. – Divides into proximal and distal branches. 4. Periosteal arteries: – The main source of blood supply. – Supplying the compact bone of the shaft. – Rising from a nearby main artery or from muscular arteries.  Nerve supply of bones: The bone itself is insensitive to pain but the periosteum is responsible for pain sensation. It is highly innervated by: 1. Sensory nerves derived from the periosteal nerves. 2. Vasomotor nerves, accompanying the blood vessels. Bone marrow – Occupies the marrow cavity. – At birth, the marrow of all bones is red. – With age, the red marrow is replaced by yellow marrow. – At the age of 7 years, yellow arrow begins to appear in the distal bones of the limbs. – In the adult, the red marrow is restricted to the bones of the skull, vertebral column, thoracic cage, girdle bones & head of humerus. 22  SKELETON ▪ It is the frame of the body. ▪ It is built of 206 bones: – 34 of them are single (unpaired). – 86 are paired.  Functions of the skeleton: 1. Provides the characteristic shape of the human body. 2. Supports the soft parts of the body. 3. Gives attachments for muscles and ligaments. 4. Acts as levers that help in muscle contractions. 5. Reservoir for calcium and phosphorus. 6. Production of red blood cells from the bone marrow. 7. Protects the important structures such as the brain, heart and lungs. Axial skeleton (80 Appendicular skeleton (126 bones) bones) Upper limbs (64 bones) Lower limbs (62 bones) Skull (28): Shoulder girdle (64 bones): Pelvic girdle (2 bones): – 8 = cranium. – 2 scapulae. – 2 hip bone. – 14 = face. – 2 clavicles. Thigh (2 bones): – 6 = auditory Ossicles. Arms (2 bones): – 1 femur in each thigh. – 1 humerus in each arm. Kneecap (2 bones): Hyoid bone (1 bone). Forearm (4 bone): – 1 patella in each cap. Vertebral Column (33 – 1 ulna in each forearm. Leg (4 bones): vertebrae / 26 bone): – 1readius in each – 1 tibia in each leg. – 7 cervical (separated). forearm. – 1 fibula in each leg. – 12 thoracic (separated) Wrist (16 bones): Ankle (14 bones): – 5 lumbar (separated) – 8 carpals in each wrist. – 7 tarsals in each Ankle. – 5 sacral (fused into 1 Hand (10 bones): Foot (10 bones): bone called sacrum). – 5 Metacarpal in each – 5 metatarsals in each – 4 coccygeal (fused into 1 hand. foot. bone called Coccyx). Fingers (28 bones): Toes (28 bones): – 14 phalanges in each – 14 phalanges in each Thoracic cage: 12 pairs (24) hand: foot: ribs. ✓ 2 in each thumb. ✓ 2 in each thumb. 1 sternum (3pieces). ✓ 3 in each finger. ✓ 3 in each toe. 23  SKULL Single bones Paired bones 1. Occipital bone: 1. Parietal bones: At the back of the skull. Forming the hind part of the roof of 2. Frontal bone: the skull. Forming the front part of the skull 2. Temporal bones: roof, the forehead and the upper At the sides, above the ears. parts of orbits. Cranium 3. Sphenoid bone: At the base of the cranium with wings on either side forming the temples. 4. Ethmoid bone: Between the frontal and the sphenoid, forming the roof of the nasal cavities. 1. Vomer: 1. Zygomatic (malar bones) in the Forming part of the nasal septum. cheeks. 2. Mandible: 2. Maxilla: Forming the lower jaw. Forming the upper jaw, most of the side walls of the nose and front part of the hard palate. Bones of face 3. Palatine bones: Forming the rest of the hard palate and part of the side walls of the nose. 4. Lacrimal bones: One in each eye socket or orbit. 5. Nasal bones: Form the bridge of the nose. 6. Inferior conchae: Inside the nose 24  External features of the skull: Superior Aspect:  It is the vault of the skull being formed of: – Frontal, 2 parietal and occipital bones. – Coronal, sagittal and lambdoid sutures. ▪ Coronal + sagittal suture = bregma. ▪ Sagittal + lambdoid suture = lambda. Inferior Aspect: ▪ It is the base of the skull and shows: – Hard palate which is formed from: a) The palatine bone posteriorly. b) The maxilla anteriorly. – Base of vomer (part of the nasal septum). – Bodies of the sphenoid & occipital bones. – Occipital condyles. – Styloid and mastoid processes. ▪ It also shows multiple foramina with the largest one called foramen magnum. Posterior Aspect: – Occipital bone. – Occipital protuberance. – Nuchal lines. 25  Anterior Aspect: – Frontal, nasal and maxillary bones. – The orbital cavity. – Anterior nasal aperture. Lateral Aspect: – The frontal, parietal, occipital, temporal & sphenoid bones and zygomatic arch. – Mastoid process. – External auditory meatus. Cranial cavity: – It is the base of the skull from inside. – Can be seen when the vault of the skull is removed. – It is divided into three big areas: a. Anterior cranial fossa. b. Middle cranial fossa. c. posterior cranial fossa. 26  Characters of the skull of newly born infant: Large in proportion to other parts of the skeleton with huge cranium and wide orbital openings. The bones are smooth, and their ossification is incomplete. Membranous areas are still unossified at the meeting of bones forming the fontanelles. 6 fontanelles are present in the fetal skull. The most important of which are Anterior & posterior fontanelles. Anterior fontanelle: – The larger of the two fontanelles. – Lies at the junction of the sagittal, coronal, and frontal sutures. – Diamond shaped measuring about 4 x 2.5 cm. – It is closed by the age of 18 months. Posterior fontanelle: – It is triangular. – Situated at the junction of the sagittal & Lambdoid sutures. – It is closed by the age of 6 months. ❖ Importance of the fontanelles: 1. Allow molding and overriding of the skull bones during labor. 2. Give space for the growth of brain & skull bones. 3. They are of importance in evaluating the baby’s growth and health as it helps in diagnosis of some disorders as dehydration and hydrocephalus. 27  MANDIBULE ▪ It is the bone which forms the lower jaw. ▪ It is formed of two parts: 1. Body: – Carries the lower set of teeth in their sockets. 2. Ramus: – It is wide, thin and directed upwards. – It forms the coronoid process anteriorly and the condyloid process posteriorly for articulation with the skull. VERTEBRAL COLUMN ▪ It is composed of 33 vertebrae. ▪ Some are fused, so that the real number is 26 bones. ▪ The vertebrae are connected by intervertebral discs. ❖ The vertebral column has the following regions: Cervical region in the neck 7 vertebrae. Thoracic or dorsal region 12 vertebrae. Lumbar region in the back 5 vertebrae. Sacral region in the pelvis 5 vertebrae fused into 1 sacrum. Coccygeal region 4 vertebrae fused into 1 coccyx. 28