THE BLOGGERS

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CHAPTER 7: Anatomy of Bones and Joints

Anatomy of Bones and Joints

         I. General Considerations in Bones

Osteology is the branch of medicine concerned with the development and diseases of   bone tissue. The human skeleton is composed of 270 bones in the newborn, 222 bones in children and 206 bones in adults.

The skeletal system may be divided into two functional parts:

• The axial skeleton consists of the bones of the head (cranium or skull), neck (hyoid bone and cervical vertebrae), and trunk (ribs, sternum, vertebrae, and sacrum).
• The appendicular skeleton consists of the bones of the limbs, including those forming the pectoral and pelvic girdles.

Out of the 206 bones an adult has, 126 of them exist in the appendicular skeleton, whereas 80 of them exist in the axial skeleton.

Bone is a living tissue capable of changing its structure as the result of the stresses to which it is subjected. Like other connective tissues, bone consists of cells, fibers, and matrix. It is one of the hardest structures of the animal body, because of the calcification of its extracellular matrix. Living bones have some elasticity (results from the organic matter) and great rigidity (results from their lamellous structures and tubes of inorganic calcium phosphate). Its color, in a fresh state, is pinkish-white externally, and deep red within.

II. Axial Skeleton

The axial skeleton consists of the 80 bones along the central axis of the human body. It is composed of six parts; the human skull, the ossicles of the middle ear, the hyoid bone of the throat, the rib cage, sternum and the vertebral column. The axial skeleton and the appendicular skeleton together form the complete skeleton.

Skull

The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.

The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates. The skull is a part of the skeleton.

Functions of the skull include protection of the brain, fixing the distance between the eyes to allow stereoscopic vision, and fixing the position of the ears to help the brain use auditory cues to judge direction and distance of sounds. In some animals, the skull also has a defensive function (e.g. horned ungulates); the frontal bone is where horns are mounted.

The English word "skull" is probably derived from Old Norse "skalli" meaning bald, while the word cranium comes from the Greek root kranion.

Different Views of the Skull

Superior View

Posterior View

Lateral View

Anterior View

Inferior View

                    Vertebral Column

                 The vertebral column forms the central part of the skeleton. It supports the skull and protects the spinal cord. It also serves as attachment for the ribs, the pectoral and pelvic girdles. The vertebral column consists of separate bones, the vertebrae. The different vertebrae are arranged above each other. Because the separate vertebrae are attached to each other by means of fibrous cartilaginous discs they form a flexible column. Each vertebra has articular surfaces above and below, which allow articulation movement between them.

                The vertebral column of 33 vertebrae is divided into five regions according to their position and structure. The five regions consist of: Seven cervical (neck) vertebrae, Twelve thoracic (chest) vertebrae, Five lumbar vertebrae, Five fused sacral vertebrae, and Four fused vertebrae.

        The Cervical Vertebrae

• The neck region consists of 7 cervical vertebrae. These are the smallest vertebrae in the vertebral column. The first two cervical vertebrae are known as the atlas and axis. They are specially adapted to support the skull and to enable it to move. They differ from the structure of the typical vertebra in certain respects.

       The Atlas

• The atlas is the first neck vertebra and supports the skull. It is ring-shaped and has no centrum. A neural spine is absent. The atlas consists of posterior and anterior neural arches and 2 short transverse processes. The spinal foramen (neural canal) is very large. The 2 occipital condyles of the skull fit into the articulating facets on the upper surface of the atlas, on either side of the neural canal. On its lower surface (inferior) surface the atlas has 2 articular surfaces for articulation with the axis.

         

          The Axis

• The axis has a large, strong neural spine. The centrum is small and has become modified to bear the odontoid process (a tooth-like projection) on its upper surface. The odontoid process fits against the facet in the anterior arch of the atlas. This forms a pivot joint or axis, around which the atlas (together with the skull) can rotate, so allowing the head to turn from side to side.

           The Thoracic Vertebrae

• There are 12 thoracic vertebrae. The centrum is large and sturdy and the neural spines are long and directed downwards. The long neural spines form an anchorage for the muscles and ligaments that support the head and neck. The head (or capitulum) of each of the first 10 pairs of ribs fits into and articulates with the semi-circular facet which is situated between two successive centra, i.e. between the inferior surface of one and the superior surface of the next centrum. These facets occur on both sides of the centrum. The tubercle of the rib articulates with the facet at the tip of the transverse process.

   

        The Lumbar Vertebrae

• These 5 vertebrae are the largest and strongest in the vertebral column. The transverse processes are very long for the attachment of the powerful back muscle that maintain the posture and flex the spine in movement.

          The Sacrum

• The sacrum is roughly triangular in shape and consists of 5 fused vertebrae. It lies between the hip bones, with which it articulates. Horizontal ridges indicate the divisions between the fused vertebrae. At the ends of these ridges are openings which allow nerves and blood vessels to pass through.

          The Coccyx

• The coccyx consists of 4 fused tail vertebrae which are small and have a relatively simple structure. They do not resemble the structure of a typical vertebra. The muscles of the buttocks are attached to the coccyx.

          The Ribs

• Twelve pairs of ribs articulate with the 12 vertebrae of the thoracic region. The ribs are flat, narrow bones with a distinctive bow-shaped curve. Each rib consists of a head or capitulum, a small tubercle (which is a short distance back from the head) and the shaft. The head of the rib articulates with the semi-circular articulating facets formed by the centra of two successive thoracic vertebrae. The tubercle fits into and articulates with the articulating facets on the transverse process. The first seven ribs on each side are joined to the breastbone by bars of hyaline cartilage (called costal cartilage in this region). The first seven pairs of ribs are referred to as true ribs. The cartilages of the 8th, 9th and 10th ribs are joined to the costal cartilage of the rib immediately above (i.e. to the costal cartilage of the 7th rib). These three pairs of ribs are known as vertebrochondral ribs. The last two pairs of ribs have free ends which are not attached to the sternum at all. They are floating ribs. The vertebrochondral ribs and the floating ribs are collectively known as false ribs. The ribs (together with their muscles) play an important role in the breathing mechanism of a mammal.

          The Sternum (Breastbone)

• The sternum is a long, flat, dagger-shaped bone. It is about 15 - 18 cm long and is found in the center of the chest region. The broad upper end supports the collar bones. The first seven pairs of ribs are attached to the articulating facets on the sides of the sternum. The 12 thoracic vertebrae, the 12 pair of ribs and the sternum forms the thorax which protects the delicate and vital organs of the thorax, viz. the heart and lungs.

               Thoracic Cage

            Thoracic Cage is made up of 24 bones arranged in 12 pairs. These bones are divided into three groups: true ribs, false ribs and floating ribs.

           The twelve pairs of ribs are often called the "rib cage." This is because they form a kind of cage that encloses the upper body. This cage gives the chest its familiar barrel-like shape.

           The ribs serve several important purposes. They protect the heart and lungs from injuries and shocks that might damage them. Ribs also protect parts of the stomach, spleen, and kidneys. The ribs help you to breathe. As you inhale, the muscles in between the ribs lift the rib cage up, allowing the lungs to expand. When you exhale, the rib cage moves down again, squeezing the air out of your lungs.

              III. Appendicular Skeleton
          The appendicular skeleton consists of the girdles and the skeleton of the limbs. The upper (anterior) limbs are attached to the pectoral (shoulder) girdle and the lower (posterior) limbs are attached to the pelvic (hip) girdle.

           The Pectoral Girdle

       The Pectoral girdle consists of two shoulder blades (scapulae) and two collar bones (clavicles). These bones articulate with one another, allowing some degree of movement.

          Shoulder Blades (Scapulae)

• The shoulder blade is a flat triangular bone which stretches from the shoulder to the vertebral column at the back. On the back side it has a bony ridge for the attachment of the muscles. The bony ridge forms a prominent projection, the acromion, above the shoulder joint. Beneath the collar bone and just on the inside of the shoulder joint, is another bony projection of the shoulder blade, the coracoid process, which also serves for the attachment of muscles. The upper outer corner of the shoulder blade ends in the glenoid cavity into which fits the head of the upper arm bone, forming a ball and socket joint.

         

         Collar Bones (Clavicles)

• Each collar bone is rod-shaped and roughly S-shaped. It lies horizontally and articulates with the upper end of the breastbone, right in the middle and front, just above the first rib. The lateral end articulates with the acromium. Collar bones serve as a support for the shoulder blades in front and keep the shoulder blades back so that the arms can hang freely at the sides of the body. They prevent the pectoral girdles from getting out of joint easily and ample movement of the shoulders.

               The Upper Limbs

               The skeleton of the upper limbs or arm may be divided into five main regions: an upper arm bone, the forearm (radius and ulna), the wrist, the palm of the hand and the fingers.

          The Upper Arm (Humerus)

• The upper arm is a single long bone. The upper end consists of a hemi-spherical ball which fits into the socket of the shoulder blade to form the shoulder joint. The lower end of the humerus forms a shallow ball and socket joint with the radius and a hinge joint with the ulna in the elbow.

          The Forearm (Radius and Ulna)

• The two long bones of the forearm are known as the radius and the ulna. The ulna is the larger of the two bones and is situated on the inner side (i.e. the little finger side) of the forearm. The upper end of the ulna articulates with the lower end of the humerus forming a strong hinge joint in the elbow region. The lower end of the ulna is slender and plays a minor role in the formation of the wrist joint. The radius is situated on the thumb side of the forearm. Its upper end articulates with both the humerus and the ulna. The broad, lower end of the radius forms a major part of the wrist joint, where it articulates with the wrist bones (carpals). The radius also allows the forearm to be rotated. The radio-ulnar joints are pivot joints in which the moving bone is the radius. As the head of the radius pivots at these joints, the lower end of the radius moves round the lower head of the ulna.

          The Wrist

• The wrist consists of eight carpal bones. These are small, short bones that are arranged in two rows of four. They have articulating facets which allow them to slide over one another.

          The Palm of the Hand

• The palm is supported by five long metacarpals. The metacarpals articulate with carpals at one end and with the phalanges at the other end.

          The Fingers

• The fingers are made up of fourteen phalanges. There are three phalanges in each finger but only two in the thumb.

                   The Pelvic Girdle

                 The pelvic girdle consists of two large, sturdy hip bones. Each hip bone consists of three fused bones namely the ilium, ischium and the pubis. The ilium is the largest of the three and forms the upper part of the hip bones. The sacrum fits like a wedge posteriorly between the two hip bones. The sacrum has a large, flat articular surface on each side for articulation with the ilia. The ischium forms the inferior part of the hip bone and the pubis the central in front. The two pubic bones are attached in the middle, on the front side by a symphysis which consists of fibrocartilage and ligaments, the pubic symphysis. The two hip bones and the sacrum form a complete bony ring, the pelvis . On the outer side of the point where the fused bones meet, there is a deep hip socket into which the head of the femur fits.

             The pelvic girdle forms a strong support for the attachment of the limbs. Strong muscles of the back, the legs and the buttocks are attached to it. It protects some of the internal organs. In females it forms a strong basin-like structure for supporting and protecting the developing fetus during child-bearing.

     

                  The Lower Limbs

                The skeleton of the lower limb may be divided into five main regions: the upper leg (thigh), the lower leg, the ankle, the arch of the foot and the toes.

          The Upper Leg or Thigh

• The upper leg has a single long bone, the femur and is the longest bone in the body. The head of the femur is turned slightly inwards and has a large, rounded portion which articulates in the acetubulum, forming a ball-and-socket joint. At its distal end, the femur widens to form two large knobs (condyles) which form the hinged knee joint with the main long bone (tibia) of the lower leg. On the anterior side of these two condyles, there is an articular surface against which the kneecap (patella) slides. The patella is a small, triangular, flat bone which develops on the tendon of the thigh muscle and is attached by ligaments to the tibia. This enables movement in the knee joint.

         The Lower Leg

• The two bones of the lower leg are the tibia (shinbone) in front and the fibula behind. The tibia is the larger of the two and extends from the knee to the ankle. The upper end of the tibia has two articulating facets into which the condyles of the femur fit to form the knee joint. The lower end of the tibia articulates with one of the tarsals to form the ankle joint. The fibula is smaller than the tibia and is situated on the outside and slightly behind it. The upper end articulates with the tibia but does not form part of the knee joint. The lower end forms part of the ankle joint.

          The Ankle

• There are seven short, thick tarsal bones, the largest of which is the heel bone (calcaneum), which presses firmly onto the ground when one stands, walks or runs. The calf muscles are attached to the calcenum, allowing the heel to be lifted during locomotion.

          The Arch of the Foot

• The arch is formed partly by some of the tarsals but mainly by the five long metatarsals, which extends from the tarsals to the toes. The arch is modified for receiving the weight of the body.

          The Toes

• There are fourteen short phalanges in the toes of each foot. The big toe has two phalanges and the other toes have three in each.

CHAPTER 6: Histology and Physiology of Bones

CARTILAGE: What I have learned?

Cartilage is a flexible connective tissue that is present in our body. It  has a lot of benefits, such as,  it provides  support, provides  a framework in which deposits of bones and can be equipped with smooth surfaces available to monitor the movement of articulation of the bones. There are three different types of cartilage:

Hyaline Cartilage, also called gristle. It is shiny, slippery, firm, translucent, and bluish-gray in color. It is simple in structure, with no nerves or blood vessels. It has high elasticity and helps cushion and protect bones. The word hyaline comes from the Greek for glassy, and refers to the translucence of the tissue. 

Fibrocartilage, A tough cartilage with a matrix consisting of dense bundles of fibers. Intervertebral discs and menisci are made of fibrocartilage, which has great tensile strength and is able to absorb considerable loads.

Elastic cartilage has a preponderance of dark-staining elastic fibers embedded in ground substance.  These fibers are clearly visible and this trait is the single, best identifier to be used for differentiating elastic cartilage from hyaline.  Perichondreum is also typically found around elastic cartilage.  Elastic cartilage is found in the pharyngotympanic(eusatachian) tubes, epiglottis, and ear lobes where needs dictate supportive tissues possess elasticity.artilage

BONES: What does it mean to me????? 

In this Chapter, I also learned the components of the skeletal system. 

BONE is the basic unit of the human skeletal system and provides the framework for and bears the weight Of the body, protects the vital organs, supports mechanical movement, and maintains iron homeostasis.

Classification of Bone

Bones can be classified based on their position, shape, size, and structure.

Based on location, bones can be classified as follows:

• Axial skeleton – Bones of the skull, vertebral column, sternum, and ribs

• Appendicular skeleton – Bones of the pectoral girdle, pelvis girdle, and limbs

o Acral skeleton – Part of the appendicular skeleton, including bones of the hands and feet

Based on shape, bones can be classified as follows:

• Flat bone – Bones of the skull, sternum, pelvis, and ribs

• Tubular bone –

o Long tubular bone, including bones of the limbs

o Short tubular bone, including bones of the hands and feet, such as the phalanges, metacarpals, and metatarsals

• Irregular bone – Bones of the face and vertebral column

• Sesamoid bone – Bones that develop in specific tendons, the largest example of which is the patella

• Accessory bone or supernumerary bone - Extra bones that develop in additional ossification centers or bones that failed to fuse with the main parts during development(Accessory bones are common in the foot and may be mistaken for bone chips or fractures.)

Based on size, bones can be classified as follows:

• Long bone – Tubular in shape, with a hollow shaft and 2 ends, including bones of the limbs

• Short bone – Cuboidal in shape, located only in the foot (tarsal bones) and wrist (carpal bones)

Gross Structures of Bone was also discussed here.

The gross structure of a long bone can be divided into several regions.

Epiphysis

In the long bones, the epiphysis is the region between the growth plate or growth plate scar and the expanded end of bone, covered by articular cartilage. An epiphysis in a skeletally mature person consists of abundant trabecular bone and a thin shell of cortical bone (see the image below). Although an epiphysis is present at each end of the long limb bones, it is found at only one end of the metacarpals (proximal first and distal second through the fifth metacarpals), metatarsals (proximal first and distal second through fifth metatarsals), phalanges (proximal ends), clavicles, and ribs.

Cortical bone is composed of haversian systems (osteons). Each osteon has a central haversian canal and peripheral concentric layers of lamellae.

The epiphysis is the location of secondary ossification centers during development. The structure of the epiphysis is more complex in bones that are fused from more than one part during development. Examples include the proximal and distal ends of the humerus, femur, and vertebrae. For instance, the proximal end of the humerus is developed from 3 separate ossification centers, which later coalesce to form a single epiphyseal mass. In the proximal humeral epiphysis, one of the centers forms the articular surface, and the other 2 become the greater and lesser tuberosities. Carpal bones, tarsal bones, and the patella are also called epiphysioid bones and are developmentally equivalent to the epiphyses of the long bones.

Knowledge of the location of the epiphysis and its equivalents in various bones aids clinicians in the recognition of the origin of bone lesions and further facilitates the diagnostic considerations, as some bone tumors such as chondroblastoma have a strong predilection for the epiphysis or epiphysioid bones.

Metaphysis

The metaphysis is the junctional region between the growth plate (see the image below) and the diaphysis. The metaphysis contains abundant trabecular bone, but the cortical bone thins here relative to the diaphysis. This region is a common site for many primary bone tumors and similar lesions. The relative predilection of osteosarcoma for the metaphyseal region of long bones in children has been attributed to the rapid bone turnover due to extensive bone remodeling during growth spurts (see Growth, Modeling, and Remodeling of Bone, below).

 Growth plate.

Osteosarcoma is a malignant primary bone tumor that is characterized by neoplastic osteoblasts that produce osteoid. Because of increased osteoblastic activity, the serum level of alkaline phosphatase is often significantly increased in this disease; however, acid phosphatase is synthesized by osteoclasts and will not be significantly increased in this disease, although scattered osteoclasts can also be present. The Codman triangle is a pattern of periosteal reaction that is often associated with osteosarcoma, although this pattern may also be seen with other aggressive processes, including osteomyelitis.

Diaphysis

The diaphysis is the shaft of long bones and is located in the region between metaphyses, composed mainly of compact cortical bone. The medullary canal contains marrow and a small amount of trabecular bone.

Physis (epiphyseal plate, growth plate)

The physis is the region that separates the epiphysis from the metaphysis. It is the zone of endochondral ossification in an actively growing bone or the epiphyseal scar in a fully grown bone.

WHAT ARE THE CELLS FOUND IN OUR BONE???

The cells found in the bone are the OSTEOBLAST, OSTEOCYTES and OSTEOCLAST.

osteblast- Osteoblasts are also responsible for mineralization of this matrix. Zinc, copper and sodium are some of the minerals required in this process. Bone is a dynamic tissue that is constantly being reshaped by osteoblasts, in charge of production of matrix and mineral, and osteoclasts, which remodel the tissue. Osteoblast cells tend to decrease with age, affecting the balance of formation and resorption in the bone tissue. 

OSTEOCYTES-it is the most abundant cell found in compact bone.  It is responsible for the breakdown of bones.

   

OSTEOCLAST- is a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone (organic dry weight is 90% collagen).

WHAT IS CANCELLOUS AND COMPACT BONE?

Cancellous bone- is the meshwork of spongy tissue (trabeculae) of mature adult bone typically found at the core of vertebral bones in the spine and the ends of the long bones (such as the femur or thigh bone).

Compact Bone- is what is found on the outside of bones. It is the hard outer layer that gives bones their smooth white appearance.

 

WHAT IS THE CENTER OF OSSIFICATION

the center of ossification is the site where bone begins to form in a specific bone or part of bone as a result of the accumulation of osteoblasts in the connective tissue. It is where bone begins to form in the shaft of a long bone or the body of an irregular bone; primary ossification center. Bone formation continues after beginning in the long shaft or body of the bone, usually in an epiphysis; secondary ossification center.

What is FONTANELS???

It is one of the membrane-covered spaces remaining at the junction of the sutures in the incompletely ossified skull of the fetus or infant. Actually there are two soft spots close together, representing gaps in the bone structure which will be filled in by bone during the normal process of growth. The anterior fontanelle is diamond shaped and lies at the junction of the frontal and parietal bones. This fontanelle usually fills in and closes between the eighth and fifteenth months of life. The posterior fontanelle lies at the junction of the occipital and parietal bones, is triangular in shape, and usually closes by the third or fourth month of life. Though these “soft spots” may appear very vulnerable, they may be touched gently without harm. Care should be exercised that they be protected from strong pressure or direct injury.

BONE GROWTH: unlike cartilage, bones cannot grow by interstitial growth. Bones increase in size only by APPOSITIONAL GROWTH, the formation of new bone on the surface of older bone or cartilage.

watch this:

BONE REPAIR

bone is a living tissue that can undergo repair following damage to it.

THE IMPORTANCE OF CALCIUM IN OUR BONES

Calcium as most of us know is an important part of our bones. Calcium gives our bones the necessary strength to carry our body weight. Calcium is also required for functioning of all the muscles and the most important muscle being the heart of course. Without calcium, muscles would not contract normally, blood would not clot and nerves would be unable to carry messages. Calcium and bone health go hand-in-hand. Increasing scientific evidence indicates that adequate calcium intake reduces the risk of several major chronic diseases, most notably osteoporosis, a potentially crippling disease of thin and fragile bones. Calcium also helps protect against colon cancer, high blood pressure and recurring premenstrual syndrome, and possibly cardiovascular disease and kidney stones (well most think it causes stones)

CHAPTER 5- Integumentary System

The Integumentary System
Integumentary System: What I have learned?

The integument as an organ: The integumentary system includes the skin and the skin derivatives hair, nails, and glands. The integument is the body’s largest organ and accounts for 15% of body weight. It is an organ that is involved in protection and barrier function.

The derivatives of the integument:
Hair: functions include protection & sensing light touch.
Hair is composed of columns of dead, keratinized cells bound together by extracellular proteins. Hair has two main sections: The shaft- superficial portion that extends out of the skin and the root- portion that penetrates into the dermis. Surrounding the root of the hair is the hair follicle. At the base of the hair follicle is an onion-shaped structure called the bulb Papilla of the hair and the matrix within the bulb produce new hair.

Nails: participate in the grasp & handling of small things.
Nails are plates of tightly packed, hard, keratinized epidermal cells.


 

The nail consists of:
nail root: -the portion of the nail under the skin,
nail body: -the visible pink portion of the nail, the white crescent at the base of the nail is the lunula, the hyponychium secures the nail to the finger, the cuticle or eponychium is a narrow band around the proximal edge of the nail and
free edge: -the white end that may extend past the finger.
Glands: participate in regulating body temperature.
There are three main types of glands associated with the integument:


Sebaceous - Oil glands. Located in the dermis, and secrete sebum.
Sudoriferous - Sweat glands. Divided into two main types:
Eccrine - Most common, main function is regulation of body temperature by evaporation, and
Apocrine - Responsible for “cold sweat” associated with stress.
Ceruminous – Lie in subcutaneous tissue below the dermis, secrete cerumen (ear wax) into ear canal or sebaceous glands.
The Two Layers of Skin:

Epidermis – The Epidermis is the thinner more superficial layer of the skin.
The epidermis is made up of 4 cell types:
(A) Keratinocytes – Produce keratin protein a fibrous protein that helps protect the epidermis
(B) Melanocytes - produces the brown pigment melanin
(C) Langerhan Cells – participate in immune response and
(D) Merkel cells - participates in the sense of touch.
There are five distinct sub-layers of the Epidermis:

Stratum corneum: the outermost layer, made of 25-30 layers of dead flat keratinocytes. Lamellar granules provide water repellent action and are continuously shed & replaced.
Stratum lucidum: Only found in the fingertips, palms of hands, & soles of feet. This layer is made up of 3-5 layers of flat dead keratinocytes.
Stratum granulosum: made up of 3-5 layers of keratinocytes, site of keratin formation, keratohyalin gives the granular appearance.
Stratum spinosum: appears covered in thornlike spikes, provide strength & flexibility to the skin.
Stratum basale: The deepest layer, made up of a single layer of cuboidal or columnar cells. Cells produced here are constantly divide & move up to apical surface.
Dermis: is the deeper, thicker layer composed of connective tissue, blood vessels, nerves, glands and hair follicles.
The epidermis contains 3 cell types:
Adipocytes,
Macrophages and
Fibroblasts.
There are two main divisions of the dermal layer:
Papillary region - The superficial layer of the dermis, made up of loose areolar connective tissue with elastic  fibers.
Dermal papillae - Fingerlike structures invade the epidermis, contain capillaries or Meissner corpuscles which respond to touch.
Reticular region of the Dermis – Made up of dense irregular connective & adipose tissue, contains sweat lands, sebaceous (oil) glands, & blood vessels.




Hypodermis: the hypodermis is not a skin layer but lies below the dermis, and is a subcutaneous tissue which contains fat, blood vessels and sensory receptors.










“CROSS SECTION OF THE SKIN”

Clinical Considerations
Cleavage lines Cleavage lines are the tension lines in skin which follow the direction of the arrangement of collagen bundles in the dermis. Incisions along theses lines heal faster and give minimum scarring.
Burns Burns are classified according to how deep the burn has penetrated, as well as the percentage of surface area affected.
Depth;
Burns can be classified as partial or full thickness burns, first, second or third degree burns.
Partial thickness
First degree burns The burn has penetrated the epidermis only. Red and painful, only slight swelling.
Second degree burn The burn has penetrated the epidermis and the dermis. Red and painful, swelling and blistering.
Full-thickness
Third degree burn The burn has destroyed the epidermis and dermis and penetrated the hypodermis. Painless, the colour can be white, tan, brown black or red.
Surface area;;
In adults the Wallace's 'Rule of Nines' is used to work out an approximate percentage of total skin surface area that has been affected by the burn. Each area is approximately divided into multiples of 9. In infants and children (under 15) the body proportions are different and so this rule is not the same.
Body area Surface area
Head 9%
Upper limb (single) 9%
Trunk (front or back) 18%
Genitals 1%
Lower Limb (single) 18%


Skin absorption The epidermis is able to absorb lipid soluble substances and therefore certain medications can be applied to the surface of the skin.


Skin Function
Skin has several important functions;
Skin Function
Protects our bodies from trauma.
Wound healing.
Acts as a barrier to bacteria and viruses.
Produces vitamin D, essential for growth and bone maintenance.
Prevents us absorbing and losing excess water.
Secretes waste products.
Regulates our body temperature (thermoreceptors, sweat, vasodilation).
Sense what is happening in our external environment (touch, pressure, heat).
Pigments as well as hair on our heads protect us from the sun.
Secretes sebum.
Advertises sexual maturity.
Disperses scents.
Clinical Considerations
Wound healing It is important for the skin to repair quickly to prevent infection. If the epidermis is damaged it will simply heal by regrowing to cover the damaged area. If the damage reaches into the dermis and cuts the vessels, the blood will form a blood clot and healing of the wound will begin.
Phases of Wound Healing Processes of wound healing
Inflammatory Response Blood clotting occurs. White blood cells are brought to the wound site.
Migratory Phase Epithelial and fibroblast cells migrate beneath the clot and the blood vessels regenerate (angiogenesis).
Proliferation Phase Epithelial cells proliferate (epithelialisation) beneath the scab and the fibroblasts produce collagen and the wound is pulled together.
Maturation Phase Collagen fibres become more organized, pulling the wound together.

CHAPTER 4: Tissues, Glands, and Membranes

TISSUES, GLANDS, and MEMBRANES

As a beginner student in the field of medicine, honestly saying I don’t have any idea that there are different types of cells, glands and membranes which are part of the composition of our human body. But as time goes by, as the time I’ve reached the age of 12 I think, I’ve some ideas about human body compositions. And as I become a first year nursing student of SLCN. I’ve discover all of these ideas which I will share here our blog. I hope that I could share my knowledge to everyone who might have the chance to read this blog of ours. These are the things that I’ve learned in the 2^nd semester in Human Anatomy and Physiology. How I wish I could be our professor in HAP, he is really amazing. If you will have the chance to know him, I know you’ll surely agree with me. Look what we’ve learned from him. So let’s start I hope you’ll enjoy reading these blog, there are some pictures and videos shown. Sorry if there are some grammars that are wrong, I’m that good in English. Then enjoy, and thanks for visiting our blog! Looking forward for your good comments.

  

Embryonic Tissue:

From the term itself, an embryonic tissue is the tissue that can be found in an embryo. Endoderm and Ectoderm are the cells that give rise to a new individual. The cells of ectoderm will migrate between the two layers and the so called mesoderm will be formed. Endoderm is the inner layer; Ectoderm is the outer layer and Mesoderm is the middle layer. They are called the germ layers; it is because they give rise to all the body tissues. There is a portion of the ectoderm called Neuroectoderm (Nervous System). 

The Four known types of Tissues are:
1. Epithelial Tissue
2. Connective Tissue
3. Muscle Tissue
4. Nervous Tissue

1.   Epithelial Tissue a layer of cells that serves as a protective covering over some surface, such as the outside of an organ or the lining of the wall of a cavity in the body. Epithelial cells generally have large nuclei, clear outlines, and a large amount of granular protoplasm. Some, called columnar, are long and narrow and may, as in the respiratory tract, have hairlike cilia extending from the outer surface. The skin contains several layers of epithelial cells, with columnar cells at the bottom, squamous cells at the top, and cuboidal cells in middle layers. Many of the secretory glands are composed of epithelial cells as are some of the endocrine glands.

Functions of Epithelial Tissues:

1. Protecting underlying structures.
2. Acting as barriers.
3. Permitting the passage of substances.
4. Secreting substances.
5. Absorbing substances

Structural Classifications of Epithelial Tissue:

Simple Squamous
Structure: Single layer or flat, often hexagonal cells.
Function: Diffusion, filtration and etc.
Common Location: Lung alveoli

Simple Cuboidal
Structure: Single layer of cube-shaped cells.
Fuction: Active transport and it facilitates diffusion.
Common Location: Kidney Tubules

Simple Columnar
Structure: Single layer of tall, narrow cells.
Function: Movement of particles out of the bronchioles of the lungs.
Common Location: Lining stomach and Intestines 

Pseudostratified
Structure: Single layer of cells, Some are tall and thin.
Function: Synthesize and secretes mucus membrane.
Common Location: Trachea and Bronchus

Stratified Squamous
Structure: Multiple layers of cells that are cuboidal in basal layer.
Function: Protection against abrasion and barrier from infections.
Common Location: Skin, Mouth and Esophagus

Stratified Cuboidal
Structure: Multiple layers of cube-shaped cells.
Function: Absorption and protection against microorganisms.
Common Location: Parotid gland duct

Stratified Columnar
Structure: Multiple layers of cells with tall and thin cells.
Function: Protection and secretion.
Common Location: Larynx

Transitional

Structure: Stratified cells that appear cuboidal when a certain organ isn't stretched.

Function: Accommodates fluctuations.

Common Location: Ureter, Urethra and Urinary bladder

2.    Connective Tissue which support and hold parts of the body together, comprise the fibrous and elastic connective tissues, the adipose (fatty) tissues, and cartilage and bone. In contrast to epithelium, the cells of these tissues are widely separated from one another, with a large amount of intercellular substance between them. The cells of fibrous tissue, found throughout the body, connect to one another by an irregular network of strands, forming a soft, cushiony layer that also supports blood vessels, nerves, and other organs. Adipose tissue has a similar function, except that its fibroblasts also contain and store fat. Elastic tissue, found in ligaments, the trachea, and the arterial walls, stretches and contracts again with each pulse beat. In the human embryo, the fibroblast cells that originally secreted collagen for the formation of fibrous tissue later change to secrete a different form of protein called chondrion, for the formation of cartilage; some cartilage later becomes calcified by the action of osteoblasts to form bones. Blood and lymph are also often considered connective tissues.

Functions of a Connective Tissue:

1.   Enclosing and separating.

2.   Connecting

3.   Supporting and moving

4.   Storing

5.   Cushioning and insulating

6.   Transporting
7.  Protecting

Structural classification of Connective Tissue

Loose Connective
Structure: Fine network of fibers.
Function: Loose packing support and nourishment.
Common Location: Skin

Dense Regular Collagenous
Structure: Matrix compose of collagen fibers
Function: Great tensile strength and stretch resistance
Common Location: Ligament and Tendon

Dense Regular Elastic
Structure: Regularly arranged collagen fibers and elastin fibers.
Function: Stretching and recoiling
Common Location: Tongue and Vestibular fold

Dense Irregular Collagenous
Structure: Alternating planes of fibers.
Function: Tensile Strength
Common Location: Skin

Dense Irregular Elastic
Structure: Bundles of sheets and elastin fibers
Function: Strength and stretching
Common Location: Aorta

Adipose
Structure: Full of lipid
Function: Packing material, thermal insulator, etc.
Common Location: Mammary gland

Reticular
Structure: Fine network of reticular fibers
Function: Provides a superstructure for lymphatic and hemopoietic .
Common Location: Lymph Node and Spleen

Hyaline Cartilage
Structure: Small and evenly dispersed.
Function: Allows growth, provides rigidity.
Common Location: Bone

Fibrocartilage
Structure: Thick bundles
Function: Flexible and capable of withstanding pressure.
Common Location: Intervertebral disk

Elastic Cartilage
Structure:Matrix contains elastic fibers.
Function: Provides rigidity and flexibility.
Common Location: Ears

Bone
Structure: Hard, bony matrix predominates.
Function: Provides strength, support and protects.
Common Location: Bones

Blood
Structure: Blood cells and a fluid matrix
Function: Transports oxygen etc.
Common Location: Red and white blood cells

3.    Muscle Tissue these tissues, which contract and relax, comprise the striated, smooth, and cardiac muscles. Striated muscles, also called skeletal or voluntary muscles, include those that are activated by the somatic, or voluntary, nervous system. They are joined together without cell walls and have several nuclei. The smooth, or involuntary muscles, which are activated by the autonomic nervous system, are found in the internal organs and consist of simple sheets of cells. Cardiac muscles, which have characteristics of both striated and smooth muscles, are joined together in a vast network of interlacing cells and muscle sheaths.

Structural Classification of Muscle Tissue  

Skeletal Muscle

    This type of muscle is composed of long fibers surrounded by a membranous sheath, the sarcolemma. The fibers are elongated, sausage-shaped cells containing many nuclei and clearly display longitudinal and cross striations. Skeletal muscle is supplied with nerves from the central nervous system, and because it is partly under conscious control, it is also called voluntary muscle. Most skeletal muscle is attached to portions of the skeleton by connective-tissue attachments called tendons. Contractions of skeletal muscle serve to move the various bones and cartilages of the skeleton.

b.    Smooth Muscle

                               

Smooth Muscle

Visceral, or involuntary, muscle is composed of spindle-shaped cells, each having a central nucleus. The cells have no cross striations, although they do exhibit faint longitudinal striations. Stimuli for the contractions of smooth muscles are mediated by the autonomic nervous system. Smooth muscle is found in the skin, internal organs, reproductive system, major blood vessels, and excretory system.

c.     Cardiac Muscle

Cardiac Muscle

This muscle tissue composes most of the vertebrate heart. The cells, which show both longitudinal and imperfect cross striations, differ from skeletal muscle primarily in having centrally placed nuclei and in the branching and interconnecting of fibers. Cardiac muscle is not under voluntary control. It is supplied with nerves from the autonomic nervous system, but autonomic impulses merely speed or slow its action and are not responsible for the continuous rhythmic contraction characteristic of living cardiac muscle.

4.    Nervous Tissue these highly complex groups of cells, called ganglia, transfer information from one part of the body to another. Each neuron, or nerve cell, consists of a cell body with branching dendrites and one long fiber, or axon. The dendrites connect one neuron to another; the axon transmits impulses to an organ or collects impulses from a sensory organ.

Nerve cell
 Axon- is the transmitter. Dendrites - is the receiver.

      GLANDS
          

              Gland - a gland is a secretory structure. There are two types of glands first is the endocrine glans which do not consist ducts and exocrine glands. Endocrine glands is the one responsible for secreting hormones, which enter the blood and are carried to other parts of the body. Exocrine glands, release their secretion into ducts which empty onto a surface or a cavity. Exocrine glands can also be classified according to how it products leave cell. Merocrine glands, are glands of the cell that produce secretions by active transport or produce vesicles that contain secretory products. Apocrine glands, it is the secretory products that are stored in the cell near the lumen of the duct. and the Holocrine gland it is the secretory products are stored in the cells of the gland.

Glands

          

        MEMBRANE

      Membrane - is a thin sheet or layer of tissue that covers a structure or lines a cavity. Most membranes are formed from epithelium and the connective tissue on which it rests.There are three major categories of internal membranes are mucous membranes, serous membranes and synovial membranes. Mucous membranes, consist of various kinds of epithelium resting on a thick layer of loose connective tissue. Serous membranes, consists of simple squamous epithelium resting on a delicate layer of loose  connective tissue. It doesn't contain glands but it do produces serous fluid. And Synovial membranes, consists of modified connective tissue of the joint cells, either intermixed with part of the dense connective tissue of the joint capsule. It produces synovial fluid, which lubricates the joint for smooth joint movement.

      So these are all the things I've learned as we start our lesson in Human Anatomy and Physiology. 

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