Skin and Fascia
Q. Enumerate the :
- functions of skin
- layers of skin
- appendages of skin
A. a. Functions of skin:
- Protection: Protect the body from mechanical injury and pathogens.
- Thermoregulation : Helps in maintaining normal body temperature .
- In summers the excess heat is lost from the body by
- secretion and evaporation of sweat from sweat glands,
- radition from the dilated blood vessels.
- In winters heat is conserved due to the presence of the subcutaneous fat and hair.
- In summers the excess heat is lost from the body by
- Prevents loss of body fluids.
- Acts as a sense organ:Is provided with various types of sensory endings for the perception of sensations such as pain, touch, heat & cold.
- Syntesizes Vitamin D.
b. Layers of skin:
- is the superficial layer.
- It is made up of keratinized stratified squamous epithelium, therefore like all epithelia , it is avascular.
- Layers of epidermis :
- Stratum germinativum
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
Stratum lucidum is found only in thick skin i.e. in sole and palm.
- It is the deeper layer.
- The dermis is composed of two layer – papillary layer (superficial layer) and reticular layer (deeper layer).
- Papillary layer- consists of loose connective tissue containing elastic, reticular, collagen fibers and capillaries ( help in nourishing epidermis). It form projections called dermal papillae, which fit into reciprocal depressions of epidermis.
- Reticular layer – consists of dense irregular connective tissue containing larger blood vessels,nerve endings, lymphatics, and epidermal appendages, elastic and collagen fibers that are arranged in layers parallel to the surface. Direction of the collagen fibers produces clevage/Langer lines.
c. Appendages of skin:
- Sweat gland
- Sebaceous gland
- Langer’s lines
A. 1. Langer’s lines or clevage lines are the lines on the surface of skin which are caused due to the orientation of collagen fibers in the dermis. They run longitudinally in the limbs and circumferentially in the neck and trunk. Incisions made along or parallel to the Langer’s lines will severe fewer fibers as a result the healing is faster and the scar formation is minimal.
2. Dermatome: The area of skin supplied by a single segment of spinal nerve is called a dermatome. Knowledge of dermatomes is essential to carry out neurological examination. Touching (using a cotton) skin in a particular dermatome in conscious patient can be used to localize injury to a specific spinal nerve or specific spinal segment.
Q. Enumerate the pigments that contribute to the colour of skin.
A. The colour of skin is due to the presence of the:
- Melanin – black brown pigment produced by melanocytes ( all humans have almost same number of melanocytes, but the amont of melanin synthesized is different in different races, which determines the colour of the skin of individuals.
- Carotene – yellow – orange pigment which is taken up from the vegetables (such as carrot).
- Hemoglobin – present in blood is responsible for pink colour.
Q. Enumerate the:
- Areas devoid of sebaceous glands
- Areas with abundant sebaceous glands
A. 1. Areas devoid of sebaceous glands:
- Skin of Palm and Sole
2. Areas with abundant sebaceous glands:
Q. How the degree of burns is calculated in extensive burns?
A. It is assessed by calculating the percentage of the skin covering the area that is affected. This follows the ‘rule of nine’ and is expressed as follows.
- Head & neck 9%
- Each upper limb 9%
- Front of the trunk 18%
- Back of the trunk 18%
- Each lower limb 18%
- Perineum 1%
Q. How are skin burns classified?
A. The skin burns are classified as :
- First degree: Only epidermis is involved and and heals in 3-5 days.
- Second degree : Involves epidermis and superficial part of dermis. Heals within few weeks.
- Third degree: Both epidermis and dermis are burnt. Requires skin grafting as regeneration is not possible. the hair follicles, sebaceous and sweat glands are destroyed which are the sites where regeneration begins.
Q. Write anatomical basis of:
- Incisions are preferably made parallel to cleavage/Langer’s lines.
A. Albinism: is a congenital disorder characterized by the complete or partial absence of melanin in the skin, hair and eyelashes. It is a autosomal recessive/X -linked disorder. Although the melanocytes are present, but genetic mutation results in lack of tyrosinase enzyme, which catalyses the production of melanin from tyrosine.
Vitilogo : is a clinical condition with presence of spots without melanin in the skin, which occurs due to partial or complete absence of melanocytes.
Incisions are preferably made parallel to cleavage/Langer’s lines: The reticular layer of dermis of skin contains bundles of collagen fibers which run in parallel rows. The direction of bundles of collagen fibers are responsible for cleavage/Langer’s line which run longitudinally in the limbs and circumferentially in the neck and trunk. Incisions made parallel to cleave lines will cut fewer collagen fibers. As a result the wound heals faster and does not lead to formation of ugly scar.
Q. Describe briefly:
- Superficial fascia and its contents.
- Functions of superficial fascia.
- Deep fascia and its modifications.
- Bursa and write its functional significance.
A. 1. Superficial fascia is the subcutaneous layer of loose connective tissue that connects the skin to the underlying deep fascia. Its contents are:
- Superficial blood vessels
- Cutaneous nerves
- Superficial lymphatics
- Mammary gland in females
- Remnants of panniculus carnosus ( muscle in superficial fascia) e.g. platysma in neck, muscles of scalp and muscles of facial expression.
2. Functions of superficial fascia
- It provides passage to blood vessels, verves and lymphatics.
- Acts as cushion and provide insulation ( due to presence of fat).
- Allows mobility of skin over underlying structures.
3. Deep fascia is a dense , inelastic fibrous layer that lies deep to superficial fascia and covers the deeper structures such as bones, muscles nerves and blood vessels.It becomes continuous with the outermost covering layer of underlying structures i.e. periosteum, perimysium, perineurium, and adventitial layer of blood vessels.
Modifications of deep fascia are :
- Intermuscular septa: In limbs the deep fascia send septa from its deep surface to the bone which separate the muscles into different compartments. They between the groups of muscles.
- Retinaculum : Are present where tendons cross the joint. Flexor and extensor retinacula are present around the wrist and ankle joint.
- Fibrous flexor sheath: Thickened deep fascia of fingers and toes on the flexor surface. It retains the fexor tendons close to the joints and prevent their bow stringing.
- Aponeuroses: Deep fascia of palm and sole are thickened to form palmar and plantar aponeuroses respectively. They protect the underlying structures.
- Ligament: Thickenings of deep fascia which connect bones at joints. They hold ends of the bones close to each other during movements and thus provide stability to the joints.
- Interosseous membrane: Are present beteen the raius and ulna bones of forearm and tibia and fibula in the leg.
- Fibrous capsules: Deep fascia splits to enclose certain glands ( such as parotid, thyroid) to form their capsule.
- Plantar and palmar aponeurosis : Thickening of deep fascia in sole and palm to protect underlying blood vessels and nerves.
Sites where deep fascia is absent : Face and anterior abdominal wall
3. Bursa is a closed serous sac lined by a serous membrane. They are found between the structures that move relative to each other in close apposition e.g. subcutaneous, subtendinous, subcapsular, intertndinous etc. They reduces friction and allow free movement between the apposed surfaces. Infection of bursa is called bursitis.
|Adventitious bursae : Bursae that are not normally present but develop over bony surfaces which are subjected to frequent friction and pressure e.g.:
a. Tailor’s ankle: Appears In tailors above the lateral malleolus
b. Porter’s shoulder : in porters, between upper surface of clavicle and skin
c. Weaver’s bottom: between gluteus maximus and ischial tuberosity.