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# Glandular Tissue & Lymphatic System ## Chapter 7: Glandular Tissue ### Summary This chapter details the endocrine and exocrine glands of the head and neck, their locations, secretions, functions, innervations, lymphatic drainage, and blood supply. Understanding these glands is crucial for dental professionals to identify disease processes. ### Key Information #### Gland Types - **Exocrine Gland:** Has a duct to empty secretions directly to the site of use (e.g., salivary glands). - **Endocrine Gland:** Ductless, secretes directly into the vascular system (e.g., thyroid gland). - Motor nerves regulate secretion flow; sensory nerves are also present. #### Lacrimal Glands - **Type:** Paired almond-shaped exocrine glands. - **Secretions:** Lacrimal fluid (tears) for lubricating the conjunctiva and eyeball. - **Location:** Lacrimal fossa of the frontal bone, just inside the lateral part of the supraorbital rim. - **Ducts:** Lacrimal ducts collect tears, which then pass to the lacrimal punctum, lacrimal sac, nasolacrimal duct, and finally drain into the inferior nasal meatus. - **Innervation:** Parasympathetic fibers from the greater petrosal nerve (branch of facial nerve), synapsing at the pterygopalatine ganglion. Postganglionic fibers reach the gland via maxillary branches of the trigeminal nerve and lacrimal nerve. - **Lymphatic Drainage:** Superficial parotid lymph nodes. - **Blood Supply:** Lacrimal artery (branch of ophthalmic artery); venous return via superior ophthalmic vein. - **Pathology:** Dry eye syndrome (DES) or keratoconjunctivitis sicca (KCS) due to reduced lacrimal fluid production. #### Salivary Glands - **Function:** Produce saliva to lubricate and cleanse the oral cavity, aid digestion, and contribute to immune defense. - **Control:** Autonomic nervous system. - **Types:** Major (large, encapsulated, named ducts) and Minor (smaller, more numerous, unencapsulated, shorter unnamed ducts). Both are exocrine. ##### Major Salivary Glands 1. **Parotid Salivary Gland** - **Type:** Largest encapsulated major salivary gland. - **Secretions:** Serous type only (25% of total salivary volume). - **Location:** Parotid space, posterior to mandibular ramus, anterior and inferior to each ear, overlying the masseter muscle. - **Duct:** Parotid duct (Stensen duct) opens into the oral cavity opposite the maxillary second molar. - **Innervation:** Efferent (parasympathetic) fibers from the otic ganglion of the glossopharyngeal nerve (ninth cranial nerve) via the lesser petrosal nerve. Postganglionic fibers carried by the auriculotemporal nerve (mandibular division of trigeminal nerve). Facial nerve passes through but does not innervate. - **Lymphatic Drainage:** Deep parotid lymph nodes. - **Blood Supply:** Transverse facial artery (branch of external carotid artery); venous return via retromandibular vein. - **Pathology:** Enlargement and tenderness with mumps (parotitis), most salivary gland cancers involve the parotid. 2. **Submandibular Salivary Gland** - **Type:** Second largest encapsulated major salivary gland. - **Secretions:** Mixed serous and mucous (60-65% of total salivary volume). - **Location:** Submandibular fossa in the submandibular space, inferior and posterior to the body of the mandible. - **Duct:** Submandibular duct (Wharton duct) opens at the sublingual caruncle in the floor of the mouth. - **Innervation:** Efferent (parasympathetic) fibers of the chorda tympani nerve (facial nerve) synapsing in the submandibular ganglion. Postganglionic fibers delivered by the lingual nerve (mandibular division of trigeminal nerve). - **Lymphatic Drainage:** Submandibular lymph nodes. - **Blood Supply:** Glandular branches of the facial artery; venous return mainly by the facial vein. - **Pathology:** Most common site for salivary stones (sialoliths). 3. **Sublingual Salivary Gland** - **Type:** Smallest, most diffuse, and only unencapsulated major salivary gland. - **Secretions:** Mixed, predominately mucous (10% of total salivary volume). - **Location:** Sublingual fossa in the sublingual space at the floor of the mouth, deep to the sublingual fold, anterior to the submandibular gland. - **Ducts:** Ducts of Rivinus (8-20 small ducts) open along the sublingual fold; sometimes form a larger Bartholin duct opening at the sublingual caruncle. - **Innervation:** Same as submandibular gland: efferent (parasympathetic) fibers of the chorda tympani nerve (facial nerve) and submandibular ganglion. Postganglionic fibers delivered by the lingual nerve (mandibular division of trigeminal nerve). - **Lymphatic Drainage:** Submandibular lymph nodes. - **Blood Supply:** Sublingual artery (off lingual artery); parallel venous return. ##### Minor Salivary Glands - **Type:** More numerous than major glands, unencapsulated. - **Secretions:** Mainly mucous, except von Ebner glands (serous only). - **Location:** Scattered throughout oral mucosa (buccal, labial, lingual, soft palate, posterior hard palate, floor of mouth). Von Ebner glands associated with circumvallate lingual papillae. - **Ducts:** Single, short ducts directly into the oral cavity. - **Innervation:** Preganglionic from facial nerve, postganglionic from various branches of the trigeminal nerve. - **Lymphatic Drainage & Blood Supply:** Various nodes and arteries depending on location. - **Pathology:** Mucocele (blockage of duct from trauma). #### Thyroid Gland - **Type:** Largest endocrine gland (ductless). - **Secretions:** Thyroxine (hormone) directly into the vascular system to stimulate metabolic rate. - **Location:** Anterolateral regions of the neck, inferior to the thyroid cartilage, at the junction of the larynx and trachea. - **Innervation:** Sympathetic nerves through cervical ganglia (do not control secretion; pituitary gland regulates hormone release). - **Lymphatic Drainage:** Superior deep cervical lymph nodes. - **Blood Supply:** Superior and inferior thyroid arteries (possibly thyroid ima artery); venous return via superior, middle, and inferior thyroid veins. - **Pathology:** Goiter (enlarged thyroid gland), loss of mobility indicating neoplastic growth. #### Parathyroid Glands - **Type:** Usually four small endocrine glands (ductless). - **Secretions:** Parathyroid hormone directly into the vascular system to regulate calcium and phosphorus levels. - **Location:** Adjacent to or within the thyroid gland on its posterior surface (not visible or palpable). - **Innervation:** Same as thyroid gland: sympathetic nerves through cervical ganglia. - **Lymphatic Drainage:** Superior deep cervical lymph nodes. - **Blood Supply:** Primarily inferior thyroid arteries (possibly anastomotic branch between inferior and superior thyroid arteries); venous return via superior, middle, and inferior thyroid veins. #### Thymus Gland - **Type:** Endocrine gland (ductless) and part of the immune system. - **Function:** T-cell lymphocytes mature here. Grows until puberty, then shrinks (involution). - **Location:** Thorax and anterior region of the base of the neck, inferior to the thyroid gland, superficial and lateral to the trachea, deep to the sternum. - **Innervation:** Branches of the vagus nerve (tenth cranial nerve) and cervical spinal nerves. - **Lymphatic Drainage:** Lymphatic system begins within the gland and terminates in the internal jugular vein (no afferent vessels). - **Blood Supply:** Inferior thyroid and internal thoracic arteries; venous return via veins in the posterior surface directly into brachiocephalic veins. - **Pathology:** Thymic rests (ectopic accessory thymic tissue). ## Chapter 10: Lymphatic System ### Summary This chapter covers the lymphatic system, its components (vessels, nodes, ducts, tonsils), and its role in fighting disease. It details the location, drainage patterns, and clinical significance of lymph nodes and tonsils in the head and neck. ### Key Information #### Lymphatic System Overview - **Components:** Vessels, nodes, ducts, tonsils. - **Function:** Part of the immune system, fights infection and cancer, drains tissue fluid (lymph). - **Lymphatic Vessels:** Parallel venous blood vessels, have one-way valves, drain lymph. - **Lymph Nodes:** Bean-shaped bodies in clusters, filter toxic products from lymph, contain lymphocytes (white blood cells), involved in lymphocyte production. - **Afferent vessels:** Lymph flows into the node. - **Efferent vessel:** Lymph flows out of the node at the hilus. - **Primary node (regional/master node):** First node lymph drains into from a particular region. - **Secondary node (central node):** Node that primary nodes drain into. - **Lymphatic Ducts:** Larger vessels formed by converging lymphatic vessels. - **Right lymphatic duct:** Drains right side of head and neck, right arm, and thorax into the junction of the right subclavian and right internal jugular veins. - **Thoracic duct:** Drains left side of head and neck, left arm, thorax, and entire lower half of the body into the junction of the left subclavian and left internal jugular veins. - **Tonsils:** Masses of lymphoid tissue near airway and food passages, contain lymphocytes, drain into superior deep cervical lymph nodes. #### Lymph Nodes of the Head ##### Superficial Lymph Nodes of the Head - **Occipital Lymph Nodes:** - **Location:** Posterior base of the head (occipital region). - **Drainage:** Scalp in the occipital region. - **Empties into:** Deep cervical nodes. - **Posterior Auricular, Anterior Auricular, and Superficial Parotid Lymph Nodes:** - **Posterior Auricular:** Posterior to each auricle and external acoustic meatus. - **Anterior Auricular:** Immediately anterior to each tragus. - **Superficial Parotid:** Superficial to each parotid salivary gland. - **Drainage:** External ear, lacrimal gland, adjacent scalp and face. - **Empties into:** Deep cervical nodes. - **Facial Lymph Nodes:** - **Location:** Along the facial vein. - **Subgroups:** Malar (infraorbital), Nasolabial (along nasolabial sulcus), Buccal (around labial commissure), Mandibular (superior to mandible, anterior to masseter). - **Drainage:** Skin and mucous membranes where located, drain superior to inferior. - **Empties into:** Deep cervical nodes via submandibular nodes. ##### Deep Lymph Nodes of the Head - Cannot be palpated extraorally. - **Deep Parotid Lymph Nodes:** - **Location:** Deep within the parotid salivary gland. - **Drainage:** Middle ear, auditory tube, parotid salivary gland. - **Empties into:** Deep cervical nodes. - **Retropharyngeal Lymph Nodes:** - **Location:** Near deep parotid nodes, at the level of the atlas. - **Drainage:** Posterior palate, pharynx, paranasal sinuses, nasal cavity. - **Empties into:** Deep cervical nodes. #### Cervical Lymph Nodes - Paired, unilaterally drain tissues (except submental nodes, which drain bilaterally). - Categorized into superficial and deep. - Medical community uses a 7-level classification (Node Levels I-VII). ##### Superficial Cervical Lymph Nodes - **Submental Lymph Nodes (Node Level I, Sublevel a):** - **Location:** Inferior to the chin, within the submental fascial space and submental triangle. - **Drainage:** Lower lip, chin, floor of mouth, apex of tongue, mandibular incisors with periodontium and gingiva. - **Empties into:** Submandibular nodes or directly into deep cervical nodes. - **Clinical Significance:** Risk for spread of cancers from floor of mouth, apex of tongue, mandibular anterior alveolar process, lower lip. - **Submandibular Lymph Nodes (Node Level I, Sublevel b):** - **Location:** Inferior border of the mandibular ramus, superficial to the submandibular salivary gland. - **Drainage:** Cheeks, upper lip, body of tongue, anterior hard palate, most teeth (except mandibular incisors and maxillary third molars), sublingual and submandibular salivary glands. Secondary nodes for submental and facial regions. - **Empties into:** Deep cervical nodes. - **Clinical Significance:** Risk for spread of cancers from oral cavity, anterior nasal cavity, midface structures, submandibular salivary gland. - **External Jugular Lymph Nodes (Superficial Cervical Nodes):** - **Location:** Along the external jugular vein, superficial to the SCM muscle. - **Drainage:** Secondary nodes for occipital, posterior auricular, anterior auricular, and superficial parotid nodes. - **Empties into:** Deep cervical nodes. - **Anterior Jugular Lymph Nodes (Anterior Cervical Nodes):** - **Location:** Along the anterior jugular vein, anterior to larynx, trachea, superficial to SCM muscle. - **Drainage:** Infrahyoid region of the neck. - **Empties into:** Deep cervical nodes. ##### Deep Cervical Lymph Nodes - **Location:** Along the internal jugular vein, deep to the SCM muscle, from skull base to root of neck. - Divided into superior and inferior based on omohyoid muscle crossing internal jugular vein. - **Node Level II (Superior one-third):** - **Location:** From digastric muscle superiorly to hyoid bone/carotid bifurcation inferiorly. - **Drainage:** Oral cavity, nasal cavity, nasopharynx, oropharynx, laryngopharynx, larynx, parotid salivary gland. - **Jugulodigastric lymph node (tonsillar node):** Prominent node in this group, drains palatine tonsils. - **Node Level III (Middle one-third):** - **Location:** From hyoid bone/carotid bifurcation superiorly to cricothyroid notch/cricoid cartilage/omohyoid muscle inferiorly. - **Drainage:** Oral cavity, nasopharynx, oropharynx, laryngopharynx, larynx. - **Node Level IV (Inferior one-third):** - **Location:** From omohyoid muscle superiorly to clavicle inferiorly. - **Drainage:** Laryngopharynx, esophagus, larynx. - **Node Level V (Posterior cervical triangle):** - **Location:** From skull base at posterior SCM border to clavicle. - **Drainage:** Nasopharynx, oropharynx (Sublevel a), thyroid gland (Sublevel b). - **Node Level VI (Anterior compartment):** - **Location:** Inferior to hyoid bone, between medial margins of common carotid arteries. - **Drainage:** Thyroid gland, specific parts of larynx, esophagus. - **Superior Deep Cervical Lymph Nodes:** - **Location:** Deep to SCM muscle, superior to omohyoid muscle crossing internal jugular vein. - **Drainage:** Posterior nasal cavity, posterior hard palate, soft palate, base of tongue (bilateral drainage), maxillary third molars, TMJ, esophagus, trachea, thyroid gland. Secondary nodes for most other head and neck nodes. - **Empties into:** Inferior deep cervical nodes or directly into jugular trunk. - **Inferior Deep Cervical Lymph Nodes:** - **Location:** Deep to SCM muscle, inferior to omohyoid muscle crossing internal jugular vein, extending into supraclavicular fossa. - **Drainage:** Posterior scalp and neck, superficial pectoral region, part of arm. Secondary nodes for superficial head nodes and superior deep cervical nodes. - **Jugulo-omohyoid lymph node:** Drains tongue and submental triangle; enlarged node can indicate tongue carcinoma. - **Empties into:** Jugular trunk (right) or thoracic duct (left). - **Clinical Significance:** Communicates with axillary lymph nodes, high risk for spread of breast cancer. - **Accessory Lymph Nodes:** - **Location:** Along the eleventh cranial (accessory) nerve. - **Drainage:** Scalp and neck regions. - **Empties into:** Supraclavicular nodes. - **Supraclavicular Lymph Nodes:** - **Location:** Superiorly along the clavicle. - **Drainage:** Lateral cervical triangles. - **Empties into:** Jugular trunks or directly into right lymphatic duct/thoracic duct. - **Clinical Significance:** Final endpoint of lymphatic drainage from entire body, high risk for spread of cancers from lungs, esophagus, stomach. #### Tonsils - **Palatine Tonsils:** - **Location:** Oral cavity, between anterior and posterior faucial pillars. - **Lingual Tonsil:** - **Location:** Dorsal surface of the base of the tongue. - **Pharyngeal Tonsil (Adenoids):** - **Location:** Midline of the posterior wall/roof of the nasopharynx. - **Tubal Tonsil:** - **Location:** Nasopharynx, posterior to openings of the auditory tube. - **Drainage:** All tonsils drain into the superior deep cervical lymph nodes, particularly affecting the jugulodigastric lymph node if infected. #### Clinical Considerations with Lymphatic System Pathology - **Lymphadenopathy:** Dramatic increase in size and change in consistency of lymphoid tissue due to infection or cancer. - **Infection:** Nodes are slightly firmer, extremely mobile, and tender. - **Cancer:** Nodes can become bony hard, fixed to surrounding tissue, usually not tender initially (pain is a late finding). - **Lymphadenitis:** Inflammation of a lymph node, common with microbial infections. - **Metastasis:** Spread of cancer from a primary site to a secondary site via lymph. - Involvement of primary nodes offers a better prognosis than secondary nodes or lymphatic ducts. - Head and neck cancers frequently spread to cervical lymph nodes (80% of cases). - Node metastasis is a significant prognostic factor for squamous cell carcinoma survival. ### Learning Objectives Tasks: - Define and pronounce key and anatomic terms. - Locate and identify glands and associated structures on diagrams, skulls, and patients. - Discuss glandular pathology. - Integrate understanding into clinical dental practice. - List and discuss lymphatic system components. - Locate and identify lymph nodes and tonsils on diagrams and patients. - Identify lymphatic drainage patterns for the head and neck. - Describe and discuss pathology of lymphoid tissue. - Compare the relationship of the lymphatic system to the overall function of the immune system.

Chapter 4 Skin and Body Membranes Body Membranes Functions of body membranes Cover body surfaces Line body cavities Form protective sheets around organs Classified according to tissue types Body Membranes Two major categories Epithelial membranes Cutaneous membranes Mucous membranes Serous membranes Connective tissue membranes Synovial membranes Epithelial Membranes Epithelial membranes are simple organs Also called covering and lining membranes These membranes contain both: Epithelial tissue layer Connective tissue layer Epithelial Membranes Cutaneous membrane = skin Dry membrane Outermost protective boundary Consists of two layers Epidermis is composed of keratinized stratified squamous epithelium Dermis is mostly dense (fibrous) connective tissue Epithelial Membranes • Mucous membranes (mucosae) • I Moist membranes Some mucosae secrete protective, lubricating mucus Line all body cavities that open to the exterior body surface • Adapted for absorption or secretion • ' Consists of two layers • Epithelium type depends on site • Loose connective tissue (lamina propria) Epithelial Membranes Serous membranes (serosae) Line compartments in the ventral body cavity that are ciosed to the exterior of the body Occur in pairs, separated by serous fluid, with a visceral and parietal layer Consists of two layers Simple squamous epithelium Areolar connective tissue Epithelial Membranes Specific serous membranes Peritoneum Cover organs in the abdominal cavity Pleurae Surround the lungs Pericardia Surround the heart Connective Tissue Membranes Synovial membranes Loose areolar connective tissue only (no epithelial tissue) Line fibrous capsules surrounding joints Line bursae Line tendon sheaths Secrete a lubricating fluid to cushion organs moving against each other during muscle activity Integumentary System Integumentary system consists of the: Skin (cutaneous membrane) Skin appendages Sweat glands Oil glands Hair Nails Functions of the Integumentary System Insulates and cushion deeper body organs Protects the entire body from: Mechanical damage (bumps and cuts) Chemical damage (acids and bases) Thermal damage (heat or cold) Ultraviolet (UV) radiation (sunlight) Microbes (bacteria) • Water loss Functions of the Integumentary System Regulates heat loss as controlled by the nervous system Acts as a mini-excretory system; sweat aids in the loss of Urea Salts Water Synthesizes vitamin D Secretions create a protective acid mantle Structure of the Skin Two kinds of tissue compose the skin Epidermis Dermis Subcutaneous tissue (hypodermis) Anchors the skin to underlying organs Not technically part of the integumentary system Composed mostly of adipose tissue Serves as a shock absorber and insulates deeper tissues Structure of the Skin Epidermisouter layer Composed of stratified squamous epithelium Most cells are keratinocytes which produce a fibrous protein called keratin Keratinization makes the epidermis tough Desmosomes connect keratinocytes together Avascular Composed of five layers (strata) Structure of the Skin Summary of strata (layers) of the epidermis from deepest to most superficial Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum (thick, hairless skin only) Stratum corneum Structure of the Skin Stratum basale (stratum germinativum) Deepest layer of epidermis Lies next to dermis Wavy borderline with the dermis anchors the two together Cells undergoing mitosis Daughter cells are pushed upward to become the more superficial layers Stratum spinosum Cells become increasingly flatter and more keratinized Structure of the Skin Stratum granulosum Stratum lucidum Formed from dead cells of the deeper strata Occurs only in thick, hairless skin of the palms of hands and soles of feet Stratum corneum Outermost layer of epidermis Shingle-like dead cells are filled with keratin (protective protein prevents wat loss from skin Structure of the Skin Melanin Melanin is a pigment produced by melanocytes Melanocytes are mostly in the stratum basale of the epidermis Color is yellow to brown to black Structure of the Skin Epidermal dendritic cells Alert and activate immune cells to a threat (bacterial or viral invasion) Merkel cells Associated with sensory nerve endings Serve as touch receptors called Merkel discs Structure of the Skin Dermis Connective tissue Underlies the epidermis Two regions Papillary Reticular Structure of the Skin Two regions of the dermis Papillary layer (upper dermal region) contain projections called dermal papillae Areolar connective tissue Indent the epidermis above Many projections contain capillary loops, and others house pain and touch receptors On palm and sole surfaces, papillae increase friction and gripping ability Fingerprints are identifying films of sweat Structure of the Skin Two regions of the dermis Reticular layer (deepest skin layer) Dense irregular connective tissue Blood vessels Sweat and oil glands Deep pressure receptors (lamellar corpuscles) Structure of the Skin Other dermal features Cutaneous sensory receptors Phagocytes Collagen and elastic fibers Blood vessels I Nerve supply Skin Color • Three pigments contribute to skin color 1. Melanin • Yellow, reddish brown, or black pigments 2. Carotene • Orange-yellow pigment (also found in some vegetables) 3. Hemoglobin Red coloring from blood cells in dermal capillaries Oxygen content determines the extent of red coloring Skin Color Redness (erythema) due to embarrassment, inflammation, hypertension, fever, or allergy Pallor (blanching) due to emotional stress (such as fear), anemia, low blood pressure, impaired blood flow to an area Jaundice (yellow cast)-indicates a liver disorder • Bruises (black and blue marks)-hematomas Appendages of the Skin Cutaneous glands are all exocrine glands Sebaceous glands Sweat glands Hair and hair follicles Nails Appendages of the Skin Sebaceous (oil) glands Located all over the skin except for palms and soles Produce sebum (oil) Makes skin soft and moist Prevents hair from becoming brittle Kills bacteria Most have ducts that empty into hair follicles; others open directly onto skin surface Glands are activated at puberty with increased androgens Appendages of the Skin Sweat (sudoriferous) glands Produce sweat Widely distributed in skin Two types of sudoriferous glands Eccrine glands Apocrine glands Appendages of the Skin Eccrine glands More numerous, located all over the body Open via duct to sweat pores on the skin's surface Produce acidic sweat Water, salts, vitamin C, traces of metabolic waste Function in body temperature regulation Appendages of the Skin Apocrine glands Ducts empty into hair follicles in the armpit and genitals Begin to function at puberty Release sweat that also contains fatty acids and proteins (milky or yellowish color) • Play a minimal role in body temperature regulation Appendages of the Skin Hair Located body-wide except for palms, soles, nipples, lips Produced by hair follicle Root is enclosed in the follicle Shaft projects from the surface of the scalp or skin Consists of hard keratinized epithelial cells Melanocytes provide pigment for hair color Hair grows in the matrix of the hair bulb in stratum basale Appendages of the Skin Hair anatomy Central medulla Cortex surrounds medulla Cuticle on outside of cortex Most heavily keratinized region of the hair Melanin provides color Appendages of the Skin Associated hair structures Hair follicle Composed of an inner epithelial root sheath andan outer fibrous sheath Dermal region provides a blood supply to the hair bulb (deepest part of the follicle) Arrector pili muscle connects to the hair follicle to pull hairs upright when we are cold or frightened Appendages of the Skin Nails Heavily keratinized, scalelike modifications of the epidermis Stratum basale extends beneath the nail bed, which is responsible for growth Lack of pigment makes nails colorless Appendages of the Skin Parts of a nail Free edge Body is the visible attached portion Nail folds are skin folds that overlap the edges of the nail; the cuticle is the proximal edge Root of nail is embedded in skin Growth of the nail occurs from nail matrix of nail bed Homeostatic Imbalances of Skin Infections and allergies Athlete's foot Caused by fungal infection (Tinea pedis) Itchy, red peeling skin between the toes Boils (furuncles) and carbuncles Caused by inflammation of hair follicles Carbuncles are clusters of boils caused by bacteria Cold sores (fever blisters) Caused by human herpesvirus 1 Blisters itch and sting Homeostatic Imbalances of Skin Infections and allergies Contact dermatitis Caused by exposure to chemicals that provoke allergic responses Itching, redness, and swelling of the skin Impetigo Caused by bacterial infection Pink, fluid-filled raised lesions around mouth/nose Psoriasis Triggered by trauma, infection, hormonal changes, or stress Red, epidermal lesions covered with dry, silvery scales that itch, burn, Crack, or sometimes bleed Homeostatic Imbalances of Skin • Burns Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals Associated dangers Protein denaturation and cell death Dehydration and electrolyte imbalance Circulatory shock Result in loss of body fluids and infection from the invasion of bacteria Homeostatic Imbalances of Skin Extent of a burn is estimated using the rule of nines Body is divided into 11 areas for quick estimation Each area represents about 9 percent of total body surface area The area surrounding the genitals (the perineum) represents 1 percent of body surface area Homeostatic Imbalances of Skin . First-degree burn (superficial burn) Only epidermis is damaged Skin is red and swollen Second-degree burn (superficial partial-thickness burn) Epidermis and superficial part of dermis are damaged Skin is red, painful, and blistered Regrowth of the epithelium can occur Homeostatic Imbalances of Skin Third-degree burn (full-thickness burn) Destroys epidermis and dermis; burned area is painless Requires skin grafts, as regeneration is not possible Burned area is blanched (gray-white) or black Fourth-degree burn (full-thickness burn) Extends into deeper tissues (bone, muscle, tendons) Appears dry and leathery Requires surgery and grafting May require amputation Homeostatic Imbalances of Skin Criteria for deeming burns critical (if any one is met): Over 30 percent of body has second-degree burns Over 10 percent of the body has third-or fourth-degree burns Third-or fourth-degree burns of the face, hands, feet, or genitals Burns affect the airways Circumferential (around the body or limb) burns have occurred Homeostatic Imbalances of Skin Skin cancer Most common form of cancer in humans Most important risk factor is overexposure to ultraviolet (V) radiation in sunlight and tanning beds Cancer can be classified two ways Benign means the neoplasm (tumor) has not spread Malignant means the neoplasm has invaded other body areas Concept Link Recall that mitosis gone wild is the basis for cancer (Chapter 3, pp. 82-83). These cells lack normal control of cell division and divide quickly, resulting in errors during DNA replication, mitosis, or both. Cells experiencing rapid, uncontrolled growth become cancerous and can metastasize (spread) to other parts of the body. Homeostatic Imbalances of Skin . First-degree burn (superficial burn) Only epidermis is damaged Skin is red and swollen Second-degree burn (superficial partial-thickness burn) Epidermis and superficial part of dermis are damaged Skin is red, painful, and blistered Regrowth of the epithelium can occur Homeostatic Imbalances of Skin Third-degree burn (full-thickness burn) Destroys epidermis and dermis; burned area is painless Requires skin grafts, as regeneration is not possible Burned area is blanched (gray-white) or black Fourth-degree burn (full-thickness burn) Extends into deeper tissues (bone, muscle, tendons) Appears dry and leathery Requires surgery and grafting May require amputation Homeostatic Imbalances of Skin Criteria for deeming burns critical (if any one is met): Over 30 percent of body has second-degree burns Over 10 percent of the body has third-or fourth-degree burns Third-or fourth-degree burns of the face, hands, feet, or genitals Burns affect the airways Circumferential (around the body or limb) burns have occurred Homeostatic Imbalances of Skin Skin cancer Most common form of cancer in humans Most important risk factor is overexposure to ultraviolet (V) radiation in sunlight and tanning beds Cancer can be classified two ways Benign means the neoplasm (tumor) has not spread Malignant means the neoplasm has invaded other body areas Concept Link Recall that mitosis gone wild is the basis for cancer (Chapter 3, pp. 82-83). These cells lack normal control of cell division and divide quickly, resulting in errors during DNA • One or more of the ABCD characteristics is evolving Developmental Aspects of Skin and Body Membranes Lanugo, a downy hair, covers the body by the fifth or sixth month of fetal development but disappears by birth Vernix caseosa, an oily covering, is apparent at birth Milia, small white spots, are common at birth and disappear by the third week Acne may appear during adolescence Pimples, scales, and dermatitis are more common with aging skin Developmental Aspects of Skin and Body Membranes In youth, skin is thick, resilient, and well hydrated With aging, skin loses elasticity and thins Skin cancer is a major threat to skin exposed to excessive sunlight Balding (alopecia) and/or graying occurs with aging; both are genetically determined other factors that may contribute include drugs and emotional stress