Skin and Body Membranes

Skin and Body Membranes

• Body membranes cover body surfaces, line body cavities, and form protective sheets around organs
• Body membranes are classified according to tissue type.

Epithelial Membranes

• Epithelial membranes are simple organs; also called covering and lining membranes
• Epithelial membranes contain an epithelial tissue layer and a connective tissue layer
• Cutaneous membranes are skin; a dry membrane and the outermost protective boundary
• The epidermis is composed of keratinized stratified squamous epithelium
• The dermis is mostly dense (fibrous) connective tissue
• Mucous membranes (mucosae) are moist membranes that line all body cavities open to the exterior
• Mucous membranes are adapted for absorption or secretion
• They are constructed from an epithelium adapted to the site with loose connective tissue (lamina propria)
• Serous membranes (serosae) line open body cavities that are closed to the exterior.
• They always occur in pairs, separated by serous fluid, with a visceral and parietal layer.
• Serous membrane construction is simple squamous epithelium resting on areolar connective tissue

Specific Serous Membranes

• The peritoneum lines the abdominal cavity
• The pleura surrounds the lungs
• The pericardium surrounds the heart

Connective Tissue Membranes

• Synovial membranes are loose areolar connective tissue only (no epithelial tissue)
• They line fibrous capsules surrounding joints, bursae, and tendon sheaths
• Synovial membranes secrete a lubricating fluid to cushion organs moving against each other

Integumentary System

• The integumentary system consists of skin (cutaneous membrane), skin appendages, sweat glands, oil glands, hair, and nails
• Integumentary system functions include insulation, cushioning deeper body organs, and protection
• It protects the entire body from mechanical damage, chemical damage, microbe and UV radiation damage etc
• It aids in body heat loss or retention controlled by the nervous system
• It aids in excretion of urea and uric acid and synthesizes vitamin D

Structure of the Skin

• Two kinds of tissue compose the skin: the epidermis and the dermis
• The hypodermis (subcutaneous layer) anchors the skin to underlying organs
• It is not technically part of the integumentary system; is composed mostly of adipose tissue
• It serves as a shock absorber and insulates deeper tissues

Epidermis – Outer Layer

• The epidermis is capable of being hard and tough and consists of stratified squamous epithelium
• Keratinocytes (the most common cell) produce a fibrous protein called keratin
• Avascular
• Consists of five layers (strata): stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum

Summary of Epidermis Layers (Deepest to Superficial)

• Stratum basale: Deepest layer; lies next to dermis, wavy borderline anchors the two together
• Cells are undergoing mitosis, daughter cells are pushed to become more superficial layers
• Stratum spinosum: Cells become increasingly flatter and more keratinized
• Stratum granulosum
• Stratum lucidum: Formed from dead cells of the deeper strata
• Stratum corneum: Outermost layer with shingle-like dead cells filled with keratin that prevent water loss

Melanin

• Melanin is a pigment produced by melanocytes that are mostly in the stratum basale
• Color is yellow to brown to black
• Melanin accumulates in membrane-bound granules called melanosomes
• The amount of melanin produced depends upon genetics and exposure to sunlight

Epidermal Dendritic Cells

• Epidermal dendritic cells alert and activate immune cells to a bacterial or viral invasion

Merkel Cells

• Merkel cells are associated with sensory nerve endings and serve as touch receptors called Merkel discs

Dermis

• The dermis is connective tissue underlying the epidermis
• There are two layers of the dermis: the papillary layer and the reticular layer

Papillary layer

• The papillary layer contains projections called dermal papillae which indent the epidermis above
• Many projections contain capillary loops and others house pain and touch receptors
• Papillae increases friction and gripping ability on palm and sole surfaces; fingerprints are identifying films of sweat

Reticular Layer

• The reticular layer is the deepest skin layer and contains blood vessels, sweat and oil glands, and deep pressure receptors (lamellar corpuscles)

Other Dermal Features

• Cutaneous sensory receptors
• Phagocytes
• Collagen and elastic fibers
• Blood vessels

Skin Color

• Skin color determinants are melanin, carotene, and hemoglobin

Melanin

• Melanin has yellow, reddish brown, or black pigments

Carotene

• Carotene is an orange-yellow pigment from some vegetables

Hemoglobin

• Hemoglobin refers to red coloring from blood cells in dermal capillaries
• Oxygen content determines the extent of red coloring

Other

• Redness (erythema) is due to embarrassment, inflammation, hypertension, fever, or allergy
• Pallor (blanching) is due to emotional stress (fear), anemia, low blood pressure, or impaired blood flow
• Jaundice (yellow cast) indicates a liver disorder
• Bruises (black and blue marks) are hematomas

Appendages of the Skin

• Cutaneous glands are all exocrine glands that include sebaceous glands and sweat glands
• Other Skin Appendages include hair, hair follicles, and nails

Sebaceous (Oil) Glands

• Sebaceous glands are located all over the skin except for palms and soles
• Produce sebum (oil) that makes skin soft and moist, prevents hair from becoming brittle, and kills bacteria
• Most have ducts that empty into hair follicles; others open directly onto the skin surface
• Glands are activated at puberty

Sweat (Sudoriferous) Glands

• Sweat (sudoriferous) glands widely distributed in the skin produce sweat
• There are two types of sudoriferous glands; eccrine glands and apocrine glands
• Eccrine glands open via a duct to sweat pores on the skin's surface and produce acidic sweat containing water, salts, vitamin C, and traces of metabolic waste
• Apocrine glands ducts empty into hair follicles in the armpit and genitals; begin to function at puberty
• They release sweat that also contains fatty acids and proteins (milky or yellowish color) and play a minimal role in body temperature regulation

Hair

• Hair is produced by a hair follicle and its root is enclosed in it
• Shaft projects to the surface of the scalp or skin
• Hairs consist of hard keratinized epithelial cells
• Melanocytes provide pigment for hair color
• Hair grows in the matrix of the hair bulb in the stratum basale

Hair Anatomy

• Central medulla
• Cortex that surrounds medulla
• Cuticle on outside of cortex
• The cuticle is the most heavily keratinized region of the hair

Associated Hair Structures

• The hair follicle is composed of an epithelial root sheath and fibrous sheath
• The dermal region provides a blood supply to the hair bulb
• Arrector pili muscle connects to the hair follicle to pull hairs upright when we are cold or frightened

Nails

• Nails are heavily keratinized, scalelike modifications of the epidermis
• The stratum basale extends beneath the nail bed and is responsible for growth
• Lack of pigment makes nails colorless

Parts of a Nail

• Free edge
• Body is the visible attached portion
• Nail folds are skin folds that overlap the edges of the nail
• Root of nail is embedded in skin and growth occurs in nail matrix

Homeostatic Imbalances of the Skin

• Homeostatic imbalances include infections and allergies, burns, skin cancer

Infections and Allergies

• Athlete's foot is caused by a fungal infection (Tinea pedis) that causes itchy, red, peeling skin between the toes
• Boils (furuncles) and carbuncles are caused by inflammation of hair follicles as well as clusters of boils caused by bacteria
• Cold sores (fever blisters) are caused by human herpesvirus 1 that make blisters itch and sting
• Contact dermatitis is caused by exposure to chemicals that provoke allergic responses that cause itching, redness, and swelling of the skin
• Impetigo is caused by bacterial infection that causes pink, fluid-filled raised lesions around the mouth/nose
• Psoriasis is triggered by trauma, infection, hormonal changes, or stress with red, epidermal lesions covered with dry, silvery scales

Burns

• Burns cause tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals
• Associated dangers are protein denaturation, cell death, dehydration, electrolyte imbalance and circulatory shock
• Results in loss of body fluids and infection
• Body divided into 11 areas for quick estimation, each area equals about 9% of surface area, genitals represent 1% of body face area

Rule of Nines

• 1st degree burns: epidermis is damaged, skin red and swollen
• 2nd degree burns: epidermis and upper part of superficial dermis damaged, blistered, and skin is red and painful
• 3rd degree burn: destroys epidermis and dermis
• 4th degree burn: extends into deeper tissues

Skin Cancer

• Three degree- 4th degree burns of the face hands, feet or genitals burns effect airways and burns having circumference over the body

Classification

• Benign: means the neoplasm (tumor) has not spread
• Malignant: means tumor has invaded other body areas

Basal Cell Carcinoma

• Least malignant, most common cancer type, arises from stratum basale
• Early removal allows good chance for cure and metastasizes if not removed

Malignant Melanoma

• Most deadly skin cancer, but only accounts for about 5%
• Arises from melanocytes and metastasizes
• Spot has the characteristics for "The ABCDE Rule"

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
• In youth, skin is thick, resilient, and well-hydrated
• With aging, skin loses elasticity and thins
• Balding and/or graying occurs with aging; both are genetically determined
• Skin cancer is a major threat to skin exposed to excessive sunlight

Skeletal System

• The skeletal system parts are bones, joints, cartilages, ligaments
• There are two subdivisions: the axial skeleton and the appendicular skeleton

Function of Bones

• Support the body
• Protect soft organs via rib cage and skull
• Allow skeletal muscles movement
• Store minerals and fats
• Blood formation (hematopoiesis)

Bone Classification

• Adult skeleton has 206 bones
• Includes compact and spongy bone
• Classified by shape as long, flat, short and irregular

Long Bones

• Typically longer than are wide and composed of compact bone

Flat bones

• Thin, flattened and have two compact bones, sandwiching spongy bone

Short bones

• Generally cube-shaped and consisting of spongy and compact bone

Irregular bones

• Irregular shape

Bone Anatomy

• The diaphysis is the shaft which makes up most of length and composed of compact bone
• The periosteum is the outside covering of the diaphysis which is a fibrous connective tissue membrane and held on by perforating fibers to the underlying bone

Bone - Epiphysis

• Epiphysis contains spongy and compact
• Outside surface is covered by articular cartilage and has minimal friction
• Remnant of epiphyseal plate

Bones - Bone Markings

• Terms beginning with “T” are projections or processes that grow out of the bone surface
• Terms “F” are depressions or cavities which are indentations in the bones

Bones - Microscopic Anatomy Compact

• Osteocyctes maintain the bone
• Lacunae are space which the bone holds
• Lamellae are rings around the osteon
• Central canal the middle of the bone
• Canaliculi tiny branches from the central canal and the lacunae

Bones - Cartilage

• Bone is lighter than most
• Resists to tension and other forces
• Mineral calcium deposition makes bone harder and able to compress

Bone Production + Growth + Remodeling

• Ossification is process of putting together the bone
• Two phases of long bone production
• Hyaline models cover it in matrix
• Cartilage is digested and opens the medullary cavity

Bone Production - Long bone width

• Appositional growth
  • Bone growth in width
  • Bones grow on outside, osteoclasts destroy bone on inside
• Hormones help control bone growth as well as sex hormones
• More calcium when there is not enough
  • Activates osteoclasts
  • Osteoclasts then break down bone to create ions into the blood

Bones - Fractures

• Four types if fracture
  • Haematoma is blood swelling
  • Splints the broken bone
• Bony callus covers all
• Responds and remodels

Fractures - Types

• Broken in more than one place
• Bone is crushed
• Depressed inwards
• Ends pushed into each other
• Breaks with twists

Axial Skeleton

• Forms longitudinal axis of the body
  • Skull, vertebra and Bony Thorax
• Functions in movement
• Two bones that form the brain include cranium that holds the brain and facial bones
• Bones are joined with sutures

Axial Skeleton: Skull

• Only the mandible is attached with joints
• Brain is able to stay connected because the sutures

The Vertebral column

• Is support to what your body needs
• From the skull to the pelvis and has 26 bones separated

Axial Skeleton: Ribs(Thoracic Cage)

• Consists of three parts: sternum, ribs and thoracic vertebrae
• All of it helps protects the thoracic and protects inside

Appendicular skeleton:Limbs

• Composed of 126 bones
  • Sternum plus limbs are pectoral plus pelvic girdle

Bones: Shoulder Girdle

• Aids in upper limbs and axial skeletal Two bones that connect Clavicle plus scapula

Upper and Lower limbs

• Two major parts of long bone growth
  • 1. cartilage covers the models with matrix
• 2. encloses cartilage digested to medullary cavity There's new articulation that is continuously breaking the Births has two regions along bone 1. cartilaginous (articular) 2. epiphyseal plates

Lower Limb - Pelvic Girdle

• Formed with two coxal bones; composed with trio of fused bones: Ilium, Scaprum+ Pubis
• Bone of the body has to rest on pelvis

Joints

• Occur in places were bones meet one another
• Functions; has to hold bones and allow mobility

Classifying Joints

• Based on how much it can move + Structurally
• Functional joints classified Synarthroses; amphiarthroses: slightly able to move and dyathoroses

Structural Joints

• Structural classified as fiberous (moveable), cartilaginous or Synovial

Fibrous Joints

• Is united by fiberous tissue & immobile
• Suture is immobile
• Allow movement ,still immobile
• On ends of tibia/fibula

Cartilaginious Joints

• is connected by fibrocartilage w/ Types
• Immobile synchondrosis and symphysis

Synovial Joints

• Separated w/ joint + synovial with Four features
• Articular cartilage + Joints capsules + Ligaments and Bursea is flattened with synovial

Types(Synovial Joints) based

• Types (synovial joints) based: Plane,Hinge, Pivot + Saddle etc

Skeletal:Developmental

• Starts with fetal cartilage
• Bones is medullary by fetal
• -- Fontanels are fiberous that "soft spots" -- Allows growth