Exam 3: Integumentary & Skeletal Systems

• epidermis (superficial)

• dermis

• hypodermis (deep)

What are the three major layers of skin?

1. stratum corneum: superficial, 20-30 layers of dead skin cells, protective against abrasion and infection

2. stratum lucidum: only found in thick skin, translucent

3. stratum granulosum: keratinocytes begin keratinization, keratin accumulates and cells start to die

4. stratum spinosum: mostly keratinocytes from basale

5. stratum basale: deepest, contains keratinocyte stem cells, melanocytes, and tactile cells

name the five layers of epidermis

thick: palms of hands, soles of feet, etc., also contains sweat glands

thin: most of the body, contains sweat glands, hair follicles, and sebaceous glands, NO stratum lucidum

Where can thick and thin skin be found?

1. sensing stimuli through cutaneous receptors (tactile and lamellar corpuscles)

2. excretion of waste

3. regulating body temperature

4. protects the body from the outside world

What are the 4 functions of skin?

Hair

1. protection (from sunburn and injury)

2. heat retention

3. sensory reception

Nails

1. provides tips of fingers and toes protection

2. tactile sensation

What are the functions of the hair and nails?

the skin releases sweat to keep the body at a comfortable, cool temperature

dermal blood vessels constrict (vasodilate) and redirect blood to vital organs in cold temperatures

How does the skin regulate body temperature?

as new cells are being constantly produced in the stratum basale, skin cells migrate upwards towards the skin’s surface

cells die at the surface because they produce keratin and lose their nucleus

How do skin cells migrate to the skin surface, and why do they die as they get closer to the surface?

1. papillary layer, superficial (areolar CT)

2. reticular layer, deep (dense irregular CT)

What are the two layers of dermis and what type of connective tissue are they composed of?

• protection

• energy storage

• insulation

made of areolar and adipose CT

What are the functions of the hypodermis (subcutaneous layer)?

1. hemoglobin

   1. creates a bright red color that can be seen in light skin

2. melanin

   1. dark pigment produced in melanocytes, eumelanin: shades of brown and black, pheomelanin: lighter shades of tan and yellow

3. carotene

   1. yellow-orange pigment acquired from some veggies

What three substances contribute to skin color?

people that live(d) near the equator are exposed to higher levels of UV light, which means they need darker pigments in their skin for protection

Why do some ancestral populations have darker skin than other populations?

1. cyanosis

   1. blue skin, may indicate heart failure, poor circulation, or respiratory issues

2. jaundice

   1. yellow skin, liver disorder (bile accumulation in bloodstream)

3. erythema

   1. red skin, could indicate fever, inflammation, or allergy

4. albinism

   1. white hair and pale skin, enzymes needed to produce melanin are nonfunctional, genetic

List four conditions of abnormal skin color

1. nevus (mole)

   1. localized growth of melanocytes

2. freckles

   1. brown spots, localized areas of increased melanocyte activity (NOT an increase in numbers of melanocytes)

3. hemangiomas

   1. skin discoloration due to benign blood vessel tumor

4. friction ridges

   1. fingerprints, they help increase friction when grabbing items or walking barefoot)

List four skin markings and what causes them

1. lanugo hair

   1. fine, unpigmented hair that appears on a fetus in the last trimester of development

2. vellus hair

   1. replaces lanugo hair, also fine and can be lightly pigmented, found on the upper and lower limbs

3. terminal hair

   1. coarse, pigmented longer hair, found on the scalp, eyebrows, eyelashes, face (beard), axillary, and pubic regions

What are the three types of hair? And where are they found on the body, and at what life stage?

1. merocrine sweat gland

   1. most common sweat gland, discharges sweat by exocytosis onto the skin’s surface

2. apocrine sweat gland

   1. releases sweat into hair follicles

3. sebaceous gland (holocrine)

   1. produces an oily and waxy secretion called sebum that is discharged into a hair follicle and onto the hair

What three exocrine glands are found in the skin?

1. first degree burn

   1. only affects the epidermis, characterized by slight redness and pain

2. second degree burn

   1. affects the epidermis and part of the dermis, skin is blistered and painful, slight scarring

3. third degree burn

   1. affects the epidermis, dermis, and hypodermis, severe scarring and skin grafting is typically needed

List and describe the three types of skin burns

UVA and UVB

What types of UV light does sunscreen block?

dermis

this part of the skin does not have rapid cell turnover so the ink remains for a long time

Where is tattoo ink injected?

1. brittle nails

   1. prone to vertical splitting

2. ingrown nails

   1. edge of nail dio0gs into the skin around it

3. onychomycosis

   1. fungal infection of the nail

4. yellow nail syndrome

   1. growth and thickening of the nail slows, nails can become yellow or greenish

5. Beau’s Lines

   1. horizontal white lines, indicates temporary interference with nail growth

6. vertical ridging

List and describe six types of nail disorders?

botox is short for Botulinum toxin type A, it is a toxin derived from C. botulinum that can be injected into the skin

it blocks nerve impulses to facial expression muscles to decrease or eliminate wrinkles

What is botox and what does it do?

• alopecia areata

  • autoimmune disease where follicles area attacked, results in spots of baldness

• diffuse hair loss

  • hairs shed from parts of the scalp

• male pattern baldness

  • loss of hair, first from the crown region of scalp

• hirsutism

  • excessive hairiness

Describe the following hair growth and loss conditions:

alopecia areata, diffuse hair loss, male pattern baldness, and hirsutism

chronic autoimmune disorder where keratinocytes are attacked by T-lymphocytes, results in rapid overgrowth of skin cells, looks like white, scaly skin

What is psoriasis?

bones, tendons, ligaments, and cartilage

What organs and components make up the skeletal system?

• structural support and protection of tissues and organs

• levers for movement (muscles and tissues attach to bone and contract)

• storage of mineral and energy reserves (calcium and phosphate, yellow bone marrow)

What are the functions of the skeletal system?

white, dense, and rigid connective bone tissue

consists of osteons, the basic functional and structural units of mature compact bone

function: support and protection

What is compact bone?

less dense, porous, inner layer of bone CT

made of narrow rods and plates of bone called trabeculae where bone marrow can be stored, if present

function: resists stresses applied to bone, house bone marrow, and site of hematopoiesis

What is spongy bone?

a thin layer of hyaline cartilage that helps reduce friction and absorb shock in movable joints

found at the ends of the humerus, femur, and tibia

What is and where can you find articular cartilage?

1. periosteum

   1. tough sheath that covers the outer surface of bone

   2. protects bone, anchors blood vessels and nerves, and attaches tendons and ligaments to bone

   3. composed of a layer of collagen fibers, a cellular layer, and a fibrous layer

2. endosteum

   1. covers the internal surface of the medullary cavity

   2. consists of osteoprogenitor cells, osteoblasts, and osteoclasts

   3. active during bone growth, repair, and modeling

What are the two layers (membranes) of bone and what do they do?

1. osteoprogenitor cells

   1. stem cells derived from mesenchyme in periosteum; during cell division, one daughter cell becomes another stem cell and the other one is a committed cell (a cell that will differentiate into an osteoblast)

2. osteoblasts

   1. synthesizes and secretes osteoid, an organic form of bone matrix that calcifies as a result of salt crystal deposition

   2. during calcification, these cells become trapped and differentiate into osteocytes

3. osteocytes

   1. mature bone cells that maintain the bone matrix and detect bone stress (if detected, osteoblasts are signaled)

4. osteoclasts

   1. phagocytic cells that break down bone in a process called bone resorption

What are the four types of bone cells and what are their functions?

osteoid is secreted and later on, salt crystals deposit around the collagen fibers in the osteoid, which results in calcification

vitamin D, vitamin C, calcium, and phosphate are also used in this process

How do osteoblasts create bone tissue?

enzymes are released from lysosomes to chemically digest organic components of bone

HCl also dissolves calcium and phosphate and the liberated ions enter the bloodstream

How do osteoclasts remove bone?

clasts originate from hematopoietic stem cells in the bone marrow, similar to cells that produce monocytes

How is osteoclast development different from osteoblast and osteocyte development?

osteoprogenitor stem cells

where do osteoblasts come from?

osteoblasts that have lost their ability to form bone

Where do osteocytes come from?

• organic components

  • osteoid that consists of collagen and ground substance made of glycoproteins and proteoglycans

  • function: gives bone strength by resisting stretching and also gives bone flexibility

• inorganic components

  • salt crystals of calcium phosphate called calcium hydroxyapatite

  • function: crystals deposit around collagen fibers to harden the bone matrix (ossification)

What components make up the bone matrix and what are their functions? (organic and inorganic)

red bone marrow is hematopoietic and yellow bone marrow is the product of RBM degeneration as kids mature (YBM is fatty and may convert back to RBM in cases of severe anemia)

What is the difference between red and yellow bone marrow?

• children

  • spongy bone and medullary cavity of long bones

• adults

  • only found in parts of the axial skeleton such as the skull and vertebrae, also in the heads of the femur and humerus

Where can red bone marrow be found in children and adults?

• children

  • as kids get older, some of their RBM converts to YBM and can be found in the medullary cavity of long bones

• adults

  • medullary cavity of long bones like the femur and humerus

Where can yellow bone marrow be found in children and adults?

bone growth in a membrane, happens during fetal development, produces flat bones, facial bones, mandible, and clavicle

1. ossification centers form within thickened regions of mesenchyme in the eighth week of development (regions consist of osteoblasts and osteoid)

2. osteoid undergoes calcification (calcium salts are deposited into osteoid and solidifies, osteoblasts become trapped and become osteocytes)

3. woven bone and surrounding periosteum form (woven bone is immature, primary bone; periosteum is created)

4. lamellar (secondary) bone replaces woven bone, compact and spongy bone form

What is intramembranous ossification and what are the four steps?

bone formation that begins with hyaline cartilage and produces most bones of the skeleton including upper and lower limbs, pelvis, and vertebrae

1. fetal hyaline cartilage model develops in 8-12 weeks of development (chondroblasts secrete cartilage matrix)

2. cartilage calcifies and periosteal bone collar forms (chondrocytes poke holes in matrix, matrix calcifies, blood vessels grow towards cartilage, and osteoblasts develop and secrete osteoid)

3. primary ossification center forms in diaphysis (bone development extends towards both epiphyses and bone CT replaces calcified, degenerating cartilage)

4. secondary ossification centers form in epiphyses (bone replaces cartilage and osteoclasts resorb some matrix in diaphysis to create the medullary cavity)

5. bone replaces cartilage (except articular cartilage and epiphyseal plates)

6. lengthwise growth continues until epiphyseal plates ossify and form epiphyseal lines (occurs around puberty into young adulthood)

What is endochondral ossification and what are six steps?

lengthwise growth

it is dependent on the growth of cartilage within the epiphyseal plate

What is interstitial growth and what is it dependent on?

• zone 1: resting cartilage (has small chondrocytes)

• zone 2: proliferating cartilage (rapid cell division, lots of new cells cause the bone to lengthen)

• zone 3: hypertrophic cartilage (chondrocytes enlarge and lacunae walls become thin)

• zone 4: calcified cartilage (minerals are deposited and chondrocytes are destroyed)

• zone 5: ossification zone (osteoblasts deposit bone matrix on calcified cartilage)

What are the five zones of cartilage in the epiphyseal plate responsible for interstitial growth?

bone growth in width

occurs in the periosteum

osteoblasts in the periosteum deposit bone matrix which increases the diameter of the bone

osteoclasts resorb some of the bone matrix, creating an expanding medullary cavity

What is appositional growth?

disorder that results from a disruption between osteoblast and osteoclast function

characterized by excessive bone resorption and deposition (newly deposited bone is poorly formed)

commonly affects the pelvis, skull, vertebrae, femur, and tibia

What is osteitis deformans?

disorder characterized by the abnormal conversion of hyaline cartilage to bone

long bones of limbs stop growing during childhood, but other bones continue normal growth

results from inadequate endochondral ossification

What is achondroplasia dwarfism?

disorder characterized by the reduction of bone mass, enough to compromise normal function

reduced hormones, age, menopause, smoking, having a family history, sedentary lifestyle, and being Caucasian are risk factors

increased incidence of fractures in wrists, hips, and vertebral column

treatment: prevention (good diet and physical activity while young)

What is osteoporosis?

if someone has undergone chemo and their bone marrow is destroyed/functions abnormally

harvested cells are injected into the bloodstream of the recipient and migrate to the normal locations of red bone marrow

*donor and recipient must be a match

Why would someone need a bone marrow transplant, and how is it performed?

disorder in children characterized by disturbances in growth, hypocalcemia, and bowlegged legs

results from vitamin D deficiency in childhood, caused by deficient calcification of osteoid tissue

What is rickets and what causes it?

a child’s bones have a separate diaphysis and epiphysis

an adult’s bones are fused

How is the age of skeletal remains determined?

the shape of bones can change because of weight-bearing movement and exercise

stress is detected by osteocytes and communicated to osteoblasts (blasts secrete more osteoid which hardens when minerals are deposited)

weight-bearing activities increase bone mass, while removal of mechanical stress decreases bone mass

How does mechanical stress change the shape of bones?

• hypocalcemia

  • decreased blood calcium levels

  • consequences result in overexcitability of muscles and nerves which can cause muscle spasms, seizures, heart rhythm problems, etc.

• hypercalcemia

  • increased blood calcium levels

  • consequences include under excitability of muscles and nerves, which causes weak bones, kidney stones, cardiac arrest, etc.

What is the difference between hypocalcemia and hypercalcemia, and what are their consequences?

PTH is secreted from the parathyroid glands when blood calcium levels are low

it accelerates the conversion of calcidiol to calcitriol in the kidneys

How does parathyroid hormone regulate blood calcium levels?

calcitriol is created in the kidneys

it works by:

• increasing osteoclast activity in bone (to increase blood Ca) [with the help of PTH]

• decreasing amount of Ca excreted in urine (retention of Ca) [with the help of PTH]

• increasing absorption of Ca from small intestine (into the blood)

*low levels of calcitriol can result in rickets

How does calcitriol regulate blood calcium levels?

released from the thyroid gland when Ca levels are high

inhibits osteoclast activity and stimulates kidneys to increase Ca excretion in urine

How does calcitonin regulate blood calcium levels?

it encourages production of IGF, a hormone that stimulates the growth of cartilage in epiphyseal plates

How does growth hormone affect bone growth?

it increases the metabolic rate of bone cells and regulates normal activity in epiphyseal plates

How does thyroid hormone affect bone growth?

they dramatically accelerate osteoblast activity and also promote the growth and closure of the epiphyseal plate

How does estrogen and testosterone affect bone growth?

it increases bone loss and impairs growth at epiphyseal plate in children

How do glucocorticoids affect bone growth?

high levels prevent osteoprogenitor cells from differentiating into osteoblasts

How does serotonin affect bone growth?

1. stress fracture

   1. thin break caused by increased physical activity

2. pathologic fracture

   1. occurs in bone that is weakened by disease

3. simple fracture

   1. broken bone does not penetrate skin

4. compound fracture

   1. one or both ends of the bone pierce overlying skin

List and describe four types of bone fractures

simple: 2-3 months

compound: longer than 3 months

How long does it take simple and compound fractures to heal?

1. a fracture hematoma forms as blood vessels are broken

2. a fibrocartilaginous (soft) callus forms

3. a hard callus forms (created when osteoblasts produce trabeculae)

4. bone is remodeled (hard callus stays for 3-4 months and is then replaced with compact bone)

What are the four steps in bone fracture repair?

the melanin synthesized in the matrix near the hair papillae

genetics can also cause differences in the structure of melanin in hair

hormonal and environmental factors can also influence color

melanin can also slow down production as we age (gray hair) or stop altogether (white hair)

What causes differences in hair color?

produce dark pigments called melanin that determines skin color

What do melanocytes do in the epidermis?

create keratin, a protein that gives structure and durability to skin, hair, and nails

What do keratinocytes do in the epidermis?

also called merkel cells, these cells are sensitive to touch and release chemicals to stimulate sensory nerve endings

What do tactile cells do in the epidermis?

immune cells that help fight infection in the skin

What do dendritic cells do in the epidermis?

hair follicles

round follicles result in straight hair

oval follicles result in wavy hair

flat hair follicles result in curly hair

What determines hair texture?

a disease characterized by softened bones, results from low levels of calcium and vitamin D (in adults)

What is osteomalacia?

these cells can differentiate and help create new skin cells, repair damaged skin, and maintain the skin’s structure

What do stem cells do in the epidermis?

osteoclasts resorb bone tissue and the free phosphate ions enter the blood, just like calcium

How are phosphate levels increased in the body?

they cause epiphyseal plates to close prematurely, resulting in short adult stature

How do anabolic steroids affect bone growth?