a&p exam #3

Hair production begins at bulging base of a hair follicle (hair bulb):

• Hair papilla 

• Hair matrix

Hair papilla

• Contains capillaries and nerves

• Hair color produced by melanocytes at the hair papilla

Hair matrix

• Layer of dividing basal stem cells 

• Produces hair structure

• Pushes hair up and out of skin

Medulla

• Central core

• Flexible soft keratin

Cortex

• Middle layer

• Stiff hard keratin

• Provodes strength, bulk, and color

Cuticle

• Protective surface layer

• Overlapping, shingle-like hard keratin

Hair growth cycle:

• Growing hair

  • Firmly attached to matrix

  • Grows for 1-6 years

• Club hair

  • Not grow for 1-4 months

  • Atatched to an inactive follice

• New hair growth cycle

  • Follicle becomes active

  • Prodcues new hair

  • Club hair is shed

Vellus hairs

• Soft, fine

• Cover body surface

Terminal hairs

• Heavy pigmented

• Head, eyebrows, and eyelashes

• After puberty: armpits, pubic area, etc.

Exocrine glands:

Sebaceous (oil) glands

• Secrete sebum (oils)

• Inhibits bacteria

2 types of sebacceous (oil) glands

• Associated with hair follicles

• Sebacceous follicles

  • Discharge directly onto skin surface

Apocrine Sweat glands

• Found in armpits, around nipples, and groin

• Secrete products into hair follicles

• Produce sticky, cloudy secretions

• Break down and cause odors

Merocrine (eccrine) sweat glands

• Discharge directly onto skin surface

• Precipitation

• 98-99% water (with some salts & organic compounds)

• Widely distributed on body surface 

Functions of merocrine sweat glands

• Cool skin

• Excrete water, electrolytes

• Flush microogranism, harmful chemicals from skin

Exocrine gland: Mammary glands

• Produce milk

Exocrine gland: Ceruminous glands

• Produce cerumen (earwx)

• Protect the eardrum

Nails:

dead cells packed with keratin

Nail function: 

• Protect fingers and toes

• Limits distortion of finger/toes

• Tool

Nail body:

• Visible portion of the nail

• Covers the nail bed

Nail production: Growth occurs in……

the nail root, underneath skin near the bone

Lunula:

• Pale crescent at the base of the nail

• Thick epithelial tissue blocking blood vessels

Primary function of the skeletal system:

1. Support

2. Storage

   • Minerals (calcium)

   • Lipids (yellow bone marrow)

3. Blood cell production

4. Protection

5. Leverage (force of motion)

Bone shapes:

• irregular

• Long bones

• Short bones

• Flat bones

Irregular bones:

• Have complex shapes

• Ex: spinal vertebrae, pelvic bones

Long bones:

• Long and thin

• Ex: found in arms, legs, hands, feet, fingers and toes

Short bones:

• Small and thick

• Ex: Ankle and wrist bones

Flat bones:

• Thin with parallel surfaces

• Ex: found in skull, sternum, ribs and scapulae

Long bone structure:

• Diaphysis

• Epiphysis 

• Metaphysis

• Characteristics of dense vs spongy bone

Diaphysis:

• Bone shaft 

• Heavy wall of compact bone, or dense bone 

• Central cavity called marrow (medullary) cavity

Epiphysis:

• Wide part at each end

• Articulation w other bones

• Mostly spongy bone

• Covered with compact bone

Which bone structure has a heavy wall of compact bone, or dense bone?

Diaphysis

Which bone structure is mostly spongy bone?

Epiphysis

3 main components of bone tissue:

1. matrix

2. Specialized cells

3. Membranes

Components of bone tissue: Dense matrix contains…

Calcium salt deposits around collagen fibers

Components of bone tissue: Specialized cells..

• 3 main types (osteoblasts, osteoclasts, and osteocytes)

• Only 2 percent of bone mass

• Thin outer layer (periosteum) and inner (endosteum) membranes

What is the thin outer bone membrane called?

Periosteum

What is the thin inner bone membrane called?

Endosteum

Bone matrix:

Minerals

• Two-thirds of bone matrix is made from calcium phosphate, some other minerals

• Hard, but brittle

One-third of bone matrix is protein fibers (collagen), and strong, but flexible. What is this?

Matrix protiens

Ostgenic or osteoprogenitor cells:

 are stem cells in the bone that play a prodigal role in bone repair and growth

Osteoblasts:

• Produced from stem cells 

• Immature bone cells

  • Produce new bone by secreting osteioid

  • Mostly collagen w some other proteins

  • Not yet calcified

• Promote deposition of calcium salts

Osteoblasts surrounded by bone become what?

osteocytes

Osteocytes are mature…..

 Bone cells

• Live in lacuna “pit”

Osteocytes are between layers (________) of matrix……

 Lamellae

What are osteocytes connected by?

 Canaliculi 

• Cytoplasmic extensions into lamellae

• Pathways to blood vessels 

  • Exchange nutrients and wastes

Osteocytes has two major functions what are they?

1. Maintain matrix locally

   1. Recycle calcium salts

2. Assist in matrix repair

What are osteoclasts?

Giant, Multinucliate cells

What do osteoclasts do?

• Secrete

  • Acids

  • Protein-digesting enzymes

• Dissolve bone matrix and release stored minerals (osteolysis)

What are osteoclasts derived from?

Stem cells that produce macrophages

What is an osteon?

 The basic organizing unit of compact bone

Osteon has what in the middle and what does it contain?

Central canal, which contains blood vessels

Osteon: Lamallae form layers around what?

Central canal

Perforating canal, and its function…

• Perpendicular to the central canal

• Function: Carry blood vessels into bone and marrow

Components of spongey bone:

• Trabeculae

• Red bone marrow

• Yellow bone marrow

Spongy bone does not have (2 things)?

• Osteons

• Blood vessels 

  • Canaliculi lead to surface of bone 

Spongy bone, the matrix forms an open network of….

Trabeculuae

• Struts and plates of networks

The spaces between trabeculae are filled with?

 Red bone marrow

Red bone marrow:

• Has blood vessels

• Forms red blood cells, white blood cells, platelets

• Supplies nutrients to osteocytes

Yellow bone marrow:

• Stores fat

Periosteum (bone membrane):

• Covers bone outer surface

  • Expect in enclosed join capsules

• Outer fibrous layer

• Inner cellular layer

Functions of periosteum

1. Isolates bone from surrounding tissues

2. Connects bone to tendons and ligaments

3. Route for nerves, blood and lymphatic vessels

4. Bone growth and repair

Endosteum (bone membrane):

• Covers inner surfaces 

  • Lines marrow cavity

  • Cover spongy trabeculae

  • Lines central canals

Endosteum has an incomplete…

• Cellular layer

  • Oseoblasts, stem cells, osteoclasts

Endosteum is active in…

Bone growth, repair, and remodling

Bones are initially formed through what?

 Ossification

Ossification

Process of replacing other tissue with bone

Two main forms of ossification

1. Endochondral ossification

2. Intramembranous ossification

Endochondral ossification

• Ossifies bone from hyaline cartilage

• Most bones

• Has 5 steps

Step 1 of endochondral ossification:

Chondrytes enlarge and die

Step 2 of endochondral ossification:

Blood vessels grow around cartilage and osteoblasts form bone on outside of shaft

Step 3 of endochondral ossification:

Blood vessels penetrate central cartilage

• Fibroblasts in blood become osteoblasts

• Build spongy bone in primary ossifiaction center

Step 4 of endochondral ossification:

Remodeling

• Osetoclasts create cavity

• Epiphysial cartilage or plate continues to grow bone length-wise

Step 5 of endochondral ossification:

Capillaries penetrate epiphyses

• Create secondary ossification centers with spongy bone

• Epiphyeseal cartilage reduced to thin layer

  • Add new cartilage until end of puberty

• All internal cartilage replaced by bone when growth ends

Epiphyseal lines after puberty:

Epiphyseal plate place by bone

Appositional growth:

• Widening of bone during growth

  • Osetoblasts in periosteum add bone

  • Osteoclats enlarge narrow cavity

• Can continues in adulthood due to activities (exercise, etc.)

Intramembraneous ossification produced from?

The dermis

Intramembranous ossification produces?

Dermal bones

• Skull 

• Mandible (lower jaw)

• Clavicle (collarbone)

Intramembranous ossification are what?

• Osteoblats produced from stem cells in dermis

  • Produce bone in ossification centers

Intramembranos ossification: what spreads from ossification centers?

Bone spreads

• Surrounds blood vessels 

During Intramembranous ossification what occurs?

Remodeling

Bone remodling:

• Bone is replaces continually recycled and replaced

  • At membrane and osteocytes

Bone remodling involves?

 osteocytes, osteoblasts, and osteoclasts

Remodeling in the adult skeleton:

• Tears down damaged, worn bone, and replaces with new bone

• Replaces mineral reserves

Bone remodeling turn over rate varies, if deposition is greater than removal

• Bones get stronger 

• Exercise to adapt to stress

Bone remodling turn over rate varies, If removal is faster than replacement:

• Bones deteriorate

• Inactivity, disease, diet

Calcium regulation:

Calcium ion in the blood

Calcatonin and paratyroid hormone affects what?

Bones

• Where calcium is stores
  

Digestive tract

• Where calcium is absorbed 

Kidneys 

• Where calcium is excreted

Parathyroid hormone is produced by?

Parathyroid gland in the neck

Parathyroid hormone (PTH) increases….

Calcium ion in blood by:

• Stimulatig osteoclasts

• Increasing intestinal absorption of calcium

• Decreasing calcium excretion at kidneys

Calcitonin is produced by what?

Thyroid

Calcitonin does what?

Decreases calcium ion levels in blood by:

• Inhibiting osteoclasts

• Decreasing intestinal absorption of calcium

• Increasing calcium excretion at kidney

What are fractures?

• Crack or breaks in bones

• Caused by physical stress

Fractures are repaired in 4 steps:

1. Fracture hematoma

2. Callus formation

3. Spongy bone formation

4. Compact bone formation

Step 1 fracture repair, Fracture hematoma:

• Clot produced by extensive bleeding

• Establishes a fibrous network

• Bone cells in the area die

Step 2 fracture repair, Callus formation:

• Cells of the endosteum and periosteum divide and migrate into fracture zone

  • Create cartilage and spongy bone

• Calluses stabilize the break

  • External callus surrounds break

  • Internal callus develops in medullary cavity

Step 3 fracture repair, Spongy bone formation:

• Spongy bone replaces cartilage and dead bone, connecting to live bone

Step 4 fracture repair, Compact bone formation:

• Osteoblasts and osteoclasts remodel the fracture for up to a year

• Reduce bone calluses

9 major types of fractures

Transverse: breaks across long axis

Displaced:  improper bone alignment

Comminuted:  shattered bone 

Spiral: twisting stress

Greenstick: only one side of shaft is broke

Compression: vertebrae subject to extreme stress

Epiphyseal: transverse fracture along epiphyseal cartilage, can stop growth

Colles: breaking of distal part of radius, cushion a fall

Pott’s: ankle fracture, affects both tibia and fibula 

Osteopenia:

• Loss of bone mass, naturally occurs with age

• Epiphyses, vertebrae, and jaws affected most

Osteoporosis:

• Severe bone loss

• Affects normal function