Test 1 Flashcards
appositional growth
outer surface growth that increases diameter of the bone; adding layers of circumferential lamellae
osteogenic cells
stem cells that divide and differentiate into osteoblasts
osteoblasts
produce new bone matrix through OSTEOGENESIS; help convert osteoid to bone
osteocytes
mature bone cells that maintain bone matrix; each one occupies a pocket called a LACUNA
lamellae
thin layers of matrix
canaliculi
narrow passageways that interconnect lacunae and provide a route for nutrient diffusion (the thin strands that radiate from the center of the osteon in compact bone, and small pores in trabeculae in spongy bone)
osteoclasts
- remove bone matrix through OSTEOLYSIS (regulates calcium phosphate levels)
- have 50 or more nuclei
hydroxyapapite
- hard, brittle crystals found in the bone matrix that can withstand compression but not twisting/bending
- when calcium phosphate interacts with calcium hydroxide
bone matrix
- contains inorganic salts (hydroxyapatite, calcium carbonate), collagen fibres
- important for compressive and tensile strength of bones
collagen fibres
strong and flexible (tensile forces)
concentric lamellae
lamellae of each osteon; resembles a target
circumferential lamellae
make up outer ring (covered by periosteum) and inner ring (covered by endosteum) in compact bone
interstitial lamellae
fill spaces in between osteons in compact bone
What is endochronal ossification?
cartilage that makes up the embryo’s skeletal system is gradually replaced by bone
bone formation begins at approximately __ weeks after fertilization
6
steps of endochronal ossification
1) chondrocytes enlarge and die
2) osteoblasts form and cartilage ensheathed by superficial layer of bone
3) blood vessels penetrate centre; PRIMARY OSSIFICATION CENTRE: fibroblasts from blood differentiate into osteoblasts producing spongy bone
4) remodelling/growth; medullary cavity forms; bone gets thicker; metaphysis
5) SECONDARY OSSIFICATION CENTRE: capillaries and osteoblasts enter epiphysis
6) epiphysis filled with spongy bone
7) chondrocytes produce cartilage at epiphyseal side and die at diaphyseal side; osteoblasts replace area with bone and move toward epiphysis
8) puberty; osteoblasts produce bone faster than chondrocytes produce cartilage, epiphyseal cartilage disappears (epiphyseal closure)
interstitial growth
when bone grows in length
In endochondrial growth, what is the original source of osteoblasts?
inner layer of periosteum
epiphyseal cartilage/epiphyseal plate
plate of hyaline cartilage present at each metaphysis, separates epiphysis and diaphysis
epiphyseal line
formed after epiphyseal plate stops producing bone (adult stage)
What roles do osteoclasts and osteoblasts play in calcium maintenance?
- osteoclasts break down bone matrix, releasing calcium into the blood
- osteoblasts (if bound to PTH) can release a hormone that matures osteocytes
PTH (parathyroid hormone)
- binds to osteoblasts leading to osteoclast maturation (encouraging breakdown of bone matrix and release of calcium into blood)
- enhance calcium absorption in intestines
- increase production of calcitriol in kidneys (stimulates calcium absorption in small intestine)
cholecalciferol (vitamin D3)
- synthesized by a steroid compound when deep epidermal cells are exposed to UV radiation
- also obtained through diet
- converted into calcitriol by the liver (stimulating calcium absorption)
How is blood calcium level decreased? (increased bone calcium level)
- C cells in thyroid gland release CALCITONIN
- osteoclast activity reduced
- reduced PTH/calcitriol = less absorption
- inhibits absorption of calcium ion in kidney
Long bones grow ____ while flat bones grow ____.
long bones grow endochrondrally, flat bones grow intramembranously
axial skeleton
skull, thorax, vertebral column
appendicular skeleton
upper limbs, lower limbs, pectoral girdle, pelvic girdle
nutrient foramen
“window” through the bone that allows blood vessels and nutrients to enter
medullary cavity
hollow shaft in the diaphysis that contains bone marrow, lipid deposits, blood vessels and nutrient deposits
osteoid
matrix that surrounds cells (osteoblasts)
What structures are present in compact bone but not spongy bone?
central canals and osteons
Organization of lamellae in compact vs. spongy bone
- compact bone: concentric lamellae arranged in osteons
- spongy bone: forms struts and plates known as trabeculae
Where is bone marrow found?
in the medullary cavity and spongy bone
hair matrix
basal cells that divide to produce hair; contain melanocytes
hair papilla
small peg of connective tissue filled with blood vessels and nerves
hair medulla
centre of hair matrix; cells not dividing here; soft keratin
arrector pili muscles
smooth muscles attached to the hair follicle that causes the hair to stand upright when contracting
Describe the phases of hair growth
1) active phase: hair grows (2-5 years)
2) regression: moving into resting phase (1-2 weeks)
3) resting phase: hair loses attachment to the follicle (5-6 weeks
4) reactivation: club hair is shed, replacement begins to be produced
dermal papillae
- project into epidermis (epidermal ridges)
- increase surface area for attachment of epidermis to dermis
sebaceous glands
- secrete oil (sebum) into the hair follicle
- holocrine secretion: cells become packed with secretion and burst, releasing contents
sebum
- mixture of triglycerides, cholesterol, electrolytes and proteins
- lubricates hair, moisturizes skin, inhibits bacteria growth
apocrine sweat glands
- produce sticky, cloudy, potentially smelly secretion
- found in armpits, groin, nipples (limited areas)
- may be a part of olfactory communication
- merocrine secretion: contents released by exocytosis
myoepithelial cells
- squeeze sweat glands to discharge secretion
eccrine/merocrine sweat glands
- produce a watery secretion containing electrolytes
- most areas of the skin
- thermoregulation, excretion, antibacterial
- merocrine secretion: contents released by exocytosis
Why do fingers wrinkle in water?
- in water, electrolytes are diluted
- blood vessels constrict around glomus bodies (components of the dermis involved in thermoregulation) to control electrolyte amounts
- glomus bodies are found in the dermis and when they contract, it pulls the epidermis towards the dermis causing wrinkles
cutaneous membrane
consists of the epidermis and dermis
subcutaneous layer
- aka hypodermis
- contains fatty tissue (adipose tissue)
- where vaccines go
- not part of the integument but separates it from deeper structures
papillary layer
- layer of the dermis
- highly vascularized (blood vessels) areolar (connective) tissue
- capillaries, lymphatic vessels, sensory nerve fibres
reticular layer
- dense mesh of irregular connective tissue
- collagen and elastic fibres
- contains accessory organs (like hair follicles and sweat glands)
functions of the integumentary system
- protection
- production of melanin and keratin
- excretion
- thermoregulation
- synthesis of vitamin D3
- lipid storage
- sensory reception
arrector pili muscle
- attached to hair follicle
- raises hair when contracting
- involuntary
- raising hair traps heat in animals with a lot of hair (response to cold), makes the animal look larger (response to danger)
thin skin vs. thick skin
thin skin: - 4 strata - approx. 0.08 mm thick - covers most of the body thick skin: - 5 strata (lucidum) - palms and soles of the feet - approx. 0.5 mm thick
name and briefly describe the layers of the epidermis
- stratum corneum: densely packed dead keratinized cells connected by desmosomes; takes 7-10 days to go from basale to corneum and can remain for 2 weeks until shed
- stratum lucidum: “clear layer” that separates stratum corneum from deeper layer in THICK SKIN ONLY; flattened cells filled with proteins keratin and keratohyalin
- stratum granulosum: “grainy layer” that has 3-5 layers of keratinocytes (make keratin); darker in colour; no cell division
- stratum spinosum: “spiny layer” with 8-10 layers of keratinocytes bound by desmosomes; contains dendritic cells that act in immune response
- stratum basale: deepest layer of the epidermis; contains basal cells that divide; have melanin, sensation cells; more organized
osteoprogenitor cells
differentiate into osteoblasts
How is skin colour determined?
by HOW MUCH melanin is produced to protect keratinocytes (not by the number of melanocytes)
melanin
brown/yellow-brown/black pigment produced by melanocytes
albinism
when cells lack the enzyme needed to produce melanin
carotene
orange-yellow pigment found in epidermal cells (mostly in stratum corneum of light skin people)
melanosomes
- carry melanin
- travel from melanocytes to keratinocytes, transferring melanin which temporarily colours keratinocyte until melanosomes are destroyed by fusion with lysosomes
How does melanin transfer differ in lighter skin vs. darker skin
- lighter skin: transfer occurs in stratum basale and spinosum so the more superficial layers lose pigmentation
- darker skin: transfer also occurs deeper in stratum granulosum, melanocytes are more active, pigmentation is darker and more persistent
melanocyte
- located in stratum basale
- manufacture melanin from the amino acid tyrosine
What protects the skin (keratinocytes) from UV radiation?
melanin
basal cell carcinoma
- most common form of skin cancer
- caused by overexposure to UV (sunlight)
- metastasis is highly unlikely
malignant melanoma
- cancerous melanocytes grow rapidly
- metastasize through entire lymphatic system (very bad!!)
subpapillary plexus
network of blood vessels that supply blood to capillaries in the epidermis and dermis
free nerve endings
- found in epidermis
- touch, pressure
tactile discs
- found in deepest layer of epidermis
- texture, steady pressure
tactile corpuscles
- found in papillary layer of the dermis
- fine touch, pressure and vibrations
lamellar corpuscles
- found in the dermal and subcutaneous layers
- deep pressure, vibrations
bulbous corpuscles
- found in the reticular layer of the dermis
- pressure, stretching
proximal vs. distal
- proximal: toward the centre of body/point of attachment
- distal: away from centre of body/point of attachment
lateral vs. medial
- lateral: away from midline
- medial: toward midline
superior vs. inferior
- superior: at high level; above
- inferior: at lower level; below
superficial vs. deep
- superficial: near the surface
- deep: toward internal, away from the surface
posterior/dorsal vs. anterior/ventral
- posterior/dorsal: back
- anterior/ventral: front, belly surface
cranial/cephalic vs. caudal
- cranial/cephalic: towards the head
- caudal: toward the tail
frontal plane
- parallel to long axis
- separates anterior and posterior
sagittal plane
- parallel to long axis
- separates left and right
- midsagittal: separates body into equal left and right
- parasagittal: unequal sections
transverse plane
- perpendicular to long axis
- separates superior and inferior portions of the body
- aka cross section
