Anatomy Exam One

Babler's Anatomy at UT Austin 446L

What type of tissue is adipose tissue?

connective

What are the two types of adipocytes?

white and brown

what are the function of adipocytes?

to synthesize and store triglycerides

how does adipose tissue function as an endocrine organ?

It secretes Leptin, a hormone that binds to cells in the brain (hypothalamus) to signal satiety

what are the 3 places where fat comes from?

chylomicrons from the intestines, VLDLS from the liver, and synthesized in the cell from glucose

what are the 2 ways fat can be mobilized?

the autonomic nervous system + hormonal signalling, both cause lipase to break down triglycerides

what are the characteristics of white adipose tissue?

unilocular, nucleus against membrane, energy storage site, synthesize and store triglycerides

what leads to the redistribution of white adipose tissue?

puberty/sex hormones

what are the characteristics of brown adipose tissue?

multilocular, smaller with many droplets of fat, central nuclei, for heat production, with many mitochondria

at what life stage do humans carry the most brown fat?

infancy

what condensation leads to the formation of cartilage bone models?

mesenchyme

what differentiates from the mesenchymal cells?

chondroblasts

progenitor cells can become either or

osteoblasts or chondroblasts

when does bone start to develop?

when the progenitor cells become osteoblasts

where is the primary centre of ossification?

the diaphysis of a developing bone

as the cartilage matrix begins to calcify, what happens to the cartilage cells?

they become hypertrophic and die, forming a cavity

what migrates into the cavity formed by dying cartilage cells?

periosteal cells

what is syndactyly?

digits are not formed normally

what is Apert's syndrome?

one disease that causes syndactyly

what kind of tissue is cartilage?

connective

cartilage consists of ___blasts which start to produce ___

"chondro", ECM

what is a lacunae

a cell nest

where do chondrocytes reside?

lacunae

95% of cartilage is made of?

ECM

what is in the ECM in cartilage?

ground substance (proteoglycans, glycosaminoglycans), collagen, and elastic fibres

cartilage is vascular/avascular

avascular

cartilage is innervated/not innervated

not innervated

what is the perichondrium?

a sheath of dense connective tissue

what are the two layers of the perichondrium?

inner layer which is chondrogenic and the outer layer which is fibrous

the inner layer of the perichondrium is the source of

cartilage cells

the outer layer of the perichondrium is the source of

fibroblasts which produce collagenous fibres and blood vessels

what are the two functions of the perichondrium?

growth and repair of cartilage

where is the perichondrium found?

the perimeter of elastic cartilage and hyaline cartilage

what two cartilage lack perichondrium?

fibrocartilage and articular cartilage

what are the three types of cartilage?

hyaline, elastic, and fibrocartilage

what is hyaline cartilage?

most common and mostly type 2 collagen, bone development and growth at the epiphyseal growth plate, also the site of interstitial growth

where is hyaline cartilage found?

trachea, bronchi, larynx, nose, ends of ribs, long bones

what is the epiphyseal plate?

where bone growth occurs

what is endochondral ossification?

growth at the proximal and distal ends of long bones

what is elastic cartilage?

elastic fibres and lamellae which does not calcify

where is elastic cartilage?

external ear, eustachian tube, epiglottis, larynx

what do the chondrocytes in elastic cartilage look like?

large, hypercellular

what is elastic cartilage surrounded by?

perichondrium

what is fibrocartilage?

in dense CT and mostly type 1 collagen

fibrocartilage has more/fewer chondrocytes

fewer

fibrocartilage is a mix of ____ and ____

fibres and hyaline cartilage (type 1, 2)

what is the main purpose of fibrocartilage?

shock absorber

what are the two forces that fibrocartilage withstands?

compression and shear force

examples of areas that have fibrocartilage

intervertebral discs, mandibles, pubic bone, sternum, knee

what happens at the epiphyseal growth plate?

chondrocytes undergo hypertrophy, die, become calcified, and osteoblasts lay down a new layer of bone, the plate is displaced away from the centre of the diaphysis and the length of the bone increases

the perichondrium

a sheath of dense connective tissue surrounding most cartilaginous structures, forms an interface between the cartilage and tissues supported by the cartilage, carries blood supply and some nerves

what is the structure of bone?

bone tissue + fat + hemopoietic tissue + blood vessels + nerves + hyaline cartilage

what does hemopoietic mean?

making blood

what is bone tissue made of?

calcified bone matrix or ECM and 3 bone cells

what are the two bone tissue layers?

compact cortical bone which is dense and spongey cancellous or trabecular bone

_blast

active and producing

_cyte

maintenance

_clast

breaking down

why is bone spongey?

to increase surface area to quickly add or remove calcium

what are the four functions of the bone?

mechanical support, protection, mineral homeostasis, and haematopoiesis

the function of cortical bone is

mechanical and protective

the function of trabecular bone is

metabolic

how do you make bone matrix?

collagen and ground substance are calcified

what is the major mineral?

calcium phosphate in the form of hydroxyapatite crystals

osteoblasts

secrete type 1 collagen and osteoid, promotes calcification by secreting alkaline phosphatase

what is osteoid?

initial unmineralized matrix

what shape is an active osteoblast?

cuboidal

osteocytes

trapped osteoblasts which occupy lacunae and make dendritic processes through canniculi and communicate with others, they secrete growth factors and stimulate other cells, live for ~10 years

osteoclasts

form giant multinucleated cells in contact with the surface of the bone and are differentiated from progenitor cells, more similar to macrophages (not true bone cells), they enhance Ca2+ release and break down old or damaged bone, they reside in resorption bays or Howship lacunae, produce a ruffled border while active

periosteum

surrounds bones, provides components for healing and repair, has 2 layers

what are the two layers of the periosteum?

outer layer is dense fibrous Ct, which is vascularized and innervated and the inner layer is the source of osteoprogenitor cells

how are collagen fibres of the periosteum arranged to the surface of the bone?

the ligaments and tendons enter the matrix at an angle (perforating or Sharpey's fibres)

what is the endosteum?

a single layer of osteoprogenitor cells and osteoblasts, small amount of CT, thinner than periosteum only one cell layer, the point of contact with the bone marrow > bone formation!

cartilage vs bone

cartilage contains chondrocytes embedded in the ECM and mostly type 2 collagen, while bone contains osteocytes and has a mineralized ECM and mostly type 1 collagen; both have perichondrium/osteum of two layers

at the microscopic level, what are the two types of bone?

primary/woven/immature and secondary/lamellar/mature

what is the woven bone?

the first to appear in development and fracture repair but the collagen fibres are disorganized and less mineralized

what is the lamellar bone?

replaces primary bone and is more organized (more communication between osteocytes) and has more perforating canals (increases blood vessels and contact with periosteum)

what is bone remodelling?

old osteons are resorbed by osteoclasts which form tunnel like cavities through old bone, those tunnels are invaded by osteoprogenitor cells and blood vessels which secrete new osteoid and form new lamellae; this traps osteocytes and eventually forms new osteon

what are the two mechanisms of osteogenesis?

endochondral and intramembranous bone

what is endochondral osteogenesis?

mesenchymal cells condense and form cartilaginous bone models which will be replaced by ossified tissue

what is intramembranous osteogenesis?

bone forms from condensed mesenchyme which differentiate into osteoblasts without a cartilage model (flat bones are formed this way)

where does the interchange of blood and bone calcium happen?

cancellous (compact) tissue

appositional growth

along the outer edge

interstitial growth

divides in existing areas

What is the ECM made out of?

The ___ contain different combinations of long protein fibers (collagen and elastic fibers) and ground substance, a complex of anionic hydrophilic proteoglycans, glycosaminoglycans (GAGs), and multiadhesive glycoproteins (laminin, fibronectin, and others).

What is mesenchyme?

a tissue developing mainly from the middle layer of the embryo, the ___derm. _______ consists largely of viscous ground substance with few collagen fibers.

Mesenchymal cells have _____ nuclei with ____ chromatin and ____ nucleoli.

large, fine, prominent

What are fibroblasts?

They are key cells in connective tissue proper.

What do fibroblasts do?

They synthesize and secrete collagen (the most abundant protein of the body) and elastin, which both form large fibers, as well as the GAGs, proteoglycans, and multiadhesive glycoproteins comprising the ground substance.

What do plasma cells do?

They make antibodies- y-shaped proteins that target antigens (toxins or bacteria).

What do eosinophilic leukocytes do?

They modulate allergic/vasoactive reactions and defend against parasites.

What do neutrophilic leukocytes do?

Phagocytosis of bactera.

What do macrophages do?

Phagocytosis of ECM debris, antigen presentation and processing, secretion of growth facotrs, cytokines (chemical messengers made of proteins), etc.

What do mast cells and basophilic leukocytes do?

They make pharmacologically active molecules like histamines.

What do adipocytes do?

They store neutral fats.

What is the difference between fibroblasts and fibrocytes?

Fibroblasts are highly active with high metabolic activity while fibrocytes are relatively inactive and “mature”.

Active fibroblasts have more _____ and irregularly _____ cytoplasm. They have ____ rough endoplasmic reticulum and a ___-_______ golgi apparatus.

abundant, branched, much, well-developed.

What are growth factors?

They are a family of proteins which influence cell-growth and differentiation.

Myofibroblasts are involved in ___ ________. They have a form of ____ found in smooth muscle cells.

wound healing, actin

What is the purpose of adipose tissue?

It serves to cushion and insulate the skin and other organs. Made of cells specialized to store lipid as neutral fats or less commonly, to produce heat