Histology of Bone and Other Connective Tissue

Question 1

Type of tissue composed of cells relatively few and far apart, with abundant intercellular substance containing tissue fluid and fibers

Answer 1

Connective tissue

Question 2

Three major components of connective tissue

Answer 2

1. fibers (collagenous, reticular, elastic)
2. ground substance
3. connective tissue cells

Question 3

Type of connective tissue that:

• binds bones and other tissues to each other
• is composed of alpha-polypeptide chains
• is located in the tendon, ligament, skin, cornea, cartilage, bone, blood vessels, gut, intervertebral disc

Answer 3

Collagenous tissue

Question 4

Type of connective tissue that:

• allows organs like arteries and lungs to recoil
• is composed elastic microfibrils and elastin
• is located in the extracellular matrix, respiratory tract, blood vessels, walls of the ligamentum flava

Answer 4

Elastic tissue

Question 5

Type of connective tissue that:

• forms a scaffolding for other cells
• is composed of type III collagen fibers and agyrophilic fibers that support hematopoetic and lymphoid organs
• is located in the liver, bone marrow, lymphatic organs

Answer 5

Reticular tissue

Question 6

Type of collagenous tissue that mainly supports epithelial tissue, acting as SUPPORT STRUCTURES which are normally under friction/pressure; this also has an important role in providing a medium for oxygen and nutrients to diffuse from capillaries to cells, and carbon dioxide and waste substances to diffuse from cells back into circulation

Found in the papillary layer of the dermis, most of the hypodermis

Answer 6

Loose connective tissue (or areolar tissue)

Question 7

Type of collagenous tissue that mainly RESIST STRETCHING AND TEARING and also mainly provides a medium for oxygen and nutrients to diffuse from capillaries to cells, and carbon dioxide and waste substances to diffuse from cells back into circulation

Found in capsules and linings: organ capsules, periosteum, perimyseum, perichondrium, perineurium, the reticular layer of the dermis

Answer 7

Dense irregular tissue

Question 8

Type of collagenous tissue that forms ORGANIZED STRUCTURES

Found in tendons, ligaments, aponeuroses, specialized organs of the cornea

Answer 8

Dense regular tissue

Question 9

Most abundant, most numerous protein in the human body

Answer 9

Collagen

Question 10

Type of collagen found in dermis, bone, tendon, fibrocartilage

Answer 10

Type I

mnemonic: sk1n, bONE

Question 11

Type of collagen found in hyaline cartilage and elastic cartilage

Answer 11

Type II

mnemonic: carTWOlage

Question 12

Type of collagen found in reticular fibers, used in wound healing

Answer 12

Type III

mnemonic: reTHREEculin

Question 13

Type of collagen found in basal lamina

Answer 13

Type IV

mnemonic: BASEMENT membrane; basement below the FOUR/”floor”

Question 14

Type of collagen found in the fetal membrane

Answer 14

Type V

Question 15

Type of collagenous tissue in which macrophages are most abundant

Answer 15

Loose connective tissue (or areolar tissue)

Question 16

Stem cell precursor of most connective tissue cells

Answer 16

Mesenchymal cell

Question 17

Cell responsible for IMMEDIATE hypersensitivity reactions

Answer 17

Mast cell

Question 18

Normal connective tissue cell with the characteristic signet ring appearance

Answer 18

Adipose cell

Question 19

Normal cell that can be recognized by the arrangement of its heterochromatin granules:

• seen in areas of inflammation
• produces antibodies
• arrangement of granules give a cartwheel or spokewheel appearance to the nucleus

Answer 19

Plasma cell

Question 20

Hardest tissue of the body, histologically classified according to its collagenous organization as woven or lamellar

Answer 20

Bone

Question 21

Cell that secretes the ground substance in connective tissue

Answer 21

Fibroblast

Question 22

Bone matrix is mostly made up of a composite material incorporating the inorganic mineral calcium phosphate in this specific chemical arrangement that is responsible for a bone’s rigidity

Answer 22

Calcium hydroxylapatite

Question 23

The elastic protein which improves fracture resistance of bone

Answer 23

Collagen type I (or ossein)

Question 24

Type of bone that composes the hard outer layer of bones, made up of the Haversian system of multiple interconnected microscopic columns called osteons

Answer 24

Cortical bone (or compact bone)

Question 25

Main unit of the Haversian system of cortical bone

Answer 25

Osteon

Question 26

4 parts of the osteon

Answer 26

1. Haversian canal (CENTRAL CANAL) 2. lamellae (CONCENTRIC LAMELLAE) 3. osteocytes & osteoblasts (CELLS IN MULTIPLE LAYERS) 4. canaliculi (CANALS) (mnemonic: 4C's of Cortical/Compact bone)

Question 27

Type of bone that makes up the internal tissue of the bone, characterized as an open, cell porous network; here, thin formations of osteoblasts covered in endosteum create an irregular network of spaces known as trabeculae

Answer 27

Cancellous bone (or trabecular/spongy bone)

Question 28

This is the space found in cancellous/trabecular/spongy bone in which bone bone marrow and hematopoietic stem cells that give rise to platelets, red blood cells and white blood cells are located

Answer 28

Trabecula (pl. trabeculae)

Question 29

Histologic type of bone characterized by a haphazard organization of collagen fibers: - mechanically weak - smaller number of randomly oriented collagen fibers, but forms quickly - initial formation that follows a bone fracture, later replaced by its more mechanically stronger counter-part - predominant bone type in Paget's disease of the bone

Answer 29

Woven bone (or fibrous bone)

Question 30

Histologic type of bone filled with a more numerous and orderly organiztion of collagen fibers: - mechanically stronger - formation slower than its weaker and less organized counter-part - first appearance in humans in the fetus during the third trimester - collagen fibers parallel to other fibers in the same layer, allowing for the creation of parallel columnar units of bone called osteons

Answer 30

Lamellar bone

Question 31

Process in which woven bone initially forms to correct a bone fracture, but is later resorbed and replace by lamellar bone

Answer 31

Bony substitution

Question 32

At right angles, connects osteon to another osteon

Answer 32

Volkmann canal

Question 33

Depression in the bony matrix in which osteoclasts can be found

Answer 33

Howship lacuna (pl. Howship lacunae)

Question 34

Bundles of periosteal collagen fibers that penetrate the bone matrix, binding the periosteum to bone

Answer 34

Sharpey fiber

Question 35

Hormone that decreases calcium level: - osteoblastic (inhibits osteoclast activity) - also inhibits renal tubular cell reabsorption of calcium (and phosphate), allowing excretion through the urine

Answer 35

Calcitonin (or thyrocalcitonin)

Question 36

2 types of cells in the thyroid gland and their main hormonal secretions

Answer 36

1. Follicular cell = thyroid hormone (T3, T4) | 2. Parafollicular cell (or C cell) = calcitonin (thyrocalcitonin)

Question 37

2 types of cells in the parathyroid gland and their main hormonal secretions

Answer 37

1. Chief cell = parathyroid hormone (PTH) | 2. Oxyphil cell = unknown function

Question 38

Hormone that increases calcium level: - osteoclastic (promotes osteoclast activity) - reabsorption of Ca in the distal tubules and the collecting ducts of the kidney - inhibits reabsorption of phosphate from the tubular fluid; phosphate ions form water-insoluble salts with calcium, thus, a decrease in the plasma phosphate increases the amount of ionized calcium in the blood - stimulation of the conversion of 25-hydroxy vitamin D into 1,25-dihydroxy vitamin D (calcitriol), which is released into the circulation; calcitriol stimulates calcium uptake from the intestine via calbindin

Answer 38

Parathyroid hormone

Question 39

Bone mineralization disorder in which the bone progressively softens due to reduced vitamin D, which may result from a reduced osteoblast activity while osteoclast activity remains normal or elevated

Answer 39

Osteomalacia

Question 40

Juvenile bone mineralization disorder from a gross deficiency of vitamin D, calcium, and phosphorus

Answer 40

Rickets

Question 41

Bone mineralization disorder resulting in bone fragility and fractures

Answer 41

Osteoporosis

Question 42

Disease of ossification centers of bone in children

Answer 42

Osteochondrosis

Question 43

The main glycosaminoglycans in bone and cartilage

Answer 43

Chondroitin sulfate

Question 44

The main glycosaminoglycans in the umbilical cord

Answer 44

Hyaluronic acid

Question 45

The main glycosaminoglycans in the skin

Answer 45

Dermatan sulfate

Question 46

The main glycosaminoglycans in the aorta, lung, liver, basal laminae

Answer 46

Heparan sulfate

Question 47

The main glycosaminoglycans in the cornea

Answer 47

Keratan sulfate

Question 48

The 2 main component of the extracellular matrix GROUND SUBSTANCE and their main functions

Answer 48

1. Glycosaminoglycans (GAGs) - lubrication, water-retention | 2. Proteglycans - ECM "filler", shock-absorber, resists pressure forces

Question 49

Mechanism of fetal bone development: - involves the rudimentary flat bones of the skull, scapular, and manubrium - highly involved in fracture healing - does not involve the development of cartilage (development is from mesenchymal stem cell DIRECTLY to bone)

Answer 49

Intramembranous ossification

Question 50

Mechanism of fetal bone development: - involves the rudimentary flat bones of the skull base, pelvis, vertebrae, extremities - involves the development of a cartilage model (later strengthened and ossified)

Answer 50

Encochondral ossification (or intracartilagenous ossification)

Question 51

Type of growth, part of the intracartilagenous ossification of fetal bone development where there is a continuous mitosis of chondrocytes, accompanied by secretion of ECM, creating a cartilage model growing in LENGTH

Answer 51

Interstitial growth

Question 52

Type of growth, part of the intracartilagenous ossification of fetal bone development where the cartilage model begins to grows in THICKNESS due to the addition of more ECM on the peripheral cartilage surface, which is accompanied by new chondroblasts that develop from the perichondrium

Answer 52

Appositional growth

Question 53

Zone of osteogenesis where condrocytes divide

Answer 53

Resting zone

Question 54

Zone of osteogenesis where there is lengthening of the cartilage model

Answer 54

Zone of proliferation

Question 55

Zone of osteogenesis where mature chondrocytes undergo hypertrophy with vacuoles accumulating glycogen

Answer 55

Zone of hypertrophy

Question 56

Zone of osteogenesis where the matrix between cells, left behind by degenerating chondrocytes, become filled with hydroxyapatite

Answer 56

Zone of calcification

Question 57

Zone of osteogenesis containing differentiating osteoblasts

Answer 57

Zone of ossification

Question 58

Type of cartilage found in the pubic symphysis, the anulus fibrosus of intervertebral discs, menisci and the TMJ: - also present at the tendon bone interface, where there is a transition from soft tendon to uncalcified then calcified fibrocartilage before becoming bone - only type to contain type I collagen as well as type II - loosened by relaxin during pregnancy (loosens the pubic symphysis) - NO perichondrium - flexible and tough due to its fibrous tissue - elastic due to its cartilagenous tissue

Answer 58

Fibrocartilage

Question 59

Type of cartilage present in the outer ear, Eustachian tube, and epiglottis: - contains bundles of elastic fiber networks and collagen fibers - with perichondrium - singly, isogenous arrangement of cells - principal protein is elastin - great flexibility, withstands repetitive bending while maintaining shape

Answer 59

Elastic cartilage (or yellow cartilage)

Question 60

Type of cartilage found in most joint surfaces: - most common/abundant cartilage - most widely distributed - with perichondrium - singly, isogenous arrangement of cells - made of an abundant matrix of chondrocytes

Answer 60

Hyaline cartilage