Histology 🔬 Flashcards
(124 cards)
1
Q
what is the definition of cartilages?
A
It is a specialized type of connective tissue
2
Q
what are the characters of cartilages?
A
- The cartilage is avascular, no nerves or blood and lymphatic vessels.
- Has firm or rubbery matrix
- Usually covered by perichondrium.
3
Q
what are the functions of cartilages?
A
Firm matrix:
- Allows the tissue to bear mechanical stresses without permanent distortion
- Supports soft tissues especially in respiratory system.
In joints:
- Shock-absorbing because it is resilient.
- Smooth surface Preventing rubbing of bones against each other.
- It helps connect tendons and ligaments to bones.
- Essential for growth, development of bone in growing children.
4
Q
what is the structure of cartilage?
A
- Chondrocytes (Cartilage cells).
- Cartilage matrix.
- Fibers.
5
Q
what are the types of cartilage?
A
Hyaline Cartilage: it appears translucent pale blue (i.e. hyaline = glassy in fresh state)
Yellow elastic fibrocartilage: It is a yellow colour in fresh state
White fibrocartilage: It is white colour in fresh state.
6
Q
what is the most common type of cartilage?
A
Hyaline Cartilage
7
Q
what are the sites of Hyaline Cartilage?
A
- Forms majority of the fetal skeleton.
- Articular Surface of bones.
- Costal Cartilage in the thoracic cage.
- Respiratory passages: Nose, Trachea, Bronchi
- Laryngeal cartilages (Thyroid and cricoid)
8
Q
what is the structure of Hyaline Cartilage?
A
- Perichondrium.
- Chondrocytes.
- Matrix.
9
Q
what is the definition of Perichondrium?
A
It is a vascular connective tissue membrane which covers the cartilage except at the articular surface of joints.
10
Q
what is the Perichondrium formed of?
A
Formed of 2 layers:
1) Outer fibrous layer.
2) Inner chondrogenic layer.
11
Q
what is Outer fibrous layer of perichondrium formed of?
A
Formed of fibrous connective tissue rich in collagen type I, fibroblasts and blood vessels.
12
Q
what is the function of Outer fibrous layer of perichondrium?
A
- Blood supply and nourishment of cartilage cells
- Site for attachment of muscles.
13
Q
what forms the Inner chondrogenic layer of perichondrium?
A
It is formed of cartilage forming cells (chondroblast) which can divide and differentiate into chondrocytes which secrete the cartilage matrix.
14
Q
what is the function of Inner chondrogenic layer of perichondrium?
A
new cartilage formation during growth or repair, (as chondroblasts secrete matrix, then change into chondrocytes).
15
Q
what is the shape of chondroblasts?
A
Oval young cells with cell processes.
16
Q
site of chondroblasts
A
Present in perichondrium.
17
Q
function of chondroblasts
A
Precursors of chondrocytes.
18
Q
what are the types of cartilage cells?
A
There are 2 types of cartilage cells (Chondrocytes):
1. Young chondrocytes.
2. Mature (old) chondrocytes.
19
Q
compare between young & old chondrocytes according to
- site
- structure
- no. inside their lacunae
- function
A
20
Q
what are cell nests?
A
a group of cells that are present inside single lacunae and separated by thin partitions of matrix
21
Q
what are the characteristcs of the matrix of cartilage?
A
- Firm or rubbery in consistency.
- Avascular but it allows diffusion of oxygen and nutrients from blood vessels of perichondrium to reach the chondrocytes.
- There is concentration of the cartilage matrix around each lacuna which is rich in glycosaminoglcans and poor in collagen, this zone called the territorial or capsular matrix.
- It is homogenous as collagenous fibers have the same refractive index of the amorphous substance.
- It is basophilic due to high content of chondrotin sulphate.
- The basophilia is markedly increased around lacunae and cell nests.
- It is stained metachromatically by Toluidine blue → appear purple.
- It shows strong PAS positivity.
22
Q
structure of hyaline cartilage matrix
A
23
Q
what is Territorial matrix?
A
The darker staining matrix immediately surrounding the lacuna of chondrocytes
24
Q
what is Interterritorial matrix?
A
Is the matrix that occupies the majority of space between chondrocytes.
25
what are the general feautures of Yellow elastic fibrocartilage?
- Fresh elastic cartilage has a yellow colour due to presence of elastin in the elastic fibers.
- The most flexible and stretchable type of cartilage.
- It can be stained by standard elastic stains e.g. orcein & verhoeff’s stains.
26
what is the most flexible and strechable type of cartilage?
yellow elastic fibrocartilage
27
what stains Yellow elastic fibrocartilage?
orcein & verhoeff’s stains.
28
# 4E
what are the sites of Yellow elastic fibrocartilage?
- Ear Pinna
- External auditory meatus.
- Eustachian tube
- Epiglottis
29
what is the structure of Yellow elastic fibrocartilage?
It is identical to hyaline cartilage except that:
- The matrix contains an abundant network of fine elastic fibers in addition to collagen type II fibrils which responsible for elasticity and flexibility of this type.
30
what are the general characters of White fibrocartilage?
- It is white in colour in fresh state.
- It is the strongest type of cartilage that resists stretch due to presence of collagen fibers
- It has alternating layers of hyaline cartilage matrix and thick layers of dense collagen fibers oriented in the direction of functional stresses
31
what is the strongest type of cartilage?
White fibrocartilage
32
what are the sites of White fibrocartilage?
1. Intervertebral disc.
2. Symphysis pubis.
3. Semilunar cartilage of knee joint (mensci)
4. Terminal parts of tendons.
33
what is the structure of White fibrocartilage?
It differs from hyaline cartilage in:
- It is not covered by perichondrium as it is usually a transitional layer between hyaline cartilage and tendon, but it is surrounded by dense C. T. It receives the nourishment and O2 supply from the blood vessels of the surrounding C.T.
**Matrix:**
- It is acidophilic because it contains a great number of coarse type I collagen fibers arranged in bundles.
**Chondrocytes:**
- Are arranged in rows in lacunae (single or in pairs) between collagen bundles.
34
compare between the 3 types of cartilage in terms of:
- appearence
- site
- perichondrium
- matrix
- collagen fibers
35
compare between appositional growth & interstitial growth of cartilage in terms of:
- definition
- direction of growth
- mechanism
- result of growth
36
what is achondroplasia?
- is a form of short-limbed dwarfism due to a genetic mutation in the gene Responsible of converting cartilage to bone (a process called ossification), particularly in the long bones of the arms and legs.
37
what is osteoarthritis?
- degenerative change in the articular cartilages of both opposing bone ends of a joint leading to their rubbing with pain sensation.
38
what is **disc degeneration and prolapse**?
- degenerative change in intervertebral disc between 2 vertebrae, A slipped disc occurs when the outer covering of the disc (annulus) tears and the internal gel (nucleus) herniates, causing the gel to press on the nerve root
39
what is the definition of bones?
Bone is a highly specialized variety of C.T
40
what are the functions of bones?
1. It forms the skeleton.
2. Muscles attachment.
3. Protection of soft organs as brain.
41
what are the constituents of bones?
1. Bone cells
2. Bone Matrix
3. Periosteum
4. Endosteum
42
site of osteogenic cells **(osteoprogenitor cells)**
- Inner osteogenic layer of periosteum.
- Endosteum.
- Bone marrow cavities
43
LM of osteogenic cells (osteoprogenitor cells)
- They are flat cells with central flat nuclei
- pale basophilic cytoplasm.
44
EM of osteogenic cells (osteoprogenitor cells)
Rich in ribosomes and rER.
45
what are the functions of osteogenic cells (osteoprogenitor cells)?
They are capable to divide and give osteoblasts (bone forming cells) during:
1) Growth of bone.
2) Healing of fracture bone.
46
what is the origin of osteoblasts?
Activated osteogenic cells
47
Sites of osteoblasts (Bone forming cells)
- Activated inner osteogenic layer of periosteum.
- Endosteum.
- Walls of bone marrow spaces.
48
LM of osteoblasts
- Oval branched cells with few processes
- Oval, eccentric, open face nuclei.
- Deep basophilic cytoplasm
49
EM of osteoblasts
- ribosomes, rER, well-developed Golgi apparatus & mitochondria
50
what are the functions of osteoblasts?
- Bone formation (matrix secretion).
- Bone calcification:
1. Alk phosphatase enz → facilitates deposition of Calcium
2. Pyrophosphatase enz →inhibit pyrophosphate.
3. Matrix vesicles: buds from cell membrane, store Ca.
- Change into osteocytes.
51
what is the origin of osteocytes?
They are mature osteoblasts.
52
what are the sites of osteocytes?
can't divide and present singly inside lacunae between bone Lamellae
53
LM of osteocytes
- oval, branched cells with oval, central nuclei.
- The cytoplasm is slightly basophilic and rich in Alk. phosphatase
- Osteocytes can’t divide, so present singly in each lacuna.
54
EM of osteocytes
- rER, ribosomes, Golgi apparatus, and many cytoplasmic microtubules.
- The cells are present inside lacunae between bone lamellae
- They are connected with one another by processes passing through bone canaliculi which connect adjacent lacunae together.
- These cell processes intercommunicate with one another by gap junctions.
- The gap junctions between the processes allow the electrolytes to pass freely from one cell to the other.
55
what are the functions of osteocytes?
- The form bone matrix and vesicles rich in enzymes to preserve the integrity of the bone matrix and maintaining its inorganic components.
- They are related to mobilization of Ca+ from the bone to the blood in times of need.
56
what is the origin of osteoclasts?
Arise from blood cells called monocytes.
57
what are the sites of osteoclasts?
**(where resorption takes place):**
- Bone marrow spaces.
- Medullary cavities.
- Endosteum.
- Each cell lies in a shallow cavity called (Howships Lacuna)
58
LM of osteoclasts
- large irregular cell (20-30 um)
- Multinuclated (4-50) nuclei
- Cytoplasm is foamy acidophilic.
- The cells have striated or brush border facing the bone surface.
59
EM of osteoclasts
The osteoclast shows the following 4-zones:
1) Ruffled or striated zone.
2) Clear Zone.
3) Vesicular Zone.
4) Basal Zone.
60
what are the functions of osteoclasts?
- Bone resorption during ossification causing remodeling of bone
- They remove bone debris during ossification and after healing of bone fracture.
61
what are the general characteristics of bone matrix?
- It is hard or solid in consistency.
- It is rich in blood supply.
62
what are the components of bone matrix?
**consists of organic and inorganic components:**
63
what are the divisions of periosteum?
It is formed of 2 layers:
**1) Outer fibrous layer:**
- It is rich in collagenous fibers, blood vessels and fibroblasts.
**2) Inner osteogenic layer:**
- It is formed of osteogenic spindle-shaped cells.
- These cells when stimulated during growth or healing of fracture can change into osteoblasts.
64
what are the functions of periosteum?
1) Provide attachment for muscles, ligaments and tendons.
2) Provide bone with blood supply and nourishment.
3) Inner osteogenic layer is important for formation of bone during its growth & after its fracture.
65
what are the characters and sites of endosteum?
- It is a vascular C.T. membrane
- lines the inner surface of the bone, bone marrow cavities and Haversian canals.
66
what is the structure of endosteum?
- Rich in osteogenic cells, osteoblasts, osteoclasts and blood vessels
- Endosteum doesn't contain osteocytes
67
what are the functions of endosteum?
1. It supplies bone with blood supply & nourishment.
2. bone formation and resorption during growth & healing after fracture.
68
what are the types of bones?
compact and cancellous
69
what is the definition of compact bones?
Solid like ivory with no apparent holes i.e. compact.
70
what are the sites of compact bones?
1. Shaft of long bones.
2. Outer & inner tables of flat bones of the skull.
3. Outer covering of the vertebrae & ribs.
71
what is the structure of compact bones?
1. Periosteum.
2. Endosteum.
3. Bone matrix.
4. Bone cells.
72
what forms the matrix of compact bones?
The matrix is formed of lamellae of calcified osteoid tissue in which osteocytes are embedded.
73
what are the patterns found in the matrix of compact bones?
**1. Outer (external) circumferential lamellae:**
- they are present under the periosteum and parallel to it.
**2. Inner (Internal) circumferential Lamellae:**
- These lamellae are present under the endosteum and parallel to the medullary bone cavity, which contains the bone marrow
**3. Concentric Lamellae**
- (It is formed of 4-20 cylinders of concentric bone lamellae arranged around Haversian canal) .
**Interstitial (Inter-Haversian) Lamellae:**
- They are formed of calcified osteoid tissue present between Haversian systems.
- Osteocytes are irregularly arranged between these lamellae.
74
what is the definition of Haversian system (Osteon)?
It is the structural unit of the bone.
75
what is the structure of Haversian system?
It is formed of:
- Haversian Canal: It runs parallel to the longitudinal axis of the bone
- Concentric bone lamellae: It is formed of 4-20 cylinders of concentric bone lamellae
- Osteocytes: They are found inside their lacunae in between the bone lamellae.
76
what are Volkman's Canals?
These are transverse or oblique canals.
77
what do Volkmann canals connect?
They connect Haversian canals together and with periosteal or endosteal blood vessels
78
what are the characters of Volkmann canals?
They are lined with osteogenic cells and contain blood vessels.
79
what is the structure of perforating fibers of sharpy?
These are calcified collagenous fibers
80
what are the functions of perforating Fibers of sharpy?
Fixing the periosteum to the bone.
81
what is cancellous bone?
It looks like – sponge with Many holes, so called spongy bone
82
what are the sites of cancellous bone?
1. Epiphysis of long bones.
2. Central part of flat bones of the skull.
3. Bodies of vertebrae & sternum.
4. Young embryonic bone.
83
what is the structure of cancellous bone?
- It is formed of bone lamellae in the form of irregularly arranged bars or trabeculae which branch and anastomose.
- The bone trabecular are separated by bone marrow spaces of irregular shape and size.
- The bone marrow spaces are filled with active red bone marrow.
84
what is ossification?
It is the process of bone formation, which leads to its growth.
85
what are the methods of Bone ossification?
1) Intramembranous ossification: It occurs in mesenchymal membranes.
2) Intracartilagenous ossification: It occurs in cartilage model.
86
what is intramembranous ossification?
Mesenchymal connective tissue is transformed into spongy bone.
87
where does intramembranous Ossification Occur?
Flat bones of the skull, face and clavicle.
88
what are the steps of intramembranous ossification?
1- UMCs condense forming a primary ossification center.
2- UMCs change into osteoblasts, which start bone formation.
3- Osteoblasts synthesize bone matrix.
4- UMCs in the spaces between trabeculae give rise to bone marrow.
5- Mesenchymal tissue at the surface gives rise to the periosteum.
89
what is intra-cartilaginous ossification? **(growing end of long bone)**
It is a type of ossification by which cartilaginous model is
replaced by bone.
90
where does intra-cartilaginous ossification occur?
Epiphyseal plates of the cartilage.
91
what are the stages of intra-cartilaginous ossification?
1. Stage of resting cartilage
2. Stage of proliferation
3. Stage of maturation and hypertrophy
4. Stage of calcification
5. Stage of Invasion
6. Spongy bone formation
7. Stage of remodeling and compact bone formation
92
Stage of resting cartilage
chondrocytes embedded in their matrix.
93
Stage of proliferation
chondrocytes divide and give large umber of flat chondrocytes.
94
Stage of maturation and hypertrophy
- The chondrocytes grow in size.
- lacunae widen and separated by thin bars of matrix.
95
Stage of calcification
- The chondrocytes secrete Alk. Phosphatase .
- The matrix becomes impermeable → cut off nutrients → death of the cells leaving empty lacunae separated by thin bars calcified matrix.
96
Stage of Invasion
- The empty spaces are invaded by vascular mesenchymal tissue.
- Some monocytes change into osteoclasts → hole → vascular bud.
97
stage of Spongy bone formation
- Some osteogenic cells → osteoblas → form trabeculae of spongy bone.
98
Stage of remodeling and compact bone formation
- Osteoclast destruct bars of bone.
- Osteoblast arrange around blood vessles and form concentric lamellae → haversian system
99
introduction to muscle tissue
▪ One of the four basic tissues of the body.
▪ It is responsible for the different types of movements.
▪ 3 Types of muscle present in our bodies:
- Skeletal muscle fibers.
- Cardiac muscle fibers.
- Smooth muscle fibers
100
what are the general characteristics of skeletal muscle fibers?
- Striated (show transverse striation by light microscope).
- Voluntary in its action (under control of will).
- Do not branch.
101
what are the sites of skeletal muscle fibers?
1) All muscles attached to the skeleton.
2) Eye muscles.
3) Tongue
4) Pharynx & larynx.
102
structure of muscle tissue
▪ It is formed of elongated cells called muscle fibers.
▪ Has plasma membrane named Sarcolemma
▪ Its cytoplasm named Sarcoplasm
▪ Its smooth endoplasmic reticulum named Sarcoplasmic reticulum
103
what is the skeletal muscle formed of?
1) Muscle fiber.
2) Connective tissue elements (Muscle sheath).
104
connective tissue elements of skeletal muscle fibers
**Epimysium:**
- Dense C.T surrounds the entire muscle.
**Perimysium:**
- Dense C.T. divides the muscle into bundles (fasciculus).
**Endomysium:**
- Loose C.T. surrounds the individual muscle fiber.
105
what is the function of connective tissue in skeletal muscle?
1. Connects the fibers with each other.
2. Carries blood vessels, nerves & lymphatics
3. Give an attachment to bone& cartilage.
106
LM of skeletal muscle fiber
**L.S**
- The muscle fibers are parallel to each other.
- Shape: Single elongated cell.
- Nuclei: Multiple, peripheral, flattened nuclei.
- Sarcoplasm: acidophilic with transverse striation.
**T.S**
- Shape: polyhedral.
- Nuclei: only seen in some fibers.
- Sarcoplasm: acidophilic with myofibrils.
107
EM of skeletal muscle fiber
The muscle fiber contains:
1) Myofibrils.
2) Mitochondria& ribosomes.
3) Myoglobin pigment.
4) Transverse tubules (TT)
5) Glycogen granules.
6) sER (sarcoplasmic reticulum).
108
what is the definition of myofibrils (Sarcostyle)?
Contractile elements running parallel to each other and longitudinally arranged in the sarcoplasm of the skeletal muscle fiber.
109
structure of myofibrils (Sarcostyle)
- The myofibril has regularly (Equally spaced) alternating light (I- band) and dark (A-band).
- The dark band of one myofibril is present beside those of adjacent myofibrils giving the cross striation seen by light microscope.
- Each dark band is divided at its center by a light disc called H-zone.
- Each light band is divided at its center by a dark line called Z-line (Z- disc).
110
what is the definition of sarcomere?
The functional contractile unit of skeletal myofibrils. It is the area lies between the two Z-lines.
111
what is the structure of sarcomere?
- Includes a whole A band and two halves of I band on either side.
- Contains myofilaments.
112
what is the definition of myofilaments?
It is the protein molecule of myofibrils, it is thread-like filaments and are longitudinally arranged in the myofibrils.
113
What are the types of myofilaments?
thin & thick
114
compare between thin filaments and thick filaments in terms of
- Diameter
- Extension
- Ends
- Protein Content
115
appearance of sarcomere regions
- The I band appear light as it contains the thin actin filaments only.
- The A band appear dark as it contains both actin and myosin filament.
- The H- zone appear light as it contains myosin filaments only.
- The Z-line is dark as it contains other types of filaments and due to interdigitation of actin filaments.
116
what is a triad formed of?
1. One transverse tubule (T.T)
2. Two terminal cisternae of sarcoplasmic reticulum
117
characters and site of transverse tubules of the skeletal muscle
- The sarcolemma (Cell membrane of muscle fiber) sends tubular invagination named transverse tubules (T.T.) into the fibers to penetrate it and encircle the sarcomeres.
- It lies at the Z line
- It lies in close contact with the sarcoplasmic reticulum.
118
Terminal cisternae of sarcoplasmic reticulum of skeletal muscle fiber
- The ends of the sarcoplasmic reticulum tubules dilate into two wide tubules named terminal cisternae (one on each side of the T.T.).
119
what is the role of triad in contraction?
- The transverse tubules responsible for moving action potentials to the inner region of the muscle cell.
- Nerve impulses are transmitted to the terminal cisternae through the T.T. of the triads.
- The terminal cisternae release Ca++ ions into the myofibrils leading to muscle contraction.
120
what are the general characters of smooth muscle fibers?
- Non-striated.
- Involuntary in its action.
- Do not branch.
121
what are the sites of smooth muscle fibers?
1. Wall of blood vessel.
2. Viscera of systems (GIT, urinary, respiratory).
122
LM of smooth muscle fibers
**Shape:** Single elongated short cell.
**Nuclei:** Single, central, flattened nuclei.
**Sarcoplasm:** Non striated
123
EM of smooth muscle fibers
- Show dense bodies.
- Mitochondria, Golgi saccules and ribosomes.
- Intermediate filaments (desmosomes and vemintin)
- Actin and myosin.
124
what is the function of the smooth muscles?
1. Maintain partial tonic contractions (regulate luminal size in hollow organs).
2. Produce rhythmic contractions or peristaltic movements e.g. digestive system
