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Home , Irregular bone, Lacuna (histology)

Histology of and

Color index : Doctor’s slides Important Extra Objectives :

• By the end of this lecture, the student should describe the microscopic structure, distribution and growth of the different types of: (1) Cartilage. (2) Bone. Cartilage

 Cartilage is a specialized type of connective tissue with a rigid (rubber like)matrix.

 Cartilage is usually nonvascular (avascular).It gets blood from The three types of Cartilage:

1) (most common in the human body)

2)

3)

NOTE: all types of cartilage have collagen type II Perichondrium: (supplies cartilage with O2 and nutrients) Cells ( ): Matrix: Sites: - Homogenous -Foetal skeleton )هيكل العظمي للجنين( Vascular C.T Membrane of 2 layers 1) Young chondrocytes: small and - Basophilic- single (normally it is always - Collagen type -Costal cartilage Hyaline 1) Outer layer: Dense fibrous C.T layer .(irregular collagen singular , never in groups) II2(REMEMBER (connects ribs to cartilage fibers) ALL TYPES OF sternum) “most common” 2) Mature chondrocytes: large and CARTILAGE - articular 2) Inner layer: Chondrogenic (cellular), with single or in groups (cell nests) HAVE surfaces (no -active cells) they secrete cartilage matrix and COLLAGEN TYPE (between bones) give rise to chondrocytes. - Both types are in their lacuna II ) -Nose (space between cytoplasm and - & capsule) Bronchi = lacuna + capsule Very Important note : the outer layer of perichondrium is formed of collagen type I . BUT when we describe the hyaline cartilage and its collagen type we say that the collagen is mainly type II

Elastic Similar to hyaline cartilage. Matrix: Sites: cartilage - Elastic fibers -External ear + collagen -Epiglottis (found type II in larynx it closes the air way when زي الرموش you eat)

Cells (Chondrocytes ): Rows of chondrocytes in their lacuna separated by parallel firbrocartilage bundles of Collagen type 1.(We Matrix: Intervertebral No Perichondrium took in foundation that collagen - Collagen disks. always tend to form bundles) type I Thus it is pinkish red in color. BONE Components of Bones hard because it is calcified (Calcium salts).  Bone is a specialized type of connective 1)Bone cellsv : 4 types tissue with a hard matrix. Functions: a) body support. 2)Bone matrix (calcified tissue): It contains type I collagen fibers. b) protection of vital organs as brain & . c) calcium store. The two types of bone are : 3) It forms bone lamellae and trabeculae 1) Compact bone . 2) Spongy (cancellous( bone. 4) Bone cells Osteogenic Cells: : Bone forming cell : : Bone forming cell Bone forming cell Bone destructive cell Large multinucleated cells In periosteum In periosteum & Branched cells. on bony surfaces , in endosteum . Present singly in Howship’s lacunae. & endosteum (can’t divide) ( when many monocytes are fused lacunae and their together they form the osteoclasts and * (It’s the stem Origin: osteogenic cells branches run in the that’s why they’re multinucleated . ) cell of the canaliculi. They have striated or الن هذه الخلية موجودة في وسط مادة جدا قاسية Function: They secrete ruffled borders .(microvilli ف هي محتاجه تتبادل المواد الغذائية فيما بينها ( bone branchesعن طريق ايادي طويلة اللي هي ال the bone matrix and فقط في المناطق اللي تكون قاعدة (like و هذه االيادي عشان توصل للخلية الثانية محتاجة deposit Ca salts in it تشتغل على العظام زي النفق عشان تمشي فيه اللي هو ال Fate: canaliculi cytoplasm is rich in Fate: change to Origin : osteoblasts . lysosomes Give rise to osteocytes Function: They osteoblasts NO Lacunae maintain the bone Origin: blood monocytes matrix Function: bone resorption. NO Lacunae It is found in the Bone Lamellae: of long bones . Consists of : 1- Haversian Systems (): 1) Periosteum . • Longitudinal cylinders.  Outer fibrous layer • Each is formed of concentric bone lamellae  Inner & a , running in the center. osteogenic • Volkmann’s canals: connect the Haversian layer. canals together. They run obliquely or 2) Endosteum. transversely. 3) Bone lamellae . 4) Bone cells. 2. External Circumferential Lamellae.

Compact Compact bone 3- Internal Circumferential Lamellae. 4- Interstitial Lamellae: between osteons. In is found flat bones & of long bones. It Consists of : 1. Periosteum. 2. Endosteum. 3. trabeculae. • are formed of irregular bone lamellae separated by osteocytes inside lacunae. 4. Many irregular red bone marrow spaces. 5. Bone Cells. Spongy bone Spongy NO HAVERSIAN SYSTEMS (NO OSTEONS). Growth of Cartilage and Bones Appositional growth Interstitial growth (increase in width) (increase in length) Produced by the activity of: Produced by division and activity of: Cartilage In the inner chondrogenic layer Mature Chondrocyte

Appositional growth Growth in length (increase in width) (increase in length) • Is produced by the activity of osteoblasts. • Is produced by the activity of epiphyseal Bone • It leads to increase in width. plate of cartilage.

NOTE: Because the ground substance and ECF in the cartilage are rubbery it gives space for expansion, but in bones the ground substance and ECF are hard so the can not divide in the lacunae because there is no space and hard so it is unable to expand. * EXTRA SLIDE + Extra notes 3 minutes will help you understand the lecture more :) - hyaline = glassy. - Blast = active cell. - Lacunae = spaces. TEAM 435 - Cartilage is usually avascular, but the perichondrium is VASCULAR to supply it. - Mature chondrocytes are the only ones that divide. - Fetal skeleton changes from cartilage to bone during child growth. - Hyaline cartilage is in the joints for making their surfaces smooth and to prevent the friction. - Fibrocartilage receives a very poor blood supply -because it doesn’t have perichondrium- so for example if someone is injured in their intervertebral disk it is almost impossible for it to heal so it is most likely replaced. note that there is no perichondrium so the cell must get its nutrients from neighboring cells. - Spaces inside spongy bones contain bone marrow. - Spongy bones are the main source of bone marrow after old age. (The bone marrow found in the shaft of compact bone is converted into fat). - Function of canaliculi: communication between cells and transport the nutrition into the bone marrow of the cell. (We can find canaliculi only in bone.) - Q: Can we find canaliculi on chondrocyte? NO - Ca is important for muscles contraction. if we were on a diet or the level of Ca in blood decreased for any reason osteoclasts will start to free Ca from bones. So, the Ca level in blood will be raised but in bone will be decreased. (lose its balance) - Bone forming cells: osteogenic, and osteocytes. - Bone destruction cell: osteoclasts. (Osteoclasts are responsible for bone modulation “sculpture” in case of injury, it removes the extra bone tissue after the healing of fracture) - Haversian systems are made of Haversian canals which carry the blood vessels (arteries and veins), nerves, and possibly lymph vessels through it. Around the canals in whorl-like arrangements are the osteocytes entrapped within the bony matrix (concentric bone lamellae). - Volkmann’s canal is not part of the Haversian system, it is only a way to communicate with other Haversian systems - Bones are highly vascular while cartilage is avascular. Remember: bones fractures are dangerous because fractured bones may cut vessels causing hemorrhage SUMMARY 5.Which type of is rich in collagen 9.Fibrocartilage (found in intervertebral QUESTIONS type I? disk ) requires long healing process A)Hyaline cartilage when it’s get injured because the lack of B)Elastic cartilage A)Elastic fibers 1.Cartilage is a specialized type of C.T. with a hard matrix. C)Fibrocartilage B)Perichondrium A)True C)Stroma B)False 6. Elastic cartilage contain ………..fibers . D)Haversian system A)Collagen type 1 2.In Hyaline cartilage, inner chondrogenic layer contains B)Collagen type 2 chondroblasts with lacunae. C)Elastic A)True D)All of the above B)False 7.Appositional growth leads to: 3.The chondrocytes could be …………… which are large and A)Decrease in length found either singly or in groups, or …………… which are B)Increase in length small and present singly only. C) Decrease in width A)Young Chondrocytes – Mature Chondrocytes D) Increase in width B) Mature Chondrocytes – Young Chondrocytes 8. Interstitial growth is produced by division 4.Which of the following is NOT considered a site of hyaline and activity of mature chondrocytes. cartilage? A) True A)Foetal skeleton. B) False B)Costal cartilages. C) Articular surfaces of bones.

D) External ear.

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)B )B )A )D )C )C )D )B )B QUESTIONS

7.Appositinal growth in bone ……. 1.who’s rest in howship lacuna 4.Origin or osteoclasts? A)Produced by osteoblast and lead to increase in length A) A)Lymphocytes B)Produced by osteoblast and lead to increase in width B)Osteocyte B)Macrophages C)Produced by and lead to increase in length C)Monocyte C)Fibroblasts D)Produced by epiphyseal plate and lead to increase in width D)Osteoblast D)Monocytes 8.Osteoclast originate from …… 2.trabeculae found in all bones 5.Compact bone is found in the epiphysis. A)Macrophage A)True A)True B)Monocyte B)false B)False C)Osteogenic cell D)Giant cell 3.…….form bone matrix 6.Haversian Systems (Osteons) are only A)osteoclast found in compact bone. 9.Fibrocartilage (found in intervertebral disk ) requires long healing B)osteocyte A) True process when it’s get injured because the lack of ……. C)osteoblast B) False A)Elastic fibers D)osteogenic cell B)Perichondrium C)Stroma

D)Haversian system

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)B )B )B )A )B )D )C )B )A THANK YOU ! Lecture done by : Team Leaders : Rana Barasain Reema AlOtaibi Reema AlBarrak Faisal AlRabaii Shahad AL Anzan Doaa Walid Contact us on Ghadah Al Muhanna [email protected] Amal Al Qarni Wateen Al Hamoud Weam Babaier