Connective Tissue Flashcards
What are some common features of connective tissues:?
- few cells (“hole” in ECM - lacuna)
- mostly ECM
What makes up the Extracellular Matrix (ECM)?
- ground substance
- protein fibers
What are the 3 types of protein fibers found in ECM?
- collagen (most common)
- elastic
- reticular
What determines the properties of the ECM and examples of this?
proportions
1. hard - calcified in bone
2. gel-like - loose connective in cartilage
3. fluid - in blood
(properties vary on how much you have of each protein fiber - bone vs ear)
Collagen fiber features:
- high tensile strength
- flexible
- like a rope
Elastic fiber features:
- low tensile strength
- recoils
- like a rubber band
What is the most abundant protein in the body?
collagen
What is the structure of collagen
triple helix structure (long thick rods)
How to build collagen?
chain -> triple helix -> colalgen fiber -> collagen fibril
- one polypeptide chain (primary)
- 3 chains into triple stranded collagen (triple helix)
- many triple helix come together to make a collagen fiber
- collagen fibril - lots of collagen fibers
What is ground substance made of?
proteoglycan molecules with glycosaminoglycan (GAG) chains (like bristles)
Why are you 1 cm taller in the morning than in the evening?
The negative charge of GAG chains in cartilage reacts with water and absorbs it throughout the night. As you walk around the water gets squeezed out and you get shorter.
Function of water in cartilage:
- add firmness to ground substance
- contribute to joint lubrication
What are two specialized cells found in cartilage?
- fibroblasts
- macrophages
What do fibroblasts do?
synthesis collagen & elastin fibers - secrete hyaluronic acid
What do macrophages do?
engulf damaged cells & pathogens
What are the non-universal categories of cartilage?
- General - loose & fibrous
- Specific - cartilage, bone, blood, hemopoietic tissue
What are the three types of loose connective tissue?
- mesenchyme
- adipose tissue
- areolar tissue
What is mesenchyme tissue?
embryonic tissue
- gives rise to all other connective tissue
- mesenchymal cells (but no tissue) in adults
What is adipose tissue?
store fat
- energy storage, padding, insulation
What are the two types of adipose tissue and their functions/locations?
- energetic white fat (typical- belly, hypodermis)
- thermogenic brown fat (catabolism gives off heat - babies with small surface area to volume)
What is areolar tissue?
“packing peanuts”
- cushion & support organs, nerves
- lots of collagen & elastin fibers
- in papillary layers of dermis
What are the 2 types of fibrous connective tissue?
- dense regular - parallel collagen fibers
- dense irregular - strength and support from multiple directions
What are three examples of dense regular connective tissues?
- aponeuroses
- ligaments (bone to bone - plywood)
- tendons (muscle to bone - rope)
What are two examples of dense irregular connective tissues?
- periosteum (around the bone)
- reticular layer (suede inside of leather)
What are the 3 types of cartilage?
- hyaline cartilage
- elastic cartilage
- fibrocartilage
What are some locations of the 3 cartilage types?
- hyaline - ribs, joints of limbs, hip, nose
- elastic - ears, epiglottis
- fibro - spine discs, knees, pubic symphysis
Describe hyaline cartilage
- most common cartilage
- relatively weak
- forms embryonic skeleton (fontanelles)
Describe elastic cartilage
- elastic fiber is flexible & resilient
- weakest
- least common cartilage
Describe fibrocartilage
- in areas of high stress.
- strongest
- lots of collagen & little ground substance
What are some of the main structures of bone? (6)
- Osteon made of
- Concentric lamella which have
- Osteocytes in
- Lacuna with
- Canalculi coming off
- Central/Haversian canal going through middle
What are the characteristics of bone tissue?
- few osteocytes
- mostly hard, calcified matrix
What are the components of the calcified matrix of bone?
- bone is a composite tissue
1. collagen - 1/3 - adds flexibility
2. CaPO4 & CaCO3 - 2/3 - hard, but brittle
What is the structure of bone matrix?
CaPO4 as crystals of hydroxyapatite and CaCO3 bound to collagen triple helix
What are the types of bone cells? (3)
- osteoblasts
- osteocytes
- osteoclasts
Describe osteoblasts
builds bone tissue matrix - get trapped in matrix (lacuna) become osteocyte
Describe osteocytes
mature cell which maintains matrix
Describe osteoclasts
break down bone matrix to be recycled - use HCL & lysosomes
Why is the directionality of collagen fibers different between lamellae?
to prevent microwear and tear so it won’t continue all the way through osteon (like cracks in concrete)
What connects central canals of one osteon to another?
Volkmann’s canals
How does bone resist fracturing?
- bone is a composite material (collagen & CaPO4)
- collagen orientation changes (directionality of collagen fibers)
