Cell specialisation - specialised cell examples Flashcards
What is the primary function of alveoli in the lungs?
To provide maximum surface area for gas exchange by diffusion.
What is the thickness of the alveolar walls?
One cell thick.
What are the two different cell types that make up the alveolar epithelium?
- Type I Pneumocytes
- Type II Pneumocytes
What is the role of Type I Pneumocytes?
To maximize the rate of gas exchange by providing a short diffusion distance.
What is the distance between air in the alveoli and blood typically?
Less than 0.5μm.
What is the function of Type II Pneumocytes?
To secrete a solution that coats the epithelium of the alveoli.
What percentage of the alveolar epithelium is made up of Type II Pneumocytes?
Around 5%.
What is contained in the solution released by Type II Pneumocytes?
Pulmonary surfactant.
What are the characteristics of pulmonary surfactant?
- Hydrophobic tails
- Hydrophilic heads
What is the main function of pulmonary surfactant?
To reduce surface tension, maintaining alveolar shape and preventing collapse.
How does the solution secreted by Type II Pneumocytes aid gas exchange?
It allows oxygen to dissolve before diffusing into the blood and helps carbon dioxide diffuse out.
What are the three types of muscles in the body?
- Skeletal muscle
- Cardiac muscle
- Smooth muscle
What is a key feature of striated muscle?
It has a stripy appearance when viewed under a microscope.
What surrounds striated muscle fibres?
A single plasma membrane called the sarcolemma.
What are myofibrils?
Bundles of actin and myosin filaments that slide past each other during muscle contraction.
What is the role of the sarcoplasmic reticulum (SR) in muscle fibres?
To store calcium and convey signals using protein pumps.
What are T-tubules?
Deep tube-like projections of the sarcolemma that run close to the SR.
What is a unique property of cardiac muscle?
It is myogenic, meaning it can contract without external stimulation.
What connects cardiac muscle fibres to each other?
Specialised branched connections called intercalated discs.
What is the primary function of mitochondria in cardiac muscle?
To provide ATP needed for continual contraction.
What are the special features of sperm cells?
- A haploid nucleus
- An acrosome with hydrolytic enzymes
- Many mitochondria
- A flagellum
What is the purpose of the acrosome in sperm cells?
To aid entry into the ovum through the zona pellucida.
What surrounds the egg cells (ova)?
A jelly layer called the zona pellucida.
What is the function of follicle cells surrounding the ova?
To nourish and protect the ova.
