Questions and Answers
What primarily accounts for the generally hairless appearance in humans?
What is one of the protective functions of scalp hair?
Which body hairs are known to provide a barrier against foreign matter?
What role do hairs in the nostrils play besides trapping dust?
Signup and view all the answers
What may suggest that hair in certain regions serves an erogenous role?
Signup and view all the answers
What primarily influences hair growth and appearance in humans?
Signup and view all the answers
What is the function of sensory nerves surrounding hair follicles?
Signup and view all the answers
Which of the following statements about individual hairs is correct?
Signup and view all the answers
What is the key distinction between Type I and Type II intermediate filament proteins?
Signup and view all the answers
How many keratin protein chains are estimated to be present in the cross-sectional area of an intermediate filament?
Signup and view all the answers
What type of proteins serves as a matrix or 'cement' surrounding the helical proteins in intermediate filaments?
Signup and view all the answers
What happens to hair when it is wet and heated?
Signup and view all the answers
Which of the following describes the a-helical content of intermediate filament proteins?
Signup and view all the answers
What is the significance of the disulphide bonds in intermediate filament proteins?
Signup and view all the answers
What characterizes the glycine- and tyrosine-rich ('high glycine/tyrosine', or HT) proteins?
Signup and view all the answers
What are the two types of classes identified for intermediate filament proteins?
Signup and view all the answers
What describes the appearance of the medulla when it is present in human hair?
Signup and view all the answers
Which of the following statements about the medulla in human hair is true?
Signup and view all the answers
In which situation is the medulla described as fragmented?
Signup and view all the answers
What is a characteristic of the medulla diameter in human hair as age increases?
Signup and view all the answers
What happens when a mountant used for microscopy displaces the air in the medulla?
Signup and view all the answers
How can the appearance of a double medulla in hair be described?
Signup and view all the answers
What is the typical width of the medulla relative to the hair shaft?
Signup and view all the answers
What occurs when the medulla appears dark during microscopy?
Signup and view all the answers
What is a characteristic of the cortical fusi in human hair?
Signup and view all the answers
Which type of keratin proteins is reported to be more characteristic of paracortical material?
Signup and view all the answers
What distinguishes curly Caucasian hair from straight Mongolian hair?
Signup and view all the answers
What pattern has been reported by Fraser et al. in human hair?
Signup and view all the answers
In which hair type is paracortex primarily found?
Signup and view all the answers
What often misidentifies cortical fusi when viewed under a microscope?
Signup and view all the answers
What is true about the occurrence of cortical fusi along the hair shaft?
Signup and view all the answers
What type of cross-section does very curly Negroid hair exhibit?
Signup and view all the answers
What happens to the fluid in hair cells as they move up the follicle?
Signup and view all the answers
What are the two types of pigments responsible for hair color?
Signup and view all the answers
Where are melanin granules predominantly located in human hair?
Signup and view all the answers
Which of the following statements about greying and white hair is accurate?
Signup and view all the answers
What is the shape and size of melanin granules typically found in hair?
Signup and view all the answers
What happens to the DNA in fully keratinized cortical cells?
Signup and view all the answers
What is the appearance of keratin intermediate filaments in the orthocortex of hair?
Signup and view all the answers
What is the primary role of melanin granules in hair?
Signup and view all the answers
Where are pigment granules typically found in relation to keratin fibrils?
Signup and view all the answers
Study Notes
Hair Follicles in Humans and Primates
- Humans possess a comparable number of hair follicles to other primates despite having fewer follicles than most mammals.
- Many human hair follicles are reduced in size, leading to a less visible hair presence.
- Whales are categorized as truly hairless mammals due to complete follicle loss.
Functions of Hair in Humans
- Hair serves ornamental purposes, similar to a lion's mane; scalp hair provides sun protection.
- Eyebrows and eyelashes are protective, keeping eyes free from dust and moisture.
- Outer ear and anogenital hair prevent foreign matter entry into body orifices.
- Nostril hair moderates incoming air, trapping dust and insects while providing temperature control.
- Hair in regions such as the beard, pubic area, and armpits develops at sexual maturity, indicating potential erogenous functions.
- Hair follicles act as sensory receptors, with numerous nerves around them reacting to touch.
Hair Growth and Individuality
- Hair characteristics, including growth and appearance, are genetically determined.
- Hair can undergo treatments like cutting and dyeing, aiding in forensic comparisons.
- Each hair grows individually, ensuring no two hairs are identical in structure.
Microscopic Structure of Hair
- The medulla may be absent in finer hairs, but when present, it appears irregular and globular.
- Medulla characteristics include continuity or intermittent breaks due to cortical material.
- Child hair usually has a smaller medulla than that of middle-aged or elderly individuals.
Protein Composition of Hair
- Hair incorporates two classes of intermediate filament (IF) proteins, Type I and Type II, with distinct features and molecular weights.
- Polymorphic variations in protein types exist between individuals, demonstrating heritable traits.
- Keratin IFs are formed through the pairing of Type I and Type II proteins, which contribute to hair's tensile strength.
Gentic Expression of Hair Characteristics
- The hair's toughness stems from cross-linking between IF proteins and keratin-associated proteins (KAP).
- Water and heat can temporarily alter hair's properties by disrupting certain chemical bonds.
Hair Pigmentation
- Pigment granules, primarily melanin types (eumelanin for dark colors, phaeomelanin for light colors), determine hair color.
- The distribution of pigment granules is typically higher towards the hair's periphery, where greying hair shows fewer granules.
- Nuclear remnants are found in keratinized hair cells, but original chromatin's DNA is often untraceable post-keratinization.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the fascinating world of hair follicles in humans and their primate relatives. Discover the functions of hair in relation to protection, ornamentation, and sensory reception. This quiz delves into the unique characteristics of hair, its growth, and its role in individual identity.
