Lips Flashcards

Study the anatomy of the upper and lower lips, including their layers, muscles, landmarks, blood supply, innervation, and lymphatic drainage.

Card 1 of 30Question

What are the lips?

Two mobile musculomembranous folds surrounding the oral fissure and forming the anterior boundary of the oral cavity.

In This Section

1. What are the lips?

Two mobile musculomembranous folds surrounding the oral fissure and forming the anterior boundary of the oral cavity.

2. What are the two anatomical subdivisions of the lips?

The upper lip and lower lip, also called the labium superius and labium inferius.

3. What are the principal layers of the lips from superficial to deep?

Skin, subcutaneous connective tissue, muscular layer, submucosa, and oral mucosa.

4. Which muscle forms the principal muscular core of the lips?

The orbicularis oris muscle.

5. What is the primary action of the orbicularis oris muscle?

Closure, compression, and protrusion of the lips.

6. Which cranial nerve provides motor innervation to the muscles of the lips?

The facial nerve (cranial nerve VII), through its facial branches.

7. Which branches of the facial nerve primarily supply the orbicularis oris muscle?

The buccal and marginal mandibular branches, with overlapping and variable contributions.

8. What is the vermilion of the lips?

The reddish transitional zone between the external facial skin and the internal oral mucosa.

9. What is the vermilion border?

The visible junction between the vermilion and surrounding facial skin.

10. Why does the vermilion normally appear red?

Its relatively thin epithelium allows the underlying superficial capillary network to show through.

11. Why are the lips particularly susceptible to drying?

The vermilion lacks the abundant sweat and sebaceous glands found in ordinary skin.

12. What is the philtrum?

The vertical midline depression on the external surface of the upper lip between the nose and vermilion border.

13. What is the Cupid's bow?

The characteristic double-curved contour of the central upper vermilion border.

14. What are the oral commissures?

The lateral junctions where the upper and lower lips meet at the corners of the mouth.

15. What is the modiolus of the mouth?

A fibromuscular convergence of facial expression muscles near each oral commissure.

16. Which mucosal folds connect the inner surfaces of the lips to the gingiva?

The superior and inferior labial frenula.

17. What type of epithelium lines the internal surfaces of the lips?

Predominantly nonkeratinized stratified squamous epithelium.

18. Which salivary glands are found within the submucosa of the lips?

Numerous minor labial salivary glands, which are predominantly mucous-secreting.

19. Which arteries provide the principal blood supply to the lips?

The superior and inferior labial arteries, usually branches of the facial artery.

20. Where do the superior and inferior labial arteries typically travel?

Within the substance of the lips, near the junction of the orbicularis oris muscle and labial mucosa.

21. How do the labial arteries communicate across the midline?

The corresponding right and left labial arteries anastomose to form vascular arcades.

22. Which veins provide the principal venous drainage of the lips?

The superior and inferior labial veins, draining primarily into the facial veins.

23. Which nerve provides general sensory innervation to most of the upper lip?

The infraorbital nerve, a branch of the maxillary division of the trigeminal nerve (V2).

24. Which nerve provides general sensory innervation to most of the lower lip?

The mental nerve, a terminal branch of the inferior alveolar nerve from the mandibular division of the trigeminal nerve (V3).

25. Where does lymph from the central portion of the lower lip primarily drain?

To the submental lymph nodes.

26. Where does lymph from the upper lip and lateral portions of the lower lip primarily drain?

To the submandibular lymph nodes.

27. Which embryological prominences form the upper lip?

The fused medial nasal prominences form the central portion, while the maxillary prominences form the lateral portions.

28. Which embryological prominences form the lower lip?

The paired mandibular prominences of the first pharyngeal arch.

29. What developmental abnormality typically causes a unilateral cleft lip?

Failure of fusion between the maxillary prominence and medial nasal prominence on the affected side.

30. What is the characteristic effect of facial nerve paralysis on the lips?

Weakness of lip closure and movement, potentially causing drooping of the oral commissure and difficulty retaining saliva.